ecam.c

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/*
 * Copyright (C) 2022 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 <string.h>
#include <errno.h>
#include <ipxe/ecam.h>

/** @file
 *
 * PCI Enhanced Configuration Access Mechanism (ECAM)
 *
 */

/** Cached mapped ECAM allocation */
static struct ecam_mapping ecam;

/**
 * Find lowest ECAM allocation not below a given PCI bus:dev.fn address
 *
 * @v busdevfn          PCI bus:dev.fn address
 * @v range             PCI device address range to fill in
 * @v alloc             ECAM allocation to fill in, or NULL
 * @ret rc              Return status code
 */
static int ecam_find ( uint32_t busdevfn, struct pci_range *range,
                       struct ecam_allocation *alloc ) {
        struct ecam_table *mcfg;
        struct ecam_allocation *tmp;
        unsigned int best = 0;
        unsigned int count;
        unsigned int index;
        unsigned int i;
        uint32_t start;

        /* Return empty range on error */
        range->count = 0;

        /* Locate MCFG table */
        mcfg = container_of ( acpi_table ( ECAM_SIGNATURE, 0 ),
                              struct ecam_table, acpi );
        if ( ! mcfg ) {
                DBGC ( &ecam, "ECAM found no MCFG table\n" );
                return -ENOTSUP;
        }

        /* Iterate over allocations */
        for ( i = 0 ; ( offsetof ( typeof ( *mcfg ), alloc[ i + 1 ] ) <=
                        le32_to_cpu ( mcfg->acpi.length ) ) ; i++ ) {

                /* Read allocation */
                tmp = &mcfg->alloc[i];
                DBGC2 ( &ecam, "ECAM %04x:[%02x-%02x] has base %08llx\n",
                        le16_to_cpu ( tmp->segment ), tmp->start, tmp->end,
                        ( ( unsigned long long ) le64_to_cpu ( tmp->base ) ) );
                start = PCI_BUSDEVFN ( le16_to_cpu ( tmp->segment ),
                                       tmp->start, 0, 0 );
                count = PCI_BUSDEVFN ( 0, ( tmp->end - tmp->start + 1 ), 0, 0 );

                /* Check for a matching or new closest allocation */
                index = ( busdevfn - start );
                if ( ( index < count ) || ( index > best ) ) {
                        if ( alloc )
                                memcpy ( alloc, tmp, sizeof ( *alloc ) );
                        range->start = start;
                        range->count = count;
                        best = index;
                }

                /* Stop if this range contains the target bus:dev.fn address */
                if ( index < count )
                        return 0;
        }

        return ( best ? 0 : -ENOENT );
}

/**
 * Find next PCI bus:dev.fn address range in system
 *
 * @v busdevfn          Starting PCI bus:dev.fn address
 * @v range             PCI bus:dev.fn address range to fill in
 */
static void ecam_discover ( uint32_t busdevfn, struct pci_range *range ) {

        /* Find new range, if any */
        ecam_find ( busdevfn, range, NULL );
}

/**
 * Access configuration space for PCI device
 *
 * @v pci               PCI device
 * @ret rc              Return status code
 */
static int ecam_access ( struct pci_device *pci ) {
        uint64_t base;
        size_t len;
        int rc;

        /* Reuse mapping if possible */
        if ( ( pci->busdevfn - ecam.range.start ) < ecam.range.count )
                return ecam.rc;

        /* Clear any existing mapping */
        if ( ecam.regs ) {
                iounmap ( ecam.regs );
                ecam.regs = NULL;
        }

        /* Find allocation for this PCI device */
        if ( ( rc = ecam_find ( pci->busdevfn, &ecam.range,
                                &ecam.alloc ) ) != 0 ) {
                DBGC ( &ecam, "ECAM found no allocation for " PCI_FMT ": %s\n",
                       PCI_ARGS ( pci ), strerror ( rc ) );
                goto err_find;
        }
        if ( ecam.range.start > pci->busdevfn ) {
                DBGC ( &ecam, "ECAM found no allocation for " PCI_FMT "\n",
                       PCI_ARGS ( pci ) );
                rc = -ENOENT;
                goto err_find;
        }

        /* Map configuration space for this allocation */
        base = le64_to_cpu ( ecam.alloc.base );
        base += ( ecam.alloc.start * ECAM_SIZE * PCI_BUSDEVFN ( 0, 1, 0, 0 ) );
        len = ( ecam.range.count * ECAM_SIZE );
        if ( base != ( ( unsigned long ) base ) ) {
                DBGC ( &ecam, "ECAM %04x:[%02x-%02x] could not map "
                       "[%08llx,%08llx) outside CPU range\n",
                       le16_to_cpu ( ecam.alloc.segment ), ecam.alloc.start,
                       ecam.alloc.end, base, ( base + len ) );
                rc = -ERANGE;
                goto err_range;
        }
        ecam.regs = ioremap ( base, len );
        if ( ! ecam.regs ) {
                DBGC ( &ecam, "ECAM %04x:[%02x-%02x] could not map "
                       "[%08llx,%08llx)\n", le16_to_cpu ( ecam.alloc.segment ),
                       ecam.alloc.start, ecam.alloc.end, base, ( base + len ) );
                rc = -ENODEV;
                goto err_ioremap;
        }

        /* Populate cached mapping */
        DBGC ( &ecam, "ECAM %04x:[%02x-%02x] mapped [%08llx,%08llx) -> %p\n",
               le16_to_cpu ( ecam.alloc.segment ), ecam.alloc.start,
               ecam.alloc.end, base, ( base + len ), ecam.regs );
        ecam.rc = 0;
        return 0;

        iounmap ( ecam.regs );
 err_ioremap:
 err_range:
 err_find:
        ecam.rc = rc;
        return rc;
}

/**
 * Read from PCI configuration space
 *
 * @v pci       PCI device
 * @v location  Offset and length within PCI configuration space
 * @v value     Value read
 * @ret rc      Return status code
 */
int ecam_read ( struct pci_device *pci, unsigned int location, void *value ) {
        unsigned int where = ECAM_WHERE ( location );
        unsigned int len = ECAM_LEN ( location );
        unsigned int index;
        void *addr;
        int rc;

        /* Return all-ones on error */
        memset ( value, 0xff, len );

        /* Access configuration space */
        if ( ( rc = ecam_access ( pci ) ) != 0 )
                return rc;

        /* Read from address */
        index = ( pci->busdevfn - ecam.range.start );
        addr = ( ecam.regs + ( index * ECAM_SIZE ) + where );
        switch ( len ) {
        case 4:
                *( ( uint32_t *) value ) = readl ( addr );
                break;
        case 2:
                *( ( uint16_t *) value ) = readw ( addr );
                break;
        case 1:
                *( ( uint8_t *) value ) = readb ( addr );
                break;
        default:
                assert ( 0 );
        }

        return 0;
}

/**
 * Write to PCI configuration space
 *
 * @v pci       PCI device
 * @v location  Offset and length within PCI configuration space
 * @v value     Value to write
 * @ret rc      Return status code
 */
int ecam_write ( struct pci_device *pci, unsigned int location,
                 unsigned long value ) {
        unsigned int where = ECAM_WHERE ( location );
        unsigned int len = ECAM_LEN ( location );
        unsigned int index;
        void *addr;
        int rc;

        /* Access configuration space */
        if ( ( rc = ecam_access ( pci ) ) != 0 )
                return rc;

        /* Write to address */
        index = ( pci->busdevfn - ecam.range.start );
        addr = ( ecam.regs + ( index * ECAM_SIZE ) + where );
        switch ( len ) {
        case 4:
                writel ( value, addr );
                break;
        case 2:
                writew ( value, addr );
                break;
        case 1:
                writeb ( value, addr );
                break;
        default:
                assert ( 0 );
        }

        /* Read from address, to guarantee completion of the write
         *
         * PCIe configuration space registers may not have read side
         * effects.  Reading back is therefore always safe to do, and
         * guarantees that the write has reached the device.
         */
        mb();
        ecam_read ( pci, location, &value );

        return 0;
}

PROVIDE_PCIAPI_INLINE ( ecam, pci_can_probe );
PROVIDE_PCIAPI ( ecam, pci_discover, ecam_discover );
PROVIDE_PCIAPI_INLINE ( ecam, pci_read_config_byte );
PROVIDE_PCIAPI_INLINE ( ecam, pci_read_config_word );
PROVIDE_PCIAPI_INLINE ( ecam, pci_read_config_dword );
PROVIDE_PCIAPI_INLINE ( ecam, pci_write_config_byte );
PROVIDE_PCIAPI_INLINE ( ecam, pci_write_config_word );
PROVIDE_PCIAPI_INLINE ( ecam, pci_write_config_dword );
PROVIDE_PCIAPI_INLINE ( ecam, pci_ioremap );
PROVIDE_PCIAPI_RUNTIME ( ecam, PCIAPI_PRIORITY_ECAM );