ehci.c

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/*
 * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#include <byteswap.h>
#include <ipxe/malloc.h>
#include <ipxe/pci.h>
#include <ipxe/usb.h>
#include <ipxe/init.h>
#include "ehci.h"

/** @file
 *
 * USB Enhanced Host Controller Interface (EHCI) driver
 *
 */

/**
 * Construct error code from transfer descriptor status
 *
 * @v status            Transfer descriptor status
 * @ret rc              Error code
 *
 * Bits 2-5 of the status code provide some indication as to the root
 * cause of the error.  We incorporate these into the error code as
 * reported to usb_complete_err().
 */
#define EIO_STATUS( status ) EUNIQ ( EINFO_EIO, ( ( (status) >> 2 ) & 0xf ) )

/******************************************************************************
 *
 * Register access
 *
 ******************************************************************************
 */

/**
 * Initialise device
 *
 * @v ehci              EHCI device
 * @v regs              MMIO registers
 */
static void ehci_init ( struct ehci_device *ehci, void *regs ) {
        uint32_t hcsparams;
        uint32_t hccparams;
        size_t caplength;

        /* Locate capability and operational registers */
        ehci->cap = regs;
        caplength = readb ( ehci->cap + EHCI_CAP_CAPLENGTH );
        ehci->op = ( ehci->cap + caplength );
        DBGC2 ( ehci, "EHCI %s cap %08lx op %08lx\n", ehci->name,
                virt_to_phys ( ehci->cap ), virt_to_phys ( ehci->op ) );

        /* Read structural parameters */
        hcsparams = readl ( ehci->cap + EHCI_CAP_HCSPARAMS );
        ehci->ports = EHCI_HCSPARAMS_PORTS ( hcsparams );
        DBGC ( ehci, "EHCI %s has %d ports\n", ehci->name, ehci->ports );

        /* Read capability parameters 1 */
        hccparams = readl ( ehci->cap + EHCI_CAP_HCCPARAMS );
        ehci->addr64 = EHCI_HCCPARAMS_ADDR64 ( hccparams );
        ehci->flsize = ( EHCI_HCCPARAMS_FLSIZE ( hccparams ) ?
                         EHCI_FLSIZE_SMALL : EHCI_FLSIZE_DEFAULT );
        ehci->eecp = EHCI_HCCPARAMS_EECP ( hccparams );
        DBGC2 ( ehci, "EHCI %s %d-bit flsize %d\n", ehci->name,
                ( ehci->addr64 ? 64 : 32 ), ehci->flsize );
}

/**
 * Find extended capability
 *
 * @v ehci              EHCI device
 * @v pci               PCI device
 * @v id                Capability ID
 * @v offset            Offset to previous extended capability instance, or zero
 * @ret offset          Offset to extended capability, or zero if not found
 */
static unsigned int ehci_extended_capability ( struct ehci_device *ehci,
                                               struct pci_device *pci,
                                               unsigned int id,
                                               unsigned int offset ) {
        uint32_t eecp;

        /* Locate the extended capability */
        while ( 1 ) {

                /* Locate first or next capability as applicable */
                if ( offset ) {
                        pci_read_config_dword ( pci, offset, &eecp );
                        offset = EHCI_EECP_NEXT ( eecp );
                } else {
                        offset = ehci->eecp;
                }
                if ( ! offset )
                        return 0;

                /* Check if this is the requested capability */
                pci_read_config_dword ( pci, offset, &eecp );
                if ( EHCI_EECP_ID ( eecp ) == id )
                        return offset;
        }
}

/**
 * Calculate buffer alignment
 *
 * @v len               Length
 * @ret align           Buffer alignment
 *
 * Determine alignment required for a buffer which must be aligned to
 * at least EHCI_MIN_ALIGN and which must not cross a page boundary.
 */
static inline size_t ehci_align ( size_t len ) {
        size_t align;

        /* Align to own length (rounded up to a power of two) */
        align = ( 1 << fls ( len - 1 ) );

        /* Round up to EHCI_MIN_ALIGN if needed */
        if ( align < EHCI_MIN_ALIGN )
                align = EHCI_MIN_ALIGN;

        return align;
}

/**
 * Check control data structure reachability
 *
 * @v ehci              EHCI device
 * @v ptr               Data structure pointer
 * @ret rc              Return status code
 */
static int ehci_ctrl_reachable ( struct ehci_device *ehci, void *ptr ) {
        physaddr_t phys = virt_to_phys ( ptr );
        uint32_t segment;

        /* Always reachable in a 32-bit build */
        if ( sizeof ( physaddr_t ) <= sizeof ( uint32_t ) )
                return 0;

        /* Reachable only if control segment matches in a 64-bit build */
        segment = ( ( ( uint64_t ) phys ) >> 32 );
        if ( segment == ehci->ctrldssegment )
                return 0;

        return -ENOTSUP;
}

/******************************************************************************
 *
 * Diagnostics
 *
 ******************************************************************************
 */

/**
 * Dump host controller registers
 *
 * @v ehci              EHCI device
 */
static __unused void ehci_dump ( struct ehci_device *ehci ) {
        uint8_t caplength;
        uint16_t hciversion;
        uint32_t hcsparams;
        uint32_t hccparams;
        uint32_t usbcmd;
        uint32_t usbsts;
        uint32_t usbintr;
        uint32_t frindex;
        uint32_t ctrldssegment;
        uint32_t periodiclistbase;
        uint32_t asynclistaddr;
        uint32_t configflag;

        /* Do nothing unless debugging is enabled */
        if ( ! DBG_LOG )
                return;

        /* Dump capability registers */
        caplength = readb ( ehci->cap + EHCI_CAP_CAPLENGTH );
        hciversion = readw ( ehci->cap + EHCI_CAP_HCIVERSION );
        hcsparams = readl ( ehci->cap + EHCI_CAP_HCSPARAMS );
        hccparams = readl ( ehci->cap + EHCI_CAP_HCCPARAMS );
        DBGC ( ehci, "EHCI %s caplen %02x hciversion %04x hcsparams %08x "
               "hccparams %08x\n", ehci->name, caplength, hciversion,
               hcsparams,  hccparams );

        /* Dump operational registers */
        usbcmd = readl ( ehci->op + EHCI_OP_USBCMD );
        usbsts = readl ( ehci->op + EHCI_OP_USBSTS );
        usbintr = readl ( ehci->op + EHCI_OP_USBINTR );
        frindex = readl ( ehci->op + EHCI_OP_FRINDEX );
        ctrldssegment = readl ( ehci->op + EHCI_OP_CTRLDSSEGMENT );
        periodiclistbase = readl ( ehci->op + EHCI_OP_PERIODICLISTBASE );
        asynclistaddr = readl ( ehci->op + EHCI_OP_ASYNCLISTADDR );
        configflag = readl ( ehci->op + EHCI_OP_CONFIGFLAG );
        DBGC ( ehci, "EHCI %s usbcmd %08x usbsts %08x usbint %08x frindx "
               "%08x\n", ehci->name, usbcmd, usbsts, usbintr, frindex );
        DBGC ( ehci, "EHCI %s ctrlds %08x period %08x asyncl %08x cfgflg "
               "%08x\n", ehci->name, ctrldssegment, periodiclistbase,
               asynclistaddr, configflag );
}

/******************************************************************************
 *
 * USB legacy support
 *
 ******************************************************************************
 */

/** Prevent the release of ownership back to BIOS */
static int ehci_legacy_prevent_release;

/**
 * Initialise USB legacy support
 *
 * @v ehci              EHCI device
 * @v pci               PCI device
 */
static void ehci_legacy_init ( struct ehci_device *ehci,
                               struct pci_device *pci ) {
        unsigned int legacy;
        uint8_t bios;

        /* Locate USB legacy support capability (if present) */
        legacy = ehci_extended_capability ( ehci, pci, EHCI_EECP_ID_LEGACY, 0 );
        if ( ! legacy ) {
                /* Not an error; capability may not be present */
                DBGC ( ehci, "EHCI %s has no USB legacy support capability\n",
                       ehci->name );
                return;
        }

        /* Check if legacy USB support is enabled */
        pci_read_config_byte ( pci, ( legacy + EHCI_USBLEGSUP_BIOS ), &bios );
        if ( ! ( bios & EHCI_USBLEGSUP_BIOS_OWNED ) ) {
                /* Not an error; already owned by OS */
                DBGC ( ehci, "EHCI %s USB legacy support already disabled\n",
                       ehci->name );
                return;
        }

        /* Record presence of USB legacy support capability */
        ehci->legacy = legacy;
}

/**
 * Claim ownership from BIOS
 *
 * @v ehci              EHCI device
 * @v pci               PCI device
 */
static void ehci_legacy_claim ( struct ehci_device *ehci,
                                struct pci_device *pci ) {
        unsigned int legacy = ehci->legacy;
        uint32_t ctlsts;
        uint8_t bios;
        unsigned int i;

        /* Do nothing unless legacy support capability is present */
        if ( ! legacy )
                return;

        /* Dump original SMI usage */
        pci_read_config_dword ( pci, ( legacy + EHCI_USBLEGSUP_CTLSTS ),
                                &ctlsts );
        if ( ctlsts ) {
                DBGC ( ehci, "EHCI %s BIOS using SMIs: %08x\n",
                       ehci->name, ctlsts );
        }

        /* Claim ownership */
        pci_write_config_byte ( pci, ( legacy + EHCI_USBLEGSUP_OS ),
                                EHCI_USBLEGSUP_OS_OWNED );

        /* Wait for BIOS to release ownership */
        for ( i = 0 ; i < EHCI_USBLEGSUP_MAX_WAIT_MS ; i++ ) {

                /* Check if BIOS has released ownership */
                pci_read_config_byte ( pci, ( legacy + EHCI_USBLEGSUP_BIOS ),
                                       &bios );
                if ( ! ( bios & EHCI_USBLEGSUP_BIOS_OWNED ) ) {
                        DBGC ( ehci, "EHCI %s claimed ownership from BIOS\n",
                               ehci->name );
                        pci_read_config_dword ( pci, ( legacy +
                                                       EHCI_USBLEGSUP_CTLSTS ),
                                                &ctlsts );
                        if ( ctlsts ) {
                                DBGC ( ehci, "EHCI %s warning: BIOS retained "
                                       "SMIs: %08x\n", ehci->name, ctlsts );
                        }
                        return;
                }

                /* Delay */
                mdelay ( 1 );
        }

        /* BIOS did not release ownership.  Claim it forcibly by
         * disabling all SMIs.
         */
        DBGC ( ehci, "EHCI %s could not claim ownership from BIOS: forcibly "
               "disabling SMIs\n", ehci->name );
        pci_write_config_dword ( pci, ( legacy + EHCI_USBLEGSUP_CTLSTS ), 0 );
}

/**
 * Release ownership back to BIOS
 *
 * @v ehci              EHCI device
 * @v pci               PCI device
 */
static void ehci_legacy_release ( struct ehci_device *ehci,
                                  struct pci_device *pci ) {
        unsigned int legacy = ehci->legacy;
        uint32_t ctlsts;

        /* Do nothing unless legacy support capability is present */
        if ( ! legacy )
                return;

        /* Do nothing if releasing ownership is prevented */
        if ( ehci_legacy_prevent_release ) {
                DBGC ( ehci, "EHCI %s not releasing ownership to BIOS\n",
                       ehci->name );
                return;
        }

        /* Release ownership */
        pci_write_config_byte ( pci, ( legacy + EHCI_USBLEGSUP_OS ), 0 );
        DBGC ( ehci, "EHCI %s released ownership to BIOS\n", ehci->name );

        /* Dump restored SMI usage */
        pci_read_config_dword ( pci, ( legacy + EHCI_USBLEGSUP_CTLSTS ),
                                &ctlsts );
        DBGC ( ehci, "EHCI %s BIOS reclaimed SMIs: %08x\n",
               ehci->name, ctlsts );
}

/******************************************************************************
 *
 * Companion controllers
 *
 ******************************************************************************
 */

/**
 * Poll child companion controllers
 *
 * @v ehci              EHCI device
 */
static void ehci_poll_companions ( struct ehci_device *ehci ) {
        struct usb_bus *bus;
        struct device_description *desc;

        /* Poll any USB buses belonging to child companion controllers */
        for_each_usb_bus ( bus ) {

                /* Get underlying devices description */
                desc = &bus->dev->desc;

                /* Skip buses that are not PCI devices */
                if ( desc->bus_type != BUS_TYPE_PCI )
                        continue;

                /* Skip buses that are not part of the same PCI device */
                if ( PCI_FIRST_FUNC ( desc->location ) !=
                     PCI_FIRST_FUNC ( ehci->bus->dev->desc.location ) )
                        continue;

                /* Skip buses that are not UHCI or OHCI PCI devices */
                if ( ( desc->class != PCI_CLASS ( PCI_CLASS_SERIAL,
                                                  PCI_CLASS_SERIAL_USB,
                                                  PCI_CLASS_SERIAL_USB_UHCI ))&&
                     ( desc->class != PCI_CLASS ( PCI_CLASS_SERIAL,
                                                  PCI_CLASS_SERIAL_USB,
                                                  PCI_CLASS_SERIAL_USB_OHCI ) ))
                        continue;

                /* Poll child companion controller bus */
                DBGC2 ( ehci, "EHCI %s polling companion %s\n",
                        ehci->name, bus->name );
                usb_poll ( bus );
        }
}

/**
 * Locate EHCI companion controller
 *
 * @v pci               PCI device
 * @ret busdevfn        EHCI companion controller bus:dev.fn (if any)
 */
unsigned int ehci_companion ( struct pci_device *pci ) {
        struct pci_device tmp;
        unsigned int busdevfn;
        int rc;

        /* Look for an EHCI function on the same PCI device */
        busdevfn = pci->busdevfn;
        while ( ++busdevfn <= PCI_LAST_FUNC ( pci->busdevfn ) ) {
                pci_init ( &tmp, busdevfn );
                if ( ( rc = pci_read_config ( &tmp ) ) != 0 )
                        continue;
                if ( tmp.class == PCI_CLASS ( PCI_CLASS_SERIAL,
                                              PCI_CLASS_SERIAL_USB,
                                              PCI_CLASS_SERIAL_USB_EHCI ) )
                        return busdevfn;
        }

        return 0;
}

/******************************************************************************
 *
 * Run / stop / reset
 *
 ******************************************************************************
 */

/**
 * Start EHCI device
 *
 * @v ehci              EHCI device
 */
static void ehci_run ( struct ehci_device *ehci ) {
        uint32_t usbcmd;

        /* Set run/stop bit */
        usbcmd = readl ( ehci->op + EHCI_OP_USBCMD );
        usbcmd &= ~EHCI_USBCMD_FLSIZE_MASK;
        usbcmd |= ( EHCI_USBCMD_RUN | EHCI_USBCMD_FLSIZE ( ehci->flsize ) |
                    EHCI_USBCMD_PERIODIC | EHCI_USBCMD_ASYNC );
        writel ( usbcmd, ehci->op + EHCI_OP_USBCMD );
}

/**
 * Stop EHCI device
 *
 * @v ehci              EHCI device
 * @ret rc              Return status code
 */
static int ehci_stop ( struct ehci_device *ehci ) {
        uint32_t usbcmd;
        uint32_t usbsts;
        unsigned int i;

        /* Clear run/stop bit */
        usbcmd = readl ( ehci->op + EHCI_OP_USBCMD );
        usbcmd &= ~( EHCI_USBCMD_RUN | EHCI_USBCMD_PERIODIC |
                     EHCI_USBCMD_ASYNC );
        writel ( usbcmd, ehci->op + EHCI_OP_USBCMD );

        /* Wait for device to stop */
        for ( i = 0 ; i < EHCI_STOP_MAX_WAIT_MS ; i++ ) {

                /* Check if device is stopped */
                usbsts = readl ( ehci->op + EHCI_OP_USBSTS );
                if ( usbsts & EHCI_USBSTS_HCH )
                        return 0;

                /* Delay */
                mdelay ( 1 );
        }

        DBGC ( ehci, "EHCI %s timed out waiting for stop\n", ehci->name );
        return -ETIMEDOUT;
}

/**
 * Reset EHCI device
 *
 * @v ehci              EHCI device
 * @ret rc              Return status code
 */
static int ehci_reset ( struct ehci_device *ehci ) {
        uint32_t usbcmd;
        unsigned int i;
        int rc;

        /* The EHCI specification states that resetting a running
         * device may result in undefined behaviour, so try stopping
         * it first.
         */
        if ( ( rc = ehci_stop ( ehci ) ) != 0 ) {
                /* Ignore errors and attempt to reset the device anyway */
        }

        /* Reset device */
        writel ( EHCI_USBCMD_HCRST, ehci->op + EHCI_OP_USBCMD );

        /* Wait for reset to complete */
        for ( i = 0 ; i < EHCI_RESET_MAX_WAIT_MS ; i++ ) {

                /* Check if reset is complete */
                usbcmd = readl ( ehci->op + EHCI_OP_USBCMD );
                if ( ! ( usbcmd & EHCI_USBCMD_HCRST ) )
                        return 0;

                /* Delay */
                mdelay ( 1 );
        }

        DBGC ( ehci, "EHCI %s timed out waiting for reset\n", ehci->name );
        return -ETIMEDOUT;
}

/******************************************************************************
 *
 * Transfer descriptor rings
 *
 ******************************************************************************
 */

/**
 * Allocate transfer descriptor ring
 *
 * @v ehci              EHCI device
 * @v ring              Transfer descriptor ring
 * @ret rc              Return status code
 */
static int ehci_ring_alloc ( struct ehci_device *ehci,
                             struct ehci_ring *ring ) {
        struct ehci_transfer_descriptor *desc;
        struct ehci_transfer_descriptor *next;
        unsigned int i;
        size_t len;
        uint32_t link;
        int rc;

        /* Initialise structure */
        memset ( ring, 0, sizeof ( *ring ) );

        /* Allocate I/O buffers */
        ring->iobuf = zalloc ( EHCI_RING_COUNT * sizeof ( ring->iobuf[0] ) );
        if ( ! ring->iobuf ) {
                rc = -ENOMEM;
                goto err_alloc_iobuf;
        }

        /* Allocate queue head */
        ring->head = malloc_phys ( sizeof ( *ring->head ),
                                   ehci_align ( sizeof ( *ring->head ) ) );
        if ( ! ring->head ) {
                rc = -ENOMEM;
                goto err_alloc_queue;
        }
        if ( ( rc = ehci_ctrl_reachable ( ehci, ring->head ) ) != 0 ) {
                DBGC ( ehci, "EHCI %s queue head unreachable\n", ehci->name );
                goto err_unreachable_queue;
        }
        memset ( ring->head, 0, sizeof ( *ring->head ) );

        /* Allocate transfer descriptors */
        len = ( EHCI_RING_COUNT * sizeof ( ring->desc[0] ) );
        ring->desc = malloc_phys ( len, sizeof ( ring->desc[0] ) );
        if ( ! ring->desc ) {
                rc = -ENOMEM;
                goto err_alloc_desc;
        }
        memset ( ring->desc, 0, len );

        /* Initialise transfer descriptors */
        for ( i = 0 ; i < EHCI_RING_COUNT ; i++ ) {
                desc = &ring->desc[i];
                if ( ( rc = ehci_ctrl_reachable ( ehci, desc ) ) != 0 ) {
                        DBGC ( ehci, "EHCI %s descriptor unreachable\n",
                               ehci->name );
                        goto err_unreachable_desc;
                }
                next = &ring->desc[ ( i + 1 ) % EHCI_RING_COUNT ];
                link = virt_to_phys ( next );
                desc->next = cpu_to_le32 ( link );
                desc->alt = cpu_to_le32 ( link );
        }

        /* Initialise queue head */
        link = virt_to_phys ( &ring->desc[0] );
        ring->head->cache.next = cpu_to_le32 ( link );

        return 0;

 err_unreachable_desc:
        free_phys ( ring->desc, len );
 err_alloc_desc:
 err_unreachable_queue:
        free_phys ( ring->head, sizeof ( *ring->head ) );
 err_alloc_queue:
        free ( ring->iobuf );
 err_alloc_iobuf:
        return rc;
}

/**
 * Free transfer descriptor ring
 *
 * @v ring              Transfer descriptor ring
 */
static void ehci_ring_free ( struct ehci_ring *ring ) {
        unsigned int i;

        /* Sanity checks */
        assert ( ehci_ring_fill ( ring ) == 0 );
        for ( i = 0 ; i < EHCI_RING_COUNT ; i++ )
                assert ( ring->iobuf[i] == NULL );

        /* Free transfer descriptors */
        free_phys ( ring->desc, ( EHCI_RING_COUNT *
                                  sizeof ( ring->desc[0] ) ) );

        /* Free queue head */
        free_phys ( ring->head, sizeof ( *ring->head ) );

        /* Free I/O buffers */
        free ( ring->iobuf );
}

/**
 * Enqueue transfer descriptors
 *
 * @v ehci              EHCI device
 * @v ring              Transfer descriptor ring
 * @v iobuf             I/O buffer
 * @v xfers             Transfers
 * @v count             Number of transfers
 * @ret rc              Return status code
 */
static int ehci_enqueue ( struct ehci_device *ehci, struct ehci_ring *ring,
                          struct io_buffer *iobuf,
                          const struct ehci_transfer *xfer,
                          unsigned int count ) {
        struct ehci_transfer_descriptor *desc;
        physaddr_t phys;
        void *data;
        size_t len;
        size_t offset;
        size_t frag_len;
        unsigned int toggle;
        unsigned int index;
        unsigned int i;

        /* Sanity check */
        assert ( iobuf != NULL );
        assert ( count > 0 );

        /* Fail if ring does not have sufficient space */
        if ( ehci_ring_remaining ( ring ) < count )
                return -ENOBUFS;

        /* Fail if any portion is unreachable */
        for ( i = 0 ; i < count ; i++ ) {
                if ( ! xfer[i].len )
                        continue;
                phys = ( virt_to_phys ( xfer[i].data ) + xfer[i].len - 1 );
                if ( ( phys > 0xffffffffUL ) && ( ! ehci->addr64 ) )
                        return -ENOTSUP;
        }

        /* Enqueue each transfer, recording the I/O buffer with the last */
        for ( ; count ; ring->prod++, xfer++ ) {

                /* Populate descriptor header */
                index = ( ring->prod % EHCI_RING_COUNT );
                desc = &ring->desc[index];
                toggle = ( xfer->flags & EHCI_FL_TOGGLE );
                assert ( xfer->len <= EHCI_LEN_MASK );
                assert ( EHCI_FL_TOGGLE == EHCI_LEN_TOGGLE );
                desc->len = cpu_to_le16 ( xfer->len | toggle );
                desc->flags = ( xfer->flags | EHCI_FL_CERR_MAX );

                /* Populate buffer pointers */
                data = xfer->data;
                len = xfer->len;
                for ( i = 0 ; len ; i++ ) {

                        /* Calculate length of this fragment */
                        phys = virt_to_phys ( data );
                        offset = ( phys & ( EHCI_PAGE_ALIGN - 1 ) );
                        frag_len = ( EHCI_PAGE_ALIGN - offset );
                        if ( frag_len > len )
                                frag_len = len;

                        /* Sanity checks */
                        assert ( ( i == 0 ) || ( offset == 0 ) );
                        assert ( i < ( sizeof ( desc->low ) /
                                       sizeof ( desc->low[0] ) ) );

                        /* Populate buffer pointer */
                        desc->low[i] = cpu_to_le32 ( phys );
                        if ( sizeof ( physaddr_t ) > sizeof ( uint32_t ) ) {
                                desc->high[i] =
                                        cpu_to_le32 ( ((uint64_t) phys) >> 32 );
                        }

                        /* Move to next fragment */
                        data += frag_len;
                        len -= frag_len;
                }

                /* Ensure everything is valid before activating descriptor */
                wmb();
                desc->status = EHCI_STATUS_ACTIVE;

                /* Record I/O buffer against last ring index */
                if ( --count == 0 )
                        ring->iobuf[index] = iobuf;
        }

        return 0;
}

/**
 * Dequeue a transfer descriptor
 *
 * @v ring              Transfer descriptor ring
 * @ret iobuf           I/O buffer (or NULL)
 */
static struct io_buffer * ehci_dequeue ( struct ehci_ring *ring ) {
        struct ehci_transfer_descriptor *desc;
        struct io_buffer *iobuf;
        unsigned int index = ( ring->cons % EHCI_RING_COUNT );

        /* Sanity check */
        assert ( ehci_ring_fill ( ring ) > 0 );

        /* Mark descriptor as inactive (and not halted) */
        desc = &ring->desc[index];
        desc->status = 0;

        /* Retrieve I/O buffer */
        iobuf = ring->iobuf[index];
        ring->iobuf[index] = NULL;

        /* Update consumer counter */
        ring->cons++;

        return iobuf;
}

/******************************************************************************
 *
 * Schedule management
 *
 ******************************************************************************
 */

/**
 * Get link value for a queue head
 *
 * @v queue             Queue head
 * @ret link            Link value
 */
static inline uint32_t ehci_link_qh ( struct ehci_queue_head *queue ) {

        return ( virt_to_phys ( queue ) | EHCI_LINK_TYPE_QH );
}

/**
 * (Re)build asynchronous schedule
 *
 * @v ehci              EHCI device
 */
static void ehci_async_schedule ( struct ehci_device *ehci ) {
        struct ehci_endpoint *endpoint;
        struct ehci_queue_head *queue;
        uint32_t link;

        /* Build schedule in reverse order of execution.  Provided
         * that we only ever add or remove single endpoints, this can
         * safely run concurrently with hardware execution of the
         * schedule.
         */
        link = ehci_link_qh ( ehci->head );
        list_for_each_entry_reverse ( endpoint, &ehci->async, schedule ) {
                queue = endpoint->ring.head;
                queue->link = cpu_to_le32 ( link );
                wmb();
                link = ehci_link_qh ( queue );
        }
        ehci->head->link = cpu_to_le32 ( link );
        wmb();
}

/**
 * Add endpoint to asynchronous schedule
 *
 * @v endpoint          Endpoint
 */
static void ehci_async_add ( struct ehci_endpoint *endpoint ) {
        struct ehci_device *ehci = endpoint->ehci;

        /* Add to end of schedule */
        list_add_tail ( &endpoint->schedule, &ehci->async );

        /* Rebuild schedule */
        ehci_async_schedule ( ehci );
}

/**
 * Remove endpoint from asynchronous schedule
 *
 * @v endpoint          Endpoint
 * @ret rc              Return status code
 */
static int ehci_async_del ( struct ehci_endpoint *endpoint ) {
        struct ehci_device *ehci = endpoint->ehci;
        uint32_t usbcmd;
        uint32_t usbsts;
        unsigned int i;

        /* Remove from schedule */
        list_check_contains_entry ( endpoint, &ehci->async, schedule );
        list_del ( &endpoint->schedule );

        /* Rebuild schedule */
        ehci_async_schedule ( ehci );

        /* Request notification when asynchronous schedule advances */
        usbcmd = readl ( ehci->op + EHCI_OP_USBCMD );
        usbcmd |= EHCI_USBCMD_ASYNC_ADVANCE;
        writel ( usbcmd, ehci->op + EHCI_OP_USBCMD );

        /* Wait for asynchronous schedule to advance */
        for ( i = 0 ; i < EHCI_ASYNC_ADVANCE_MAX_WAIT_MS ; i++ ) {

                /* Check for asynchronous schedule advancing */
                usbsts = readl ( ehci->op + EHCI_OP_USBSTS );
                if ( usbsts & EHCI_USBSTS_ASYNC_ADVANCE ) {
                        usbsts &= ~EHCI_USBSTS_CHANGE;
                        usbsts |= EHCI_USBSTS_ASYNC_ADVANCE;
                        writel ( usbsts, ehci->op + EHCI_OP_USBSTS );
                        return 0;
                }

                /* Delay */
                mdelay ( 1 );
        }

        /* Bad things will probably happen now */
        DBGC ( ehci, "EHCI %s timed out waiting for asynchronous schedule "
               "to advance\n", ehci->name );
        return -ETIMEDOUT;
}

/**
 * (Re)build periodic schedule
 *
 * @v ehci              EHCI device
 */
static void ehci_periodic_schedule ( struct ehci_device *ehci ) {
        struct ehci_endpoint *endpoint;
        struct ehci_queue_head *queue;
        uint32_t link;
        unsigned int frames;
        unsigned int max_interval;
        unsigned int i;

        /* Build schedule in reverse order of execution.  Provided
         * that we only ever add or remove single endpoints, this can
         * safely run concurrently with hardware execution of the
         * schedule.
         */
        DBGCP ( ehci, "EHCI %s periodic schedule: ", ehci->name );
        link = EHCI_LINK_TERMINATE;
        list_for_each_entry_reverse ( endpoint, &ehci->periodic, schedule ) {
                queue = endpoint->ring.head;
                queue->link = cpu_to_le32 ( link );
                wmb();
                DBGCP ( ehci, "%s%d",
                        ( ( link == EHCI_LINK_TERMINATE ) ? "" : "<-" ),
                        endpoint->ep->interval );
                link = ehci_link_qh ( queue );
        }
        DBGCP ( ehci, "\n" );

        /* Populate periodic frame list */
        DBGCP ( ehci, "EHCI %s periodic frame list:", ehci->name );
        frames = EHCI_PERIODIC_FRAMES ( ehci->flsize );
        for ( i = 0 ; i < frames ; i++ ) {

                /* Calculate maximum interval (in microframes) which
                 * may appear as part of this frame list.
                 */
                if ( i == 0 ) {
                        /* Start of list: include all endpoints */
                        max_interval = -1U;
                } else {
                        /* Calculate highest power-of-two frame interval */
                        max_interval = ( 1 << ( ffs ( i ) - 1 ) );
                        /* Convert to microframes */
                        max_interval <<= 3;
                        /* Round up to nearest 2^n-1 */
                        max_interval = ( ( max_interval << 1 ) - 1 );
                }

                /* Find first endpoint in schedule satisfying this
                 * maximum interval constraint.
                 */
                link = EHCI_LINK_TERMINATE;
                list_for_each_entry ( endpoint, &ehci->periodic, schedule ) {
                        if ( endpoint->ep->interval <= max_interval ) {
                                queue = endpoint->ring.head;
                                link = ehci_link_qh ( queue );
                                DBGCP ( ehci, " %d:%d",
                                        i, endpoint->ep->interval );
                                break;
                        }
                }
                ehci->frame[i].link = cpu_to_le32 ( link );
        }
        wmb();
        DBGCP ( ehci, "\n" );
}

/**
 * Add endpoint to periodic schedule
 *
 * @v endpoint          Endpoint
 */
static void ehci_periodic_add ( struct ehci_endpoint *endpoint ) {
        struct ehci_device *ehci = endpoint->ehci;
        struct ehci_endpoint *before;
        unsigned int interval = endpoint->ep->interval;

        /* Find first endpoint with a smaller interval */
        list_for_each_entry ( before, &ehci->periodic, schedule ) {
                if ( before->ep->interval < interval )
                        break;
        }
        list_add_tail ( &endpoint->schedule, &before->schedule );

        /* Rebuild schedule */
        ehci_periodic_schedule ( ehci );
}

/**
 * Remove endpoint from periodic schedule
 *
 * @v endpoint          Endpoint
 * @ret rc              Return status code
 */
static int ehci_periodic_del ( struct ehci_endpoint *endpoint ) {
        struct ehci_device *ehci = endpoint->ehci;

        /* Remove from schedule */
        list_check_contains_entry ( endpoint, &ehci->periodic, schedule );
        list_del ( &endpoint->schedule );

        /* Rebuild schedule */
        ehci_periodic_schedule ( ehci );

        /* Delay for a whole USB frame (with a 100% safety margin) */
        mdelay ( 2 );

        return 0;
}

/**
 * Add endpoint to appropriate schedule
 *
 * @v endpoint          Endpoint
 */
static void ehci_schedule_add ( struct ehci_endpoint *endpoint ) {
        struct usb_endpoint *ep = endpoint->ep;
        unsigned int attr = ( ep->attributes & USB_ENDPOINT_ATTR_TYPE_MASK );

        if ( attr == USB_ENDPOINT_ATTR_INTERRUPT ) {
                ehci_periodic_add ( endpoint );
        } else {
                ehci_async_add ( endpoint );
        }
}

/**
 * Remove endpoint from appropriate schedule
 *
 * @v endpoint          Endpoint
 * @ret rc              Return status code
 */
static int ehci_schedule_del ( struct ehci_endpoint *endpoint ) {
        struct usb_endpoint *ep = endpoint->ep;
        unsigned int attr = ( ep->attributes & USB_ENDPOINT_ATTR_TYPE_MASK );

        if ( attr == USB_ENDPOINT_ATTR_INTERRUPT ) {
                return ehci_periodic_del ( endpoint );
        } else {
                return ehci_async_del ( endpoint );
        }
}

/******************************************************************************
 *
 * Endpoint operations
 *
 ******************************************************************************
 */

/**
 * Determine endpoint characteristics
 *
 * @v ep                USB endpoint
 * @ret chr             Endpoint characteristics
 */
static uint32_t ehci_endpoint_characteristics ( struct usb_endpoint *ep ) {
        struct usb_device *usb = ep->usb;
        unsigned int attr = ( ep->attributes & USB_ENDPOINT_ATTR_TYPE_MASK );
        uint32_t chr;

        /* Determine basic characteristics */
        chr = ( EHCI_CHR_ADDRESS ( usb->address ) |
                EHCI_CHR_ENDPOINT ( ep->address ) |
                EHCI_CHR_MAX_LEN ( ep->mtu ) );

        /* Control endpoints require manual control of the data toggle */
        if ( attr == USB_ENDPOINT_ATTR_CONTROL )
                chr |= EHCI_CHR_TOGGLE;

        /* Determine endpoint speed */
        if ( usb->speed == USB_SPEED_HIGH ) {
                chr |= EHCI_CHR_EPS_HIGH;
        } else {
                if ( usb->speed == USB_SPEED_FULL ) {
                        chr |= EHCI_CHR_EPS_FULL;
                } else {
                        chr |= EHCI_CHR_EPS_LOW;
                }
                if ( attr == USB_ENDPOINT_ATTR_CONTROL )
                        chr |= EHCI_CHR_CONTROL;
        }

        return chr;
}

/**
 * Determine endpoint capabilities
 *
 * @v ep                USB endpoint
 * @ret cap             Endpoint capabilities
 */
static uint32_t ehci_endpoint_capabilities ( struct usb_endpoint *ep ) {
        struct usb_device *usb = ep->usb;
        struct usb_port *tt = usb_transaction_translator ( usb );
        unsigned int attr = ( ep->attributes & USB_ENDPOINT_ATTR_TYPE_MASK );
        uint32_t cap;
        unsigned int i;

        /* Determine basic capabilities */
        cap = EHCI_CAP_MULT ( ep->burst + 1 );

        /* Determine interrupt schedule mask, if applicable */
        if ( ( attr == USB_ENDPOINT_ATTR_INTERRUPT ) &&
             ( ( ep->interval != 0 ) /* avoid infinite loop */ ) ) {
                for ( i = 0 ; i < 8 /* microframes per frame */ ;
                      i += ep->interval ) {
                        cap |= EHCI_CAP_INTR_SCHED ( i );
                }
        }

        /* Set transaction translator hub address and port, if applicable */
        if ( tt ) {
                assert ( tt->hub->usb );
                cap |= ( EHCI_CAP_TT_HUB ( tt->hub->usb->address ) |
                         EHCI_CAP_TT_PORT ( tt->address ) );
                if ( attr == USB_ENDPOINT_ATTR_INTERRUPT )
                        cap |= EHCI_CAP_SPLIT_SCHED_DEFAULT;
        }

        return cap;
}

/**
 * Update endpoint characteristics and capabilities
 *
 * @v ep                USB endpoint
 */
static void ehci_endpoint_update ( struct usb_endpoint *ep ) {
        struct ehci_endpoint *endpoint = usb_endpoint_get_hostdata ( ep );
        struct ehci_queue_head *head;

        /* Update queue characteristics and capabilities */
        head = endpoint->ring.head;
        head->chr = cpu_to_le32 ( ehci_endpoint_characteristics ( ep ) );
        head->cap = cpu_to_le32 ( ehci_endpoint_capabilities ( ep ) );
}

/**
 * Open endpoint
 *
 * @v ep                USB endpoint
 * @ret rc              Return status code
 */
static int ehci_endpoint_open ( struct usb_endpoint *ep ) {
        struct usb_device *usb = ep->usb;
        struct ehci_device *ehci = usb_get_hostdata ( usb );
        struct ehci_endpoint *endpoint;
        int rc;

        /* Allocate and initialise structure */
        endpoint = zalloc ( sizeof ( *endpoint ) );
        if ( ! endpoint ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        endpoint->ehci = ehci;
        endpoint->ep = ep;
        usb_endpoint_set_hostdata ( ep, endpoint );

        /* Initialise descriptor ring */
        if ( ( rc = ehci_ring_alloc ( ehci, &endpoint->ring ) ) != 0 )
                goto err_ring_alloc;

        /* Update queue characteristics and capabilities */
        ehci_endpoint_update ( ep );

        /* Add to list of endpoints */
        list_add_tail ( &endpoint->list, &ehci->endpoints );

        /* Add to schedule */
        ehci_schedule_add ( endpoint );

        return 0;

        ehci_ring_free ( &endpoint->ring );
 err_ring_alloc:
        free ( endpoint );
 err_alloc:
        return rc;
}

/**
 * Close endpoint
 *
 * @v ep                USB endpoint
 */
static void ehci_endpoint_close ( struct usb_endpoint *ep ) {
        struct ehci_endpoint *endpoint = usb_endpoint_get_hostdata ( ep );
        struct ehci_device *ehci = endpoint->ehci;
        struct usb_device *usb = ep->usb;
        struct io_buffer *iobuf;
        int rc;

        /* Remove from schedule */
        if ( ( rc = ehci_schedule_del ( endpoint ) ) != 0 ) {
                /* No way to prevent hardware from continuing to
                 * access the memory, so leak it.
                 */
                DBGC ( ehci, "EHCI %s %s could not unschedule: %s\n",
                       usb->name, usb_endpoint_name ( ep ), strerror ( rc ) );
                return;
        }

        /* Cancel any incomplete transfers */
        while ( ehci_ring_fill ( &endpoint->ring ) ) {
                iobuf = ehci_dequeue ( &endpoint->ring );
                if ( iobuf )
                        usb_complete_err ( ep, iobuf, -ECANCELED );
        }

        /* Remove from list of endpoints */
        list_del ( &endpoint->list );

        /* Free descriptor ring */
        ehci_ring_free ( &endpoint->ring );

        /* Free endpoint */
        free ( endpoint );
}

/**
 * Reset endpoint
 *
 * @v ep                USB endpoint
 * @ret rc              Return status code
 */
static int ehci_endpoint_reset ( struct usb_endpoint *ep ) {
        struct ehci_endpoint *endpoint = usb_endpoint_get_hostdata ( ep );
        struct ehci_ring *ring = &endpoint->ring;
        struct ehci_transfer_descriptor *cache = &ring->head->cache;
        uint32_t link;

        /* Sanity checks */
        assert ( ! ( cache->status & EHCI_STATUS_ACTIVE ) );
        assert ( cache->status & EHCI_STATUS_HALTED );

        /* Reset residual count */
        ring->residual = 0;

        /* Reset data toggle */
        cache->len = 0;

        /* Prepare to restart at next unconsumed descriptor */
        link = virt_to_phys ( &ring->desc[ ring->cons % EHCI_RING_COUNT ] );
        cache->next = cpu_to_le32 ( link );

        /* Restart ring */
        wmb();
        cache->status = 0;

        return 0;
}

/**
 * Update MTU
 *
 * @v ep                USB endpoint
 * @ret rc              Return status code
 */
static int ehci_endpoint_mtu ( struct usb_endpoint *ep ) {

        /* Update endpoint characteristics and capabilities */
        ehci_endpoint_update ( ep );

        return 0;
}

/**
 * Enqueue message transfer
 *
 * @v ep                USB endpoint
 * @v iobuf             I/O buffer
 * @ret rc              Return status code
 */
static int ehci_endpoint_message ( struct usb_endpoint *ep,
                                   struct io_buffer *iobuf ) {
        struct ehci_endpoint *endpoint = usb_endpoint_get_hostdata ( ep );
        struct ehci_device *ehci = endpoint->ehci;
        struct usb_setup_packet *packet;
        unsigned int input;
        struct ehci_transfer xfers[3];
        struct ehci_transfer *xfer = xfers;
        size_t len;
        int rc;

        /* Construct setup stage */
        assert ( iob_len ( iobuf ) >= sizeof ( *packet ) );
        packet = iobuf->data;
        iob_pull ( iobuf, sizeof ( *packet ) );
        xfer->data = packet;
        xfer->len = sizeof ( *packet );
        xfer->flags = EHCI_FL_PID_SETUP;
        xfer++;

        /* Construct data stage, if applicable */
        len = iob_len ( iobuf );
        input = ( packet->request & cpu_to_le16 ( USB_DIR_IN ) );
        if ( len ) {
                xfer->data = iobuf->data;
                xfer->len = len;
                xfer->flags = ( EHCI_FL_TOGGLE |
                                ( input ? EHCI_FL_PID_IN : EHCI_FL_PID_OUT ) );
                xfer++;
        }

        /* Construct status stage */
        xfer->data = NULL;
        xfer->len = 0;
        xfer->flags = ( EHCI_FL_TOGGLE | EHCI_FL_IOC |
                        ( ( len && input ) ? EHCI_FL_PID_OUT : EHCI_FL_PID_IN));
        xfer++;

        /* Enqueue transfer */
        if ( ( rc = ehci_enqueue ( ehci, &endpoint->ring, iobuf, xfers,
                                   ( xfer - xfers ) ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Calculate number of transfer descriptors
 *
 * @v len               Length of data
 * @v zlp               Append a zero-length packet
 * @ret count           Number of transfer descriptors
 */
static unsigned int ehci_endpoint_count ( size_t len, int zlp ) {
        unsigned int count;

        /* Split into 16kB transfers.  A single transfer can handle up
         * to 20kB if it happens to be page-aligned, or up to 16kB
         * with arbitrary alignment.  We simplify the code by assuming
         * that we can fit only 16kB into each transfer.
         */
        count = ( ( len + EHCI_MTU - 1 ) / EHCI_MTU );

        /* Append a zero-length transfer if applicable */
        if ( zlp || ( count == 0 ) )
                count++;

        return count;
}

/**
 * Enqueue stream transfer
 *
 * @v ep                USB endpoint
 * @v iobuf             I/O buffer
 * @v zlp               Append a zero-length packet
 * @ret rc              Return status code
 */
static int ehci_endpoint_stream ( struct usb_endpoint *ep,
                                  struct io_buffer *iobuf, int zlp ) {
        struct ehci_endpoint *endpoint = usb_endpoint_get_hostdata ( ep );
        struct ehci_device *ehci = endpoint->ehci;
        void *data = iobuf->data;
        size_t len = iob_len ( iobuf );
        unsigned int count = ehci_endpoint_count ( len, zlp );
        unsigned int input = ( ep->address & USB_DIR_IN );
        unsigned int flags = ( input ? EHCI_FL_PID_IN : EHCI_FL_PID_OUT );
        struct ehci_transfer xfers[count];
        struct ehci_transfer *xfer = xfers;
        size_t xfer_len;
        unsigned int i;
        int rc;

        /* Create transfers */
        for ( i = 0 ; i < count ; i++ ) {

                /* Calculate transfer length */
                xfer_len = EHCI_MTU;
                if ( xfer_len > len )
                        xfer_len = len;

                /* Create transfer */
                xfer->data = data;
                xfer->len = xfer_len;
                xfer->flags = flags;

                /* Move to next transfer */
                data += xfer_len;
                len -= xfer_len;
                xfer++;
        }
        xfer[-1].flags |= EHCI_FL_IOC;

        /* Enqueue transfer */
        if ( ( rc = ehci_enqueue ( ehci, &endpoint->ring, iobuf, xfers,
                                   count ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Poll for completions
 *
 * @v endpoint          Endpoint
 */
static void ehci_endpoint_poll ( struct ehci_endpoint *endpoint ) {
        struct ehci_device *ehci = endpoint->ehci;
        struct ehci_ring *ring = &endpoint->ring;
        struct ehci_transfer_descriptor *desc;
        struct usb_endpoint *ep = endpoint->ep;
        struct usb_device *usb = ep->usb;
        struct io_buffer *iobuf;
        unsigned int index;
        unsigned int status;
        int rc;

        /* Consume all completed descriptors */
        while ( ehci_ring_fill ( &endpoint->ring ) ) {

                /* Stop if we reach an uncompleted descriptor */
                rmb();
                index = ( ring->cons % EHCI_RING_COUNT );
                desc = &ring->desc[index];
                status = desc->status;
                if ( status & EHCI_STATUS_ACTIVE )
                        break;

                /* Consume this descriptor */
                iobuf = ehci_dequeue ( ring );

                /* If we have encountered an error, then consume all
                 * remaining descriptors in this transaction, report
                 * the error to the USB core, and stop further
                 * processing.
                 */
                if ( status & EHCI_STATUS_HALTED ) {
                        rc = -EIO_STATUS ( status );
                        DBGC ( ehci, "EHCI %s %s completion %d failed (status "
                               "%02x): %s\n", usb->name,
                               usb_endpoint_name ( ep ), index, status,
                               strerror ( rc ) );
                        while ( ! iobuf )
                                iobuf = ehci_dequeue ( ring );
                        usb_complete_err ( endpoint->ep, iobuf, rc );
                        return;
                }

                /* Accumulate residual data count */
                ring->residual += ( le16_to_cpu ( desc->len ) & EHCI_LEN_MASK );

                /* If this is not the end of a transaction (i.e. has
                 * no I/O buffer), then continue to next descriptor.
                 */
                if ( ! iobuf )
                        continue;

                /* Update I/O buffer length */
                iob_unput ( iobuf, ring->residual );
                ring->residual = 0;

                /* Report completion to USB core */
                usb_complete ( endpoint->ep, iobuf );
        }
}

/******************************************************************************
 *
 * Device operations
 *
 ******************************************************************************
 */

/**
 * Open device
 *
 * @v usb               USB device
 * @ret rc              Return status code
 */
static int ehci_device_open ( struct usb_device *usb ) {
        struct ehci_device *ehci = usb_bus_get_hostdata ( usb->port->hub->bus );

        usb_set_hostdata ( usb, ehci );
        return 0;
}

/**
 * Close device
 *
 * @v usb               USB device
 */
static void ehci_device_close ( struct usb_device *usb ) {
        struct ehci_device *ehci = usb_get_hostdata ( usb );
        struct usb_bus *bus = ehci->bus;

        /* Free device address, if assigned */
        if ( usb->address )
                usb_free_address ( bus, usb->address );
}

/**
 * Assign device address
 *
 * @v usb               USB device
 * @ret rc              Return status code
 */
static int ehci_device_address ( struct usb_device *usb ) {
        struct ehci_device *ehci = usb_get_hostdata ( usb );
        struct usb_bus *bus = ehci->bus;
        struct usb_endpoint *ep0 = usb_endpoint ( usb, USB_EP0_ADDRESS );
        int address;
        int rc;

        /* Sanity checks */
        assert ( usb->address == 0 );
        assert ( ep0 != NULL );

        /* Allocate device address */
        address = usb_alloc_address ( bus );
        if ( address < 0 ) {
                rc = address;
                DBGC ( ehci, "EHCI %s could not allocate address: %s\n",
                       usb->name, strerror ( rc ) );
                goto err_alloc_address;
        }

        /* Set address */
        if ( ( rc = usb_set_address ( usb, address ) ) != 0 )
                goto err_set_address;

        /* Update device address */
        usb->address = address;

        /* Update control endpoint characteristics and capabilities */
        ehci_endpoint_update ( ep0 );

        return 0;

 err_set_address:
        usb_free_address ( bus, address );
 err_alloc_address:
        return rc;
}

/******************************************************************************
 *
 * Hub operations
 *
 ******************************************************************************
 */

/**
 * Open hub
 *
 * @v hub               USB hub
 * @ret rc              Return status code
 */
static int ehci_hub_open ( struct usb_hub *hub __unused ) {

        /* Nothing to do */
        return 0;
}

/**
 * Close hub
 *
 * @v hub               USB hub
 */
static void ehci_hub_close ( struct usb_hub *hub __unused ) {

        /* Nothing to do */
}

/******************************************************************************
 *
 * Root hub operations
 *
 ******************************************************************************
 */

/**
 * Open root hub
 *
 * @v hub               USB hub
 * @ret rc              Return status code
 */
static int ehci_root_open ( struct usb_hub *hub ) {
        struct ehci_device *ehci = usb_hub_get_drvdata ( hub );
        uint32_t portsc;
        unsigned int i;

        /* Route all ports to EHCI controller */
        writel ( EHCI_CONFIGFLAG_CF, ehci->op + EHCI_OP_CONFIGFLAG );

        /* Enable power to all ports */
        for ( i = 1 ; i <= ehci->ports ; i++ ) {
                portsc = readl ( ehci->op + EHCI_OP_PORTSC ( i ) );
                portsc &= ~EHCI_PORTSC_CHANGE;
                portsc |= EHCI_PORTSC_PP;
                writel ( portsc, ehci->op + EHCI_OP_PORTSC ( i ) );
        }

        /* Wait 20ms after potentially enabling power to a port */
        mdelay ( EHCI_PORT_POWER_DELAY_MS );

        return 0;
}

/**
 * Close root hub
 *
 * @v hub               USB hub
 */
static void ehci_root_close ( struct usb_hub *hub ) {
        struct ehci_device *ehci = usb_hub_get_drvdata ( hub );

        /* Route all ports back to companion controllers */
        writel ( 0, ehci->op + EHCI_OP_CONFIGFLAG );
}

/**
 * Enable port
 *
 * @v hub               USB hub
 * @v port              USB port
 * @ret rc              Return status code
 */
static int ehci_root_enable ( struct usb_hub *hub, struct usb_port *port ) {
        struct ehci_device *ehci = usb_hub_get_drvdata ( hub );
        uint32_t portsc;
        unsigned int line;
        unsigned int i;

        /* Check for a low-speed device */
        portsc = readl ( ehci->op + EHCI_OP_PORTSC ( port->address ) );
        line = EHCI_PORTSC_LINE_STATUS ( portsc );
        if ( line == EHCI_PORTSC_LINE_STATUS_LOW ) {
                DBGC ( ehci, "EHCI %s-%d detected low-speed device: "
                       "disowning\n", ehci->name, port->address );
                goto disown;
        }

        /* Reset port */
        portsc &= ~( EHCI_PORTSC_PED | EHCI_PORTSC_CHANGE );
        portsc |= EHCI_PORTSC_PR;
        writel ( portsc, ehci->op + EHCI_OP_PORTSC ( port->address ) );
        mdelay ( USB_RESET_DELAY_MS );
        portsc &= ~EHCI_PORTSC_PR;
        writel ( portsc, ehci->op + EHCI_OP_PORTSC ( port->address ) );

        /* Wait for reset to complete */
        for ( i = 0 ; i < EHCI_PORT_RESET_MAX_WAIT_MS ; i++ ) {

                /* Check port status */
                portsc = readl ( ehci->op + EHCI_OP_PORTSC ( port->address ) );
                if ( ! ( portsc & EHCI_PORTSC_PR ) ) {
                        if ( portsc & EHCI_PORTSC_PED )
                                return 0;
                        DBGC ( ehci, "EHCI %s-%d not enabled after reset: "
                               "disowning\n", ehci->name, port->address );
                        goto disown;
                }

                /* Delay */
                mdelay ( 1 );
        }

        DBGC ( ehci, "EHCI %s-%d timed out waiting for port to reset\n",
               ehci->name, port->address );
        return -ETIMEDOUT;

 disown:
        /* Disown port */
        portsc &= ~EHCI_PORTSC_CHANGE;
        portsc |= EHCI_PORTSC_OWNER;
        writel ( portsc, ehci->op + EHCI_OP_PORTSC ( port->address ) );

        /* Delay to allow child companion controllers to settle */
        mdelay ( EHCI_DISOWN_DELAY_MS );

        /* Poll child companion controllers */
        ehci_poll_companions ( ehci );

        return -ENODEV;
}

/**
 * Disable port
 *
 * @v hub               USB hub
 * @v port              USB port
 * @ret rc              Return status code
 */
static int ehci_root_disable ( struct usb_hub *hub, struct usb_port *port ) {
        struct ehci_device *ehci = usb_hub_get_drvdata ( hub );
        uint32_t portsc;

        /* Disable port */
        portsc = readl ( ehci->op + EHCI_OP_PORTSC ( port->address ) );
        portsc &= ~( EHCI_PORTSC_PED | EHCI_PORTSC_CHANGE );
        writel ( portsc, ehci->op + EHCI_OP_PORTSC ( port->address ) );

        return 0;
}

/**
 * Update root hub port speed
 *
 * @v hub               USB hub
 * @v port              USB port
 * @ret rc              Return status code
 */
static int ehci_root_speed ( struct usb_hub *hub, struct usb_port *port ) {
        struct ehci_device *ehci = usb_hub_get_drvdata ( hub );
        uint32_t portsc;
        unsigned int speed;
        unsigned int line;
        int ccs;
        int csc;
        int ped;

        /* Read port status */
        portsc = readl ( ehci->op + EHCI_OP_PORTSC ( port->address ) );
        DBGC2 ( ehci, "EHCI %s-%d status is %08x\n",
                ehci->name, port->address, portsc );
        ccs = ( portsc & EHCI_PORTSC_CCS );
        csc = ( portsc & EHCI_PORTSC_CSC );
        ped = ( portsc & EHCI_PORTSC_PED );
        line = EHCI_PORTSC_LINE_STATUS ( portsc );

        /* Record disconnections and clear changes */
        port->disconnected |= csc;
        writel ( portsc, ehci->op + EHCI_OP_PORTSC ( port->address ) );

        /* Determine port speed */
        if ( ! ccs ) {
                /* Port not connected */
                speed = USB_SPEED_NONE;
        } else if ( line == EHCI_PORTSC_LINE_STATUS_LOW ) {
                /* Detected as low-speed */
                speed = USB_SPEED_LOW;
        } else if ( ped ) {
                /* Port already enabled: must be high-speed */
                speed = USB_SPEED_HIGH;
        } else {
                /* Not low-speed and not yet enabled.  Could be either
                 * full-speed or high-speed; we can't yet tell.
                 */
                speed = USB_SPEED_FULL;
        }
        port->speed = speed;
        return 0;
}

/**
 * Clear transaction translator buffer
 *
 * @v hub               USB hub
 * @v port              USB port
 * @v ep                USB endpoint
 * @ret rc              Return status code
 */
static int ehci_root_clear_tt ( struct usb_hub *hub, struct usb_port *port,
                                struct usb_endpoint *ep ) {
        struct ehci_device *ehci = usb_hub_get_drvdata ( hub );

        /* Should never be called; this is a root hub */
        DBGC ( ehci, "EHCI %s-%d nonsensical CLEAR_TT for %s %s\n", ehci->name,
               port->address, ep->usb->name, usb_endpoint_name ( ep ) );

        return -ENOTSUP;
}

/**
 * Poll for port status changes
 *
 * @v hub               USB hub
 * @v port              USB port
 */
static void ehci_root_poll ( struct usb_hub *hub, struct usb_port *port ) {
        struct ehci_device *ehci = usb_hub_get_drvdata ( hub );
        uint32_t portsc;
        uint32_t change;

        /* Do nothing unless something has changed */
        portsc = readl ( ehci->op + EHCI_OP_PORTSC ( port->address ) );
        change = ( portsc & EHCI_PORTSC_CHANGE );
        if ( ! change )
                return;

        /* Record disconnections and clear changes */
        port->disconnected |= ( portsc & EHCI_PORTSC_CSC );
        writel ( portsc, ehci->op + EHCI_OP_PORTSC ( port->address ) );

        /* Report port status change */
        usb_port_changed ( port );
}

/******************************************************************************
 *
 * Bus operations
 *
 ******************************************************************************
 */

/**
 * Open USB bus
 *
 * @v bus               USB bus
 * @ret rc              Return status code
 */
static int ehci_bus_open ( struct usb_bus *bus ) {
        struct ehci_device *ehci = usb_bus_get_hostdata ( bus );
        unsigned int frames;
        size_t len;
        int rc;

        /* Sanity checks */
        assert ( list_empty ( &ehci->async ) );
        assert ( list_empty ( &ehci->periodic ) );

        /* Allocate and initialise asynchronous queue head */
        ehci->head = malloc_phys ( sizeof ( *ehci->head ),
                                   ehci_align ( sizeof ( *ehci->head ) ) );
        if ( ! ehci->head ) {
                rc = -ENOMEM;
                goto err_alloc_head;
        }
        memset ( ehci->head, 0, sizeof ( *ehci->head ) );
        ehci->head->chr = cpu_to_le32 ( EHCI_CHR_HEAD );
        ehci->head->cache.next = cpu_to_le32 ( EHCI_LINK_TERMINATE );
        ehci->head->cache.status = EHCI_STATUS_HALTED;
        ehci_async_schedule ( ehci );
        writel ( virt_to_phys ( ehci->head ),
                 ehci->op + EHCI_OP_ASYNCLISTADDR );

        /* Use async queue head to determine control data structure segment */
        ehci->ctrldssegment =
                ( ( ( uint64_t ) virt_to_phys ( ehci->head ) ) >> 32 );
        if ( ehci->addr64 ) {
                writel ( ehci->ctrldssegment, ehci->op + EHCI_OP_CTRLDSSEGMENT);
        } else if ( ehci->ctrldssegment ) {
                DBGC ( ehci, "EHCI %s CTRLDSSEGMENT not supported\n",
                       ehci->name );
                rc = -ENOTSUP;
                goto err_ctrldssegment;
        }

        /* Allocate periodic frame list */
        frames = EHCI_PERIODIC_FRAMES ( ehci->flsize );
        len = ( frames * sizeof ( ehci->frame[0] ) );
        ehci->frame = malloc_phys ( len, EHCI_PAGE_ALIGN );
        if ( ! ehci->frame ) {
                rc = -ENOMEM;
                goto err_alloc_frame;
        }
        if ( ( rc = ehci_ctrl_reachable ( ehci, ehci->frame ) ) != 0 ) {
                DBGC ( ehci, "EHCI %s frame list unreachable\n", ehci->name );
                goto err_unreachable_frame;
        }
        ehci_periodic_schedule ( ehci );
        writel ( virt_to_phys ( ehci->frame ),
                 ehci->op + EHCI_OP_PERIODICLISTBASE );

        /* Start controller */
        ehci_run ( ehci );

        return 0;

        ehci_stop ( ehci );
 err_unreachable_frame:
        free_phys ( ehci->frame, len );
 err_alloc_frame:
 err_ctrldssegment:
        free_phys ( ehci->head, sizeof ( *ehci->head ) );
 err_alloc_head:
        return rc;
}

/**
 * Close USB bus
 *
 * @v bus               USB bus
 */
static void ehci_bus_close ( struct usb_bus *bus ) {
        struct ehci_device *ehci = usb_bus_get_hostdata ( bus );
        unsigned int frames = EHCI_PERIODIC_FRAMES ( ehci->flsize );

        /* Sanity checks */
        assert ( list_empty ( &ehci->async ) );
        assert ( list_empty ( &ehci->periodic ) );

        /* Stop controller */
        ehci_stop ( ehci );

        /* Free periodic frame list */
        free_phys ( ehci->frame, ( frames * sizeof ( ehci->frame[0] ) ) );

        /* Free asynchronous schedule */
        free_phys ( ehci->head, sizeof ( *ehci->head ) );
}

/**
 * Poll USB bus
 *
 * @v bus               USB bus
 */
static void ehci_bus_poll ( struct usb_bus *bus ) {
        struct ehci_device *ehci = usb_bus_get_hostdata ( bus );
        struct usb_hub *hub = bus->hub;
        struct ehci_endpoint *endpoint;
        unsigned int i;
        uint32_t usbsts;
        uint32_t change;

        /* Do nothing unless something has changed */
        usbsts = readl ( ehci->op + EHCI_OP_USBSTS );
        assert ( usbsts & EHCI_USBSTS_ASYNC );
        assert ( usbsts & EHCI_USBSTS_PERIODIC );
        assert ( ! ( usbsts & EHCI_USBSTS_HCH ) );
        change = ( usbsts & EHCI_USBSTS_CHANGE );
        if ( ! change )
                return;

        /* Acknowledge changes */
        writel ( usbsts, ehci->op + EHCI_OP_USBSTS );

        /* Process completions, if applicable */
        if ( change & ( EHCI_USBSTS_USBINT | EHCI_USBSTS_USBERRINT ) ) {

                /* Iterate over all endpoints looking for completed
                 * descriptors.  We trust that completion handlers are
                 * minimal and will not do anything that could
                 * plausibly affect the endpoint list itself.
                 */
                list_for_each_entry ( endpoint, &ehci->endpoints, list )
                        ehci_endpoint_poll ( endpoint );
        }

        /* Process port status changes, if applicable */
        if ( change & EHCI_USBSTS_PORT ) {

                /* Iterate over all ports looking for status changes */
                for ( i = 1 ; i <= ehci->ports ; i++ )
                        ehci_root_poll ( hub, usb_port ( hub, i ) );
        }

        /* Report fatal errors */
        if ( change & EHCI_USBSTS_SYSERR )
                DBGC ( ehci, "EHCI %s host system error\n", ehci->name );
}

/******************************************************************************
 *
 * PCI interface
 *
 ******************************************************************************
 */

/** USB host controller operations */
static struct usb_host_operations ehci_operations = {
        .endpoint = {
                .open = ehci_endpoint_open,
                .close = ehci_endpoint_close,
                .reset = ehci_endpoint_reset,
                .mtu = ehci_endpoint_mtu,
                .message = ehci_endpoint_message,
                .stream = ehci_endpoint_stream,
        },
        .device = {
                .open = ehci_device_open,
                .close = ehci_device_close,
                .address = ehci_device_address,
        },
        .bus = {
                .open = ehci_bus_open,
                .close = ehci_bus_close,
                .poll = ehci_bus_poll,
        },
        .hub = {
                .open = ehci_hub_open,
                .close = ehci_hub_close,
        },
        .root = {
                .open = ehci_root_open,
                .close = ehci_root_close,
                .enable = ehci_root_enable,
                .disable = ehci_root_disable,
                .speed = ehci_root_speed,
                .clear_tt = ehci_root_clear_tt,
        },
};

/**
 * Probe PCI device
 *
 * @v pci               PCI device
 * @ret rc              Return status code
 */
static int ehci_probe ( struct pci_device *pci ) {
        struct ehci_device *ehci;
        struct usb_port *port;
        unsigned long bar_start;
        size_t bar_size;
        unsigned int i;
        int rc;

        /* Allocate and initialise structure */
        ehci = zalloc ( sizeof ( *ehci ) );
        if ( ! ehci ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        ehci->name = pci->dev.name;
        INIT_LIST_HEAD ( &ehci->endpoints );
        INIT_LIST_HEAD ( &ehci->async );
        INIT_LIST_HEAD ( &ehci->periodic );

        /* Fix up PCI device */
        adjust_pci_device ( pci );

        /* Map registers */
        bar_start = pci_bar_start ( pci, EHCI_BAR );
        bar_size = pci_bar_size ( pci, EHCI_BAR );
        ehci->regs = pci_ioremap ( pci, bar_start, bar_size );
        if ( ! ehci->regs ) {
                rc = -ENODEV;
                goto err_ioremap;
        }

        /* Initialise EHCI device */
        ehci_init ( ehci, ehci->regs );

        /* Initialise USB legacy support and claim ownership */
        ehci_legacy_init ( ehci, pci );
        ehci_legacy_claim ( ehci, pci );

        /* Reset device */
        if ( ( rc = ehci_reset ( ehci ) ) != 0 )
                goto err_reset;

        /* Allocate USB bus */
        ehci->bus = alloc_usb_bus ( &pci->dev, ehci->ports, EHCI_MTU,
                                    &ehci_operations );
        if ( ! ehci->bus ) {
                rc = -ENOMEM;
                goto err_alloc_bus;
        }
        usb_bus_set_hostdata ( ehci->bus, ehci );
        usb_hub_set_drvdata ( ehci->bus->hub, ehci );

        /* Set port protocols */
        for ( i = 1 ; i <= ehci->ports ; i++ ) {
                port = usb_port ( ehci->bus->hub, i );
                port->protocol = USB_PROTO_2_0;
        }

        /* Register USB bus */
        if ( ( rc = register_usb_bus ( ehci->bus ) ) != 0 )
                goto err_register;

        pci_set_drvdata ( pci, ehci );
        return 0;

        unregister_usb_bus ( ehci->bus );
 err_register:
        free_usb_bus ( ehci->bus );
 err_alloc_bus:
        ehci_reset ( ehci );
 err_reset:
        ehci_legacy_release ( ehci, pci );
        iounmap ( ehci->regs );
 err_ioremap:
        free ( ehci );
 err_alloc:
        return rc;
}

/**
 * Remove PCI device
 *
 * @v pci               PCI device
 */
static void ehci_remove ( struct pci_device *pci ) {
        struct ehci_device *ehci = pci_get_drvdata ( pci );
        struct usb_bus *bus = ehci->bus;

        unregister_usb_bus ( bus );
        assert ( list_empty ( &ehci->async ) );
        assert ( list_empty ( &ehci->periodic ) );
        free_usb_bus ( bus );
        ehci_reset ( ehci );
        ehci_legacy_release ( ehci, pci );
        iounmap ( ehci->regs );
        free ( ehci );
}

/** EHCI PCI device IDs */
static struct pci_device_id ehci_ids[] = {
        PCI_ROM ( 0xffff, 0xffff, "ehci", "EHCI", 0 ),
};

/** EHCI PCI driver */
struct pci_driver ehci_driver __pci_driver = {
        .ids = ehci_ids,
        .id_count = ( sizeof ( ehci_ids ) / sizeof ( ehci_ids[0] ) ),
        .class = PCI_CLASS_ID ( PCI_CLASS_SERIAL, PCI_CLASS_SERIAL_USB,
                                PCI_CLASS_SERIAL_USB_EHCI ),
        .probe = ehci_probe,
        .remove = ehci_remove,
};

/**
 * Prepare for exit
 *
 * @v booting           System is shutting down for OS boot
 */
static void ehci_shutdown ( int booting ) {
        /* If we are shutting down to boot an OS, then prevent the
         * release of ownership back to BIOS.
         */
        ehci_legacy_prevent_release = booting;
}

/** Startup/shutdown function */
struct startup_fn ehci_startup __startup_fn ( STARTUP_LATE ) = {
        .name = "ehci",
        .shutdown = ehci_shutdown,
};