cgem.c

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/*
 * Copyright (C) 2025 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 <stdint.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <byteswap.h>
#include <ipxe/netdevice.h>
#include <ipxe/ethernet.h>
#include <ipxe/if_ether.h>
#include <ipxe/iobuf.h>
#include <ipxe/timer.h>
#include <ipxe/devtree.h>
#include <ipxe/fdt.h>
#include "cgem.h"

/** @file
 *
 * Cadence Gigabit Ethernet MAC (GEM) network driver
 *
 * Based primarily on the Zynq 7000 SoC Technical Reference Manual,
 * available at the time of writing from:
 *
 *     https://docs.amd.com/r/en-US/ug585-zynq-7000-SoC-TRM
 *
 */

/******************************************************************************
 *
 * Device reset
 *
 ******************************************************************************
 */

/**
 * Reset hardware
 *
 * @v cgem              Cadence GEM device
 * @ret rc              Return status code
 */
static int cgem_reset ( struct cgem_nic *cgem ) {

        /* There is no software-driven reset capability in the
         * hardware.  Instead we have to write the expected reset
         * values to the various registers.
         */

        /* Disable all interrupts */
        writel ( CGEM_IDR_ALL, ( cgem->regs + CGEM_IDR ) );

        /* Clear network control register */
        writel ( 0, ( cgem->regs + CGEM_NWCTRL ) );

        /* Clear statistics registers now that TX and RX are stopped */
        writel ( CGEM_NWCTRL_STATCLR, ( cgem->regs + CGEM_NWCTRL ) );

        /* Clear TX queue base address */
        writel ( 0, ( cgem->regs + CGEM_TXQBASE ) );

        /* Clear RX queue base address */
        writel ( 0, ( cgem->regs + CGEM_RXQBASE ) );

        /* Configure DMA */
        writel ( ( CGEM_DMACR_RXBUF ( CGEM_RX_LEN ) | CGEM_DMACR_TXSIZE_MAX |
                   CGEM_DMACR_RXSIZE_MAX | CGEM_DMACR_BLENGTH_MAX ),
                 ( cgem->regs + CGEM_DMACR ) );

        /* Enable MII interface */
        writel ( CGEM_NWCTRL_MDEN, ( cgem->regs + CGEM_NWCTRL ) );

        return 0;
}

/******************************************************************************
 *
 * PHY access
 *
 ******************************************************************************
 */

/**
 * Wait for MII operation to complete
 *
 * @v cgem              Cadence GEM device
 * @ret rc              Return status code
 */
static int cgem_mii_wait ( struct cgem_nic *cgem ) {
        uint32_t nwsr;
        unsigned int i;

        /* Wait for MII interface to become idle */
        for ( i = 0 ; i < CGEM_MII_MAX_WAIT_US ; i++ ) {

                /* Check if MII interface is idle */
                nwsr = readl ( cgem->regs + CGEM_NWSR );
                if ( nwsr & CGEM_NWSR_MII_IDLE )
                        return 0;

                /* Delay */
                udelay ( 1 );
        }

        DBGC ( cgem, "CGEM %s timed out waiting for MII\n", cgem->name );
        return -ETIMEDOUT;
}

/**
 * Read from MII register
 *
 * @v mdio              MII interface
 * @v phy               PHY address
 * @v reg               Register address
 * @ret data            Data read, or negative error
 */
static int cgem_mii_read ( struct mii_interface *mdio, unsigned int phy,
                           unsigned int reg ) {
        struct cgem_nic *cgem = container_of ( mdio, struct cgem_nic, mdio );
        unsigned int data;
        int rc;

        /* Initiate read */
        writel ( ( CGEM_PHYMNTNC_CLAUSE22 | CGEM_PHYMNTNC_OP_READ |
                   CGEM_PHYMNTNC_ADDR ( phy ) | CGEM_PHYMNTNC_REG ( reg ) |
                   CGEM_PHYMNTNC_FIXED ),
                 ( cgem->regs + CGEM_PHYMNTNC ) );

        /* Wait for read to complete */
        if ( ( rc = cgem_mii_wait ( cgem ) ) != 0 )
                return rc;

        /* Read data */
        data = ( readl ( cgem->regs + CGEM_PHYMNTNC ) &
                 CGEM_PHYMNTNC_DATA_MASK );

        return data;
}

/**
 * Write to MII register
 *
 * @v mdio              MII interface
 * @v phy               PHY address
 * @v reg               Register address
 * @v data              Data to write
 * @ret rc              Return status code
 */
static int cgem_mii_write ( struct mii_interface *mdio, unsigned int phy,
                            unsigned int reg, unsigned int data ) {
        struct cgem_nic *cgem = container_of ( mdio, struct cgem_nic, mdio );
        int rc;

        /* Initiate write */
        writel ( ( CGEM_PHYMNTNC_CLAUSE22 | CGEM_PHYMNTNC_OP_READ |
                   CGEM_PHYMNTNC_ADDR ( phy ) | CGEM_PHYMNTNC_REG ( reg ) |
                   CGEM_PHYMNTNC_FIXED | data ),
                 ( cgem->regs + CGEM_PHYMNTNC ) );

        /* Wait for write to complete */
        if ( ( rc = cgem_mii_wait ( cgem ) ) != 0 )
                return rc;

        return 0;
}

/** MII operations */
static struct mii_operations cgem_mii_operations = {
        .read = cgem_mii_read,
        .write = cgem_mii_write,
};

/******************************************************************************
 *
 * Link state
 *
 ******************************************************************************
 */

/**
 * Initialise PHY
 *
 * @v cgem              Cadence GEM device
 * @ret rc              Return status code
 */
static int cgem_init_phy ( struct cgem_nic *cgem ) {
        int rc;

        /* Find PHY address */
        if ( ( rc = mii_find ( &cgem->mii ) ) != 0 ) {
                DBGC ( cgem, "CGEM %s could not find PHY address: %s\n",
                       cgem->name, strerror ( rc ) );
                return rc;
        }

        /* Reset PHY */
        if ( ( rc = mii_reset ( &cgem->mii ) ) != 0 ) {
                DBGC ( cgem, "CGEM %s could not reset PHY: %s\n",
                       cgem->name, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Check link state
 *
 * @v netdev            Network device
 */
static int cgem_check_link ( struct net_device *netdev ) {
        struct cgem_nic *cgem = netdev->priv;
        int rc;

        /* Check link state */
        if ( ( rc = mii_check_link ( &cgem->mii, netdev ) ) != 0 ) {
                DBGC ( cgem, "CGEM %s could not check link: %s\n",
                       cgem->name, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Check link state periodically
 *
 * @v retry             Link state check timer
 * @v over              Failure indicator
 */
static void cgem_expired ( struct retry_timer *timer, int over __unused ) {
        struct cgem_nic *cgem = container_of ( timer, struct cgem_nic, timer );
        struct net_device *netdev = cgem->netdev;

        /* Restart timer */
        start_timer_fixed ( timer, CGEM_LINK_INTERVAL );

        /* Check link state */
        cgem_check_link ( netdev );
}

/******************************************************************************
 *
 * Network device interface
 *
 ******************************************************************************
 */

/**
 * Create descriptor ring
 *
 * @v cgem              Cadence GEM device
 * @v ring              Descriptor ring
 * @ret rc              Return status code
 */
static int cgem_create_ring ( struct cgem_nic *cgem, struct cgem_ring *ring ) {
        struct cgem_descriptor *desc;
        unsigned int i;

        /* Allocate descriptor ring (on its own size) */
        ring->desc = dma_alloc ( cgem->dma, &ring->map, ring->len, ring->len );
        if ( ! ring->desc )
                return -ENOMEM;

        /* Initialise descriptor ring */
        for ( i = 0 ; i < ring->count ; i++ ) {
                desc = &ring->desc[i];
                desc->addr = cpu_to_le32 ( CGEM_RX_ADDR_OWNED );
                desc->flags = cpu_to_le32 ( CGEM_TX_FL_OWNED );
        }
        desc = &ring->desc[ ring->count - 1 ];
        desc->addr |= cpu_to_le32 ( CGEM_RX_ADDR_WRAP );
        desc->flags |= cpu_to_le32 ( CGEM_TX_FL_WRAP );

        /* Program ring address */
        writel ( dma ( &ring->map, ring->desc ),
                 ( cgem->regs + ring->qbase ) );

        DBGC ( cgem, "CGEM %s ring %02x is at [%08lx,%08lx)\n",
               cgem->name, ring->qbase, virt_to_phys ( ring->desc ),
               ( virt_to_phys ( ring->desc ) + ring->len ) );
        return 0;
}

/**
 * Destroy descriptor ring
 *
 * @v cgem              Cadence GEM device
 * @v ring              Descriptor ring
 */
static void cgem_destroy_ring ( struct cgem_nic *cgem,
                                struct cgem_ring *ring ) {

        /* Clear ring address */
        writel ( 0, ( cgem->regs + ring->qbase ) );

        /* Free descriptor ring */
        dma_free ( &ring->map, ring->desc, ring->len );
        ring->desc = NULL;
        ring->prod = 0;
        ring->cons = 0;
}

/**
 * Refill receive descriptor ring
 *
 * @v cgem              Cadence GEM device
 */
static void cgem_refill_rx ( struct cgem_nic *cgem ) {
        struct cgem_descriptor *rx;
        struct io_buffer *iobuf;
        unsigned int rx_idx;
        uint32_t addr;

        /* Refill ring */
        while ( ( cgem->rx.prod - cgem->rx.cons ) != CGEM_NUM_RX_DESC ) {

                /* Allocate I/O buffer */
                iobuf = alloc_rx_iob ( CGEM_RX_LEN, cgem->dma );
                if ( ! iobuf ) {
                        /* Wait for next refill */
                        break;
                }

                /* Get next receive descriptor */
                rx_idx = ( cgem->rx.prod++ % CGEM_NUM_RX_DESC );
                rx = &cgem->rx.desc[rx_idx];

                /* Populate receive descriptor */
                rx->flags = 0;
                addr = 0;
                if ( ( cgem->rx.prod % CGEM_NUM_RX_DESC ) == 0 )
                        addr |= CGEM_RX_ADDR_WRAP;
                rx->addr = cpu_to_le32 ( addr | iob_dma ( iobuf ) );

                /* Record I/O buffer */
                assert ( cgem->rx_iobuf[rx_idx] == NULL );
                cgem->rx_iobuf[rx_idx] = iobuf;

                DBGC2 ( cgem, "CGEM %s RX %d is [%08lx,%08lx)\n",
                        cgem->name, rx_idx, virt_to_phys ( iobuf->data ),
                        ( virt_to_phys ( iobuf->data ) + CGEM_RX_LEN ) );
        }
}

/**
 * Open network device
 *
 * @v netdev            Network device
 * @ret rc              Return status code
 */
static int cgem_open ( struct net_device *netdev ) {
        struct cgem_nic *cgem = netdev->priv;
        union cgem_mac mac;
        int rc;

        /* Create transmit descriptor ring */
        if ( ( rc = cgem_create_ring ( cgem, &cgem->tx ) ) != 0 )
                goto err_create_tx;

        /* Create receive descriptor ring */
        if ( ( rc = cgem_create_ring ( cgem, &cgem->rx ) ) != 0 )
                goto err_create_rx;

        /* Set MAC address */
        memcpy ( mac.raw, netdev->ll_addr, ETH_ALEN );
        writel ( mac.reg.low, ( cgem->regs + CGEM_LADDRL ) );
        writel ( mac.reg.high, ( cgem->regs + CGEM_LADDRH ) );

        /* Enable transmit and receive */
        writel ( CGEM_NWCTRL_NORMAL, ( cgem->regs + CGEM_NWCTRL ) );

        /* Refill receive descriptor ring */
        cgem_refill_rx ( cgem );

        /* Update link state */
        cgem_check_link ( netdev );

        /* Start link state timer */
        start_timer_fixed ( &cgem->timer, CGEM_LINK_INTERVAL );

        return 0;

        cgem_destroy_ring ( cgem, &cgem->rx );
 err_create_rx:
        cgem_destroy_ring ( cgem, &cgem->tx );
 err_create_tx:
        return rc;
}

/**
 * Close network device
 *
 * @v netdev            Network device
 */
static void cgem_close ( struct net_device *netdev ) {
        struct cgem_nic *cgem = netdev->priv;
        unsigned int i;

        /* Stop link state timer */
        stop_timer ( &cgem->timer );

        /* Reset NIC */
        cgem_reset ( cgem );

        /* Discard unused receive buffers */
        for ( i = 0 ; i < CGEM_NUM_RX_DESC ; i++ ) {
                if ( cgem->rx_iobuf[i] )
                        free_rx_iob ( cgem->rx_iobuf[i] );
                cgem->rx_iobuf[i] = NULL;
        }

        /* Destroy receive descriptor ring */
        cgem_destroy_ring ( cgem, &cgem->rx );

        /* Destroy transmit descriptor ring */
        cgem_destroy_ring ( cgem, &cgem->tx );
}

/**
 * Transmit packet
 *
 * @v netdev            Network device
 * @v iobuf             I/O buffer
 * @ret rc              Return status code
 */
static int cgem_transmit ( struct net_device *netdev,
                           struct io_buffer *iobuf ) {
        struct cgem_nic *cgem = netdev->priv;
        struct cgem_descriptor *tx;
        unsigned int tx_idx;
        uint32_t flags;
        int rc;

        /* Get next transmit descriptor */
        if ( ( cgem->tx.prod - cgem->tx.cons ) >= CGEM_NUM_TX_DESC ) {
                DBGC ( cgem, "CGEM %s out of transmit descriptors\n",
                       cgem->name );
                return -ENOBUFS;
        }
        tx_idx = ( cgem->tx.prod % CGEM_NUM_TX_DESC );
        tx = &cgem->tx.desc[tx_idx];

        /* Pad to minimum length */
        iob_pad ( iobuf, ETH_ZLEN );

        /* Map I/O buffer */
        if ( ( rc = iob_map_tx ( iobuf, cgem->dma ) ) != 0 )
                return rc;

        /* Update producer index */
        cgem->tx.prod++;

        /* Populate transmit descriptor */
        flags = CGEM_TX_FL_LAST;
        if ( ( cgem->tx.prod % CGEM_NUM_TX_DESC ) == 0 )
                flags |= CGEM_TX_FL_WRAP;
        tx->addr = cpu_to_le32 ( iob_dma ( iobuf ) );
        wmb();
        tx->flags = cpu_to_le32 ( flags | iob_len ( iobuf ) );
        wmb();

        /* Initiate transmission */
        writel ( ( CGEM_NWCTRL_NORMAL | CGEM_NWCTRL_STARTTX ),
                 ( cgem->regs + CGEM_NWCTRL ) );

        DBGC2 ( cgem, "CGEM %s TX %d is [%08lx,%08lx)\n",
                cgem->name, tx_idx, virt_to_phys ( iobuf->data ),
                ( virt_to_phys ( iobuf->data ) + iob_len ( iobuf ) ) );
        return 0;
}

/**
 * Poll for completed packets
 *
 * @V netdev            Network device
 */
static void cgem_poll_tx ( struct net_device *netdev ) {
        struct cgem_nic *cgem = netdev->priv;
        struct cgem_descriptor *tx;
        unsigned int tx_idx;

        /* Check for completed packets */
        while ( cgem->tx.cons != cgem->tx.prod ) {

                /* Get next transmit descriptor */
                tx_idx = ( cgem->tx.cons % CGEM_NUM_TX_DESC );
                tx = &cgem->tx.desc[tx_idx];

                /* Stop if descriptor is still owned by hardware */
                if ( ! ( tx->flags & cpu_to_le32 ( CGEM_TX_FL_OWNED ) ) )
                        return;
                DBGC2 ( cgem, "CGEM %s TX %d complete\n",
                        cgem->name, tx_idx );

                /* Complete transmit descriptor */
                netdev_tx_complete_next ( netdev );
                cgem->tx.cons++;
        }
}

/**
 * Poll for received packets
 *
 * @v netdev            Network device
 */
static void cgem_poll_rx ( struct net_device *netdev ) {
        struct cgem_nic *cgem = netdev->priv;
        struct cgem_descriptor *rx;
        struct io_buffer *iobuf;
        unsigned int rx_idx;
        uint32_t flags;
        size_t len;

        /* Check for received packets */
        while ( cgem->rx.cons != cgem->rx.prod ) {

                /* Get next receive descriptor */
                rx_idx = ( cgem->rx.cons % CGEM_NUM_RX_DESC );
                rx = &cgem->rx.desc[rx_idx];

                /* Stop if descriptor is still in use */
                if ( ! ( rx->addr & cpu_to_le32 ( CGEM_RX_ADDR_OWNED ) ) )
                        return;

                /* Populate I/O buffer */
                iobuf = cgem->rx_iobuf[rx_idx];
                cgem->rx_iobuf[rx_idx] = NULL;
                flags = le32_to_cpu ( rx->flags );
                len = CGEM_RX_FL_LEN ( flags );
                iob_put ( iobuf, len );
                DBGC2 ( cgem, "CGEM %s RX %d complete (length %zd)\n",
                        cgem->name, rx_idx, len );

                /* Hand off to network stack */
                netdev_rx ( netdev, iobuf );
                cgem->rx.cons++;
        }
}

/**
 * Poll for completed and received packets
 *
 * @v netdev            Network device
 */
static void cgem_poll ( struct net_device *netdev ) {
        struct cgem_nic *cgem = netdev->priv;

        /* Poll for TX competions */
        cgem_poll_tx ( netdev );

        /* Poll for RX completions */
        cgem_poll_rx ( netdev );

        /* Refill RX ring */
        cgem_refill_rx ( cgem );
}

/** Cadence GEM network device operations */
static struct net_device_operations cgem_operations = {
        .open           = cgem_open,
        .close          = cgem_close,
        .transmit       = cgem_transmit,
        .poll           = cgem_poll,
};

/******************************************************************************
 *
 * Devicetree interface
 *
 ******************************************************************************
 */

/**
 * Probe devicetree device
 *
 * @v dt                Devicetree device
 * @v offset            Starting node offset
 * @ret rc              Return status code
 */
static int cgem_probe ( struct dt_device *dt, unsigned int offset ) {
        struct net_device *netdev;
        struct cgem_nic *cgem;
        union cgem_mac mac;
        int rc;

        /* Allocate and initialise net device */
        netdev = alloc_etherdev ( sizeof ( *cgem ) );
        if ( ! netdev ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        netdev_init ( netdev, &cgem_operations );
        cgem = netdev->priv;
        dt_set_drvdata ( dt, netdev );
        netdev->dev = &dt->dev;
        memset ( cgem, 0, sizeof ( *cgem ) );
        cgem->dma = &dt->dma;
        cgem->netdev = netdev;
        cgem->name = netdev->dev->name;
        mdio_init ( &cgem->mdio, &cgem_mii_operations );
        mii_init ( &cgem->mii, &cgem->mdio, 0 );
        timer_init ( &cgem->timer, cgem_expired, &netdev->refcnt );
        cgem_init_ring ( &cgem->tx, CGEM_NUM_TX_DESC, CGEM_TXQBASE );
        cgem_init_ring ( &cgem->rx, CGEM_NUM_RX_DESC, CGEM_RXQBASE );

        /* Map registers */
        cgem->regs = dt_ioremap ( dt, offset, CGEM_REG_IDX, CGEM_REG_LEN );
        if ( ! cgem->regs ) {
                rc = -ENODEV;
                goto err_ioremap;
        }

        /* Reset the NIC */
        if ( ( rc = cgem_reset ( cgem ) ) != 0 )
                goto err_reset;

        /* Initialise the PHY */
        if ( ( rc = cgem_init_phy ( cgem ) ) != 0 )
                goto err_init_phy;

        /* Fetch devicetree MAC address */
        if ( ( rc = fdt_mac ( &sysfdt, offset, netdev ) ) != 0 ) {
                DBGC ( cgem, "CGEM %s could not fetch MAC: %s\n",
                       cgem->name, strerror ( rc ) );
                goto err_mac;
        }

        /* Fetch current MAC address, if set */
        mac.reg.low = readl ( cgem->regs + CGEM_LADDRL );
        mac.reg.high = readl ( cgem->regs + CGEM_LADDRH );
        memcpy ( netdev->ll_addr, mac.raw, ETH_ALEN );

        /* Register network device */
        if ( ( rc = register_netdev ( netdev ) ) != 0 )
                goto err_register_netdev;

        /* Set initial link state */
        cgem_check_link ( netdev );

        return 0;

        unregister_netdev ( netdev );
 err_register_netdev:
 err_mac:
 err_init_phy:
        cgem_reset ( cgem );
 err_reset:
        iounmap ( cgem->regs );
 err_ioremap:
        netdev_nullify ( netdev );
        netdev_put ( netdev );
 err_alloc:
        return rc;
}

/**
 * Remove devicetree device
 *
 * @v dt                Devicetree device
 */
static void cgem_remove ( struct dt_device *dt ) {
        struct net_device *netdev = dt_get_drvdata ( dt );
        struct cgem_nic *cgem = netdev->priv;

        /* Unregister network device */
        unregister_netdev ( netdev );

        /* Reset card */
        cgem_reset ( cgem );

        /* Free network device */
        iounmap ( cgem->regs );
        netdev_nullify ( netdev );
        netdev_put ( netdev );
}

/** Cadence GEM compatible model identifiers */
static const char * cgem_ids[] = {
        "sifive,fu540-c000-gem",
};

/** Cadence GEM devicetree driver */
struct dt_driver cgem_driver __dt_driver = {
        .name = "cgem",
        .ids = cgem_ids,
        .id_count = ( sizeof ( cgem_ids ) / sizeof ( cgem_ids[0] ) ),
        .probe = cgem_probe,
        .remove = cgem_remove,
};