// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  sata_via.c - VIA Serial ATA controllers
 *
 *  Maintained by:  Tejun Heo <tj@kernel.org>
 *                 Please ALWAYS copy linux-ide@vger.kernel.org
 *                 on emails.
 *
 *  Copyright 2003-2004 Red Hat, Inc.  All rights reserved.
 *  Copyright 2003-2004 Jeff Garzik
 *
 *  libata documentation is available via 'make {ps|pdf}docs',
 *  as Documentation/driver-api/libata.rst
 *
 *  Hardware documentation available under NDA.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_host.h>
#include <linux/libata.h>
#include <linux/string_choices.h>

#define DRV_NAME        "sata_via"
#define DRV_VERSION     "2.6"

/*
 * vt8251 is different from other sata controllers of VIA.  It has two
 * channels, each channel has both Master and Slave slot.
 */
enum board_ids_enum {
        vt6420,
        vt6421,
        vt8251,
};

enum {
        SATA_CHAN_ENAB          = 0x40, /* SATA channel enable */
        SATA_INT_GATE           = 0x41, /* SATA interrupt gating */
        SATA_NATIVE_MODE        = 0x42, /* Native mode enable */
        SVIA_MISC_3             = 0x46, /* Miscellaneous Control III */
        PATA_UDMA_TIMING        = 0xB3, /* PATA timing for DMA/ cable detect */
        PATA_PIO_TIMING         = 0xAB, /* PATA timing register */

        PORT0                   = (1 << 1),
        PORT1                   = (1 << 0),
        ALL_PORTS               = PORT0 | PORT1,

        NATIVE_MODE_ALL         = (1 << 7) | (1 << 6) | (1 << 5) | (1 << 4),

        SATA_EXT_PHY            = (1 << 6), /* 0==use PATA, 1==ext phy */

        SATA_HOTPLUG            = (1 << 5), /* enable IRQ on hotplug */
};

struct svia_priv {
        bool                    wd_workaround;
};

static int vt6420_hotplug;
module_param_named(vt6420_hotplug, vt6420_hotplug, int, 0644);
MODULE_PARM_DESC(vt6420_hotplug, "Enable hot-plug support for VT6420 (0=Don't support, 1=support)");

static int svia_init_one(struct pci_dev *pdev, const struct pci_device_id *ent);
#ifdef CONFIG_PM_SLEEP
static int svia_pci_device_resume(struct pci_dev *pdev);
#endif
static int svia_scr_read(struct ata_link *link, unsigned int sc_reg, u32 *val);
static int svia_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val);
static int vt8251_scr_read(struct ata_link *link, unsigned int scr, u32 *val);
static int vt8251_scr_write(struct ata_link *link, unsigned int scr, u32 val);
static void svia_tf_load(struct ata_port *ap, const struct ata_taskfile *tf);
static void svia_noop_freeze(struct ata_port *ap);
static int vt6420_prereset(struct ata_link *link, unsigned long deadline);
static void vt6420_bmdma_start(struct ata_queued_cmd *qc);
static int vt6421_pata_cable_detect(struct ata_port *ap);
static void vt6421_set_pio_mode(struct ata_port *ap, struct ata_device *adev);
static void vt6421_set_dma_mode(struct ata_port *ap, struct ata_device *adev);
static void vt6421_error_handler(struct ata_port *ap);

static const struct pci_device_id svia_pci_tbl[] = {
        { PCI_VDEVICE(VIA, 0x5337), vt6420 },
        { PCI_VDEVICE(VIA, 0x0591), vt6420 }, /* 2 sata chnls (Master) */
        { PCI_VDEVICE(VIA, 0x3149), vt6420 }, /* 2 sata chnls (Master) */
        { PCI_VDEVICE(VIA, 0x3249), vt6421 }, /* 2 sata chnls, 1 pata chnl */
        { PCI_VDEVICE(VIA, 0x5372), vt6420 },
        { PCI_VDEVICE(VIA, 0x7372), vt6420 },
        { PCI_VDEVICE(VIA, 0x5287), vt8251 }, /* 2 sata chnls (Master/Slave) */
        { PCI_VDEVICE(VIA, 0x9000), vt8251 },

        { }     /* terminate list */
};

static struct pci_driver svia_pci_driver = {
        .name                   = DRV_NAME,
        .id_table               = svia_pci_tbl,
        .probe                  = svia_init_one,
#ifdef CONFIG_PM_SLEEP
        .suspend                = ata_pci_device_suspend,
        .resume                 = svia_pci_device_resume,
#endif
        .remove                 = ata_pci_remove_one,
};

static const struct scsi_host_template svia_sht = {
        ATA_BMDMA_SHT(DRV_NAME),
};

static struct ata_port_operations svia_base_ops = {
        .inherits               = &ata_bmdma_port_ops,
        .sff_tf_load            = svia_tf_load,
};

static struct ata_port_operations vt6420_sata_ops = {
        .inherits               = &svia_base_ops,
        .freeze                 = svia_noop_freeze,
        .reset.prereset         = vt6420_prereset,
        .bmdma_start            = vt6420_bmdma_start,
};

static struct ata_port_operations vt6421_pata_ops = {
        .inherits               = &svia_base_ops,
        .cable_detect           = vt6421_pata_cable_detect,
        .set_piomode            = vt6421_set_pio_mode,
        .set_dmamode            = vt6421_set_dma_mode,
};

static struct ata_port_operations vt6421_sata_ops = {
        .inherits               = &svia_base_ops,
        .scr_read               = svia_scr_read,
        .scr_write              = svia_scr_write,
        .error_handler          = vt6421_error_handler,
};

static struct ata_port_operations vt8251_ops = {
        .inherits               = &svia_base_ops,
        .reset.hardreset        = sata_std_hardreset,
        .scr_read               = vt8251_scr_read,
        .scr_write              = vt8251_scr_write,
};

static const struct ata_port_info vt6420_port_info = {
        .flags          = ATA_FLAG_SATA,
        .pio_mask       = ATA_PIO4,
        .mwdma_mask     = ATA_MWDMA2,
        .udma_mask      = ATA_UDMA6,
        .port_ops       = &vt6420_sata_ops,
};

static const struct ata_port_info vt6421_sport_info = {
        .flags          = ATA_FLAG_SATA,
        .pio_mask       = ATA_PIO4,
        .mwdma_mask     = ATA_MWDMA2,
        .udma_mask      = ATA_UDMA6,
        .port_ops       = &vt6421_sata_ops,
};

static const struct ata_port_info vt6421_pport_info = {
        .flags          = ATA_FLAG_SLAVE_POSS,
        .pio_mask       = ATA_PIO4,
        /* No MWDMA */
        .udma_mask      = ATA_UDMA6,
        .port_ops       = &vt6421_pata_ops,
};

static const struct ata_port_info vt8251_port_info = {
        .flags          = ATA_FLAG_SATA | ATA_FLAG_SLAVE_POSS,
        .pio_mask       = ATA_PIO4,
        .mwdma_mask     = ATA_MWDMA2,
        .udma_mask      = ATA_UDMA6,
        .port_ops       = &vt8251_ops,
};

MODULE_AUTHOR("Jeff Garzik");
MODULE_DESCRIPTION("SCSI low-level driver for VIA SATA controllers");
MODULE_LICENSE("GPL");
MODULE_DEVICE_TABLE(pci, svia_pci_tbl);
MODULE_VERSION(DRV_VERSION);

static int svia_scr_read(struct ata_link *link, unsigned int sc_reg, u32 *val)
{
        if (sc_reg > SCR_CONTROL)
                return -EINVAL;
        *val = ioread32(link->ap->ioaddr.scr_addr + (4 * sc_reg));
        return 0;
}

static int svia_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val)
{
        if (sc_reg > SCR_CONTROL)
                return -EINVAL;
        iowrite32(val, link->ap->ioaddr.scr_addr + (4 * sc_reg));
        return 0;
}

static int vt8251_scr_read(struct ata_link *link, unsigned int scr, u32 *val)
{
        static const u8 ipm_tbl[] = { 1, 2, 6, 0 };
        struct pci_dev *pdev = to_pci_dev(link->ap->host->dev);
        int slot = 2 * link->ap->port_no + link->pmp;
        u32 v = 0;
        u8 raw;

        switch (scr) {
        case SCR_STATUS:
                pci_read_config_byte(pdev, 0xA0 + slot, &raw);

                /* read the DET field, bit0 and 1 of the config byte */
                v |= raw & 0x03;

                /* read the SPD field, bit4 of the configure byte */
                if (raw & (1 << 4))
                        v |= 0x02 << 4;
                else
                        v |= 0x01 << 4;

                /* read the IPM field, bit2 and 3 of the config byte */
                v |= ipm_tbl[(raw >> 2) & 0x3];
                break;

        case SCR_ERROR:
                /* devices other than 5287 uses 0xA8 as base */
                WARN_ON(pdev->device != 0x5287);
                pci_read_config_dword(pdev, 0xB0 + slot * 4, &v);
                break;

        case SCR_CONTROL:
                pci_read_config_byte(pdev, 0xA4 + slot, &raw);

                /* read the DET field, bit0 and bit1 */
                v |= ((raw & 0x02) << 1) | (raw & 0x01);

                /* read the IPM field, bit2 and bit3 */
                v |= ((raw >> 2) & 0x03) << 8;
                break;

        default:
                return -EINVAL;
        }

        *val = v;
        return 0;
}

static int vt8251_scr_write(struct ata_link *link, unsigned int scr, u32 val)
{
        struct pci_dev *pdev = to_pci_dev(link->ap->host->dev);
        int slot = 2 * link->ap->port_no + link->pmp;
        u32 v = 0;

        switch (scr) {
        case SCR_ERROR:
                /* devices other than 5287 uses 0xA8 as base */
                WARN_ON(pdev->device != 0x5287);
                pci_write_config_dword(pdev, 0xB0 + slot * 4, val);
                return 0;

        case SCR_CONTROL:
                /* set the DET field */
                v |= ((val & 0x4) >> 1) | (val & 0x1);

                /* set the IPM field */
                v |= ((val >> 8) & 0x3) << 2;

                pci_write_config_byte(pdev, 0xA4 + slot, v);
                return 0;

        default:
                return -EINVAL;
        }
}

/**
 *      svia_tf_load - send taskfile registers to host controller
 *      @ap: Port to which output is sent
 *      @tf: ATA taskfile register set
 *
 *      Outputs ATA taskfile to standard ATA host controller.
 *
 *      This is to fix the internal bug of via chipsets, which will
 *      reset the device register after changing the IEN bit on ctl
 *      register.
 */
static void svia_tf_load(struct ata_port *ap, const struct ata_taskfile *tf)
{
        struct ata_taskfile ttf;

        if (tf->ctl != ap->last_ctl)  {
                ttf = *tf;
                ttf.flags |= ATA_TFLAG_DEVICE;
                tf = &ttf;
        }
        ata_sff_tf_load(ap, tf);
}

static void svia_noop_freeze(struct ata_port *ap)
{
        /* Some VIA controllers choke if ATA_NIEN is manipulated in
         * certain way.  Leave it alone and just clear pending IRQ.
         */
        ap->ops->sff_check_status(ap);
        ata_bmdma_irq_clear(ap);
}

/**
 *      vt6420_prereset - prereset for vt6420
 *      @link: target ATA link
 *      @deadline: deadline jiffies for the operation
 *
 *      SCR registers on vt6420 are pieces of shit and may hang the
 *      whole machine completely if accessed with the wrong timing.
 *      To avoid such catastrophe, vt6420 doesn't provide generic SCR
 *      access operations, but uses SStatus and SControl only during
 *      boot probing in controlled way.
 *
 *      As the old (pre EH update) probing code is proven to work, we
 *      strictly follow the access pattern.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep)
 *
 *      RETURNS:
 *      0 on success, -errno otherwise.
 */
static int vt6420_prereset(struct ata_link *link, unsigned long deadline)
{
        struct ata_port *ap = link->ap;
        struct ata_eh_context *ehc = &ap->link.eh_context;
        unsigned long timeout = jiffies + (HZ * 5);
        u32 sstatus, scontrol;
        int online;

        /* don't do any SCR stuff if we're not loading */
        if (!(ap->pflags & ATA_PFLAG_LOADING))
                goto skip_scr;

        /* Resume phy.  This is the old SATA resume sequence */
        svia_scr_write(link, SCR_CONTROL, 0x300);
        svia_scr_read(link, SCR_CONTROL, &scontrol); /* flush */

        /* wait for phy to become ready, if necessary */
        do {
                ata_msleep(link->ap, 200);
                svia_scr_read(link, SCR_STATUS, &sstatus);
                if ((sstatus & 0xf) != 1)
                        break;
        } while (time_before(jiffies, timeout));

        /* open code sata_print_link_status() */
        svia_scr_read(link, SCR_STATUS, &sstatus);
        svia_scr_read(link, SCR_CONTROL, &scontrol);

        online = (sstatus & 0xf) == 0x3;

        ata_port_info(ap,
                      "SATA link %s 1.5 Gbps (SStatus %X SControl %X)\n",
                      str_up_down(online), sstatus, scontrol);

        /* SStatus is read one more time */
        svia_scr_read(link, SCR_STATUS, &sstatus);

        if (!online) {
                /* tell EH to bail */
                ehc->i.action &= ~ATA_EH_RESET;
                return 0;
        }

 skip_scr:
        /* wait for !BSY */
        ata_sff_wait_ready(link, deadline);

        return 0;
}

static void vt6420_bmdma_start(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        if ((qc->tf.command == ATA_CMD_PACKET) &&
            (qc->scsicmd->sc_data_direction == DMA_TO_DEVICE)) {
                /* Prevents corruption on some ATAPI burners */
                ata_sff_pause(ap);
        }
        ata_bmdma_start(qc);
}

static int vt6421_pata_cable_detect(struct ata_port *ap)
{
        struct pci_dev *pdev = to_pci_dev(ap->host->dev);
        u8 tmp;

        pci_read_config_byte(pdev, PATA_UDMA_TIMING, &tmp);
        if (tmp & 0x10)
                return ATA_CBL_PATA40;
        return ATA_CBL_PATA80;
}

static void vt6421_set_pio_mode(struct ata_port *ap, struct ata_device *adev)
{
        struct pci_dev *pdev = to_pci_dev(ap->host->dev);
        static const u8 pio_bits[] = { 0xA8, 0x65, 0x65, 0x31, 0x20 };
        pci_write_config_byte(pdev, PATA_PIO_TIMING - adev->devno,
                              pio_bits[adev->pio_mode - XFER_PIO_0]);
}

static void vt6421_set_dma_mode(struct ata_port *ap, struct ata_device *adev)
{
        struct pci_dev *pdev = to_pci_dev(ap->host->dev);
        static const u8 udma_bits[] = { 0xEE, 0xE8, 0xE6, 0xE4, 0xE2, 0xE1, 0xE0, 0xE0 };
        pci_write_config_byte(pdev, PATA_UDMA_TIMING - adev->devno,
                              udma_bits[adev->dma_mode - XFER_UDMA_0]);
}

static const unsigned int svia_bar_sizes[] = {
        8, 4, 8, 4, 16, 256
};

static const unsigned int vt6421_bar_sizes[] = {
        16, 16, 16, 16, 32, 128
};

static void __iomem *svia_scr_addr(void __iomem *addr, unsigned int port)
{
        return addr + (port * 128);
}

static void __iomem *vt6421_scr_addr(void __iomem *addr, unsigned int port)
{
        return addr + (port * 64);
}

static void vt6421_init_addrs(struct ata_port *ap)
{
        void __iomem * const * iomap = ap->host->iomap;
        void __iomem *reg_addr = iomap[ap->port_no];
        void __iomem *bmdma_addr = iomap[4] + (ap->port_no * 8);
        struct ata_ioports *ioaddr = &ap->ioaddr;

        ioaddr->cmd_addr = reg_addr;
        ioaddr->altstatus_addr =
        ioaddr->ctl_addr = (void __iomem *)
                ((unsigned long)(reg_addr + 8) | ATA_PCI_CTL_OFS);
        ioaddr->bmdma_addr = bmdma_addr;
        ioaddr->scr_addr = vt6421_scr_addr(iomap[5], ap->port_no);

        ata_sff_std_ports(ioaddr);

        ata_port_pbar_desc(ap, ap->port_no, -1, "port");
        ata_port_pbar_desc(ap, 4, ap->port_no * 8, "bmdma");
}

static int vt6420_prepare_host(struct pci_dev *pdev, struct ata_host **r_host)
{
        const struct ata_port_info *ppi[] = { &vt6420_port_info, NULL };
        struct ata_host *host;
        int rc;

        if (vt6420_hotplug) {
                ppi[0]->port_ops->scr_read = svia_scr_read;
                ppi[0]->port_ops->scr_write = svia_scr_write;
        }

        rc = ata_pci_bmdma_prepare_host(pdev, ppi, &host);
        if (rc)
                return rc;
        *r_host = host;

        rc = pcim_iomap_regions(pdev, 1 << 5, DRV_NAME);
        if (rc) {
                dev_err(&pdev->dev, "failed to iomap PCI BAR 5\n");
                return rc;
        }

        host->ports[0]->ioaddr.scr_addr = svia_scr_addr(host->iomap[5], 0);
        host->ports[1]->ioaddr.scr_addr = svia_scr_addr(host->iomap[5], 1);

        return 0;
}

static int vt6421_prepare_host(struct pci_dev *pdev, struct ata_host **r_host)
{
        const struct ata_port_info *ppi[] =
                { &vt6421_sport_info, &vt6421_sport_info, &vt6421_pport_info };
        struct ata_host *host;
        int i, rc;

        *r_host = host = ata_host_alloc_pinfo(&pdev->dev, ppi, ARRAY_SIZE(ppi));
        if (!host) {
                dev_err(&pdev->dev, "failed to allocate host\n");
                return -ENOMEM;
        }

        rc = pcim_iomap_regions(pdev, 0x3f, DRV_NAME);
        if (rc) {
                dev_err(&pdev->dev, "failed to request/iomap PCI BARs (errno=%d)\n",
                        rc);
                return rc;
        }
        host->iomap = pcim_iomap_table(pdev);

        for (i = 0; i < host->n_ports; i++)
                vt6421_init_addrs(host->ports[i]);

        return dma_set_mask_and_coherent(&pdev->dev, ATA_DMA_MASK);
}

static int vt8251_prepare_host(struct pci_dev *pdev, struct ata_host **r_host)
{
        const struct ata_port_info *ppi[] = { &vt8251_port_info, NULL };
        struct ata_host *host;
        int i, rc;

        rc = ata_pci_bmdma_prepare_host(pdev, ppi, &host);
        if (rc)
                return rc;
        *r_host = host;

        rc = pcim_iomap_regions(pdev, 1 << 5, DRV_NAME);
        if (rc) {
                dev_err(&pdev->dev, "failed to iomap PCI BAR 5\n");
                return rc;
        }

        /* 8251 hosts four sata ports as M/S of the two channels */
        for (i = 0; i < host->n_ports; i++)
                ata_slave_link_init(host->ports[i]);

        return 0;
}

static void svia_wd_fix(struct pci_dev *pdev)
{
        u8 tmp8;

        pci_read_config_byte(pdev, 0x52, &tmp8);
        pci_write_config_byte(pdev, 0x52, tmp8 | BIT(2));
}

static irqreturn_t vt642x_interrupt(int irq, void *dev_instance)
{
        struct ata_host *host = dev_instance;
        irqreturn_t rc = ata_bmdma_interrupt(irq, dev_instance);

        /* if the IRQ was not handled, it might be a hotplug IRQ */
        if (rc != IRQ_HANDLED) {
                u32 serror;
                unsigned long flags;

                spin_lock_irqsave(&host->lock, flags);
                /* check for hotplug on port 0 */
                svia_scr_read(&host->ports[0]->link, SCR_ERROR, &serror);
                if (serror & SERR_PHYRDY_CHG) {
                        ata_ehi_hotplugged(&host->ports[0]->link.eh_info);
                        ata_port_freeze(host->ports[0]);
                        rc = IRQ_HANDLED;
                }
                /* check for hotplug on port 1 */
                svia_scr_read(&host->ports[1]->link, SCR_ERROR, &serror);
                if (serror & SERR_PHYRDY_CHG) {
                        ata_ehi_hotplugged(&host->ports[1]->link.eh_info);
                        ata_port_freeze(host->ports[1]);
                        rc = IRQ_HANDLED;
                }
                spin_unlock_irqrestore(&host->lock, flags);
        }

        return rc;
}

static void vt6421_error_handler(struct ata_port *ap)
{
        struct svia_priv *hpriv = ap->host->private_data;
        struct pci_dev *pdev = to_pci_dev(ap->host->dev);
        u32 serror;

        /* see svia_configure() for description */
        if (!hpriv->wd_workaround) {
                svia_scr_read(&ap->link, SCR_ERROR, &serror);
                if (serror == 0x1000500) {
                        ata_port_warn(ap, "Incompatible drive: enabling workaround. This slows down transfer rate to ~60 MB/s");
                        svia_wd_fix(pdev);
                        hpriv->wd_workaround = true;
                        ap->link.eh_context.i.flags |= ATA_EHI_QUIET;
                }
        }

        ata_sff_error_handler(ap);
}

static void svia_configure(struct pci_dev *pdev, int board_id,
                           struct svia_priv *hpriv)
{
        u8 tmp8;

        pci_read_config_byte(pdev, PCI_INTERRUPT_LINE, &tmp8);
        dev_info(&pdev->dev, "routed to hard irq line %d\n",
                 (int) (tmp8 & 0xf0) == 0xf0 ? 0 : tmp8 & 0x0f);

        /* make sure SATA channels are enabled */
        pci_read_config_byte(pdev, SATA_CHAN_ENAB, &tmp8);
        if ((tmp8 & ALL_PORTS) != ALL_PORTS) {
                dev_dbg(&pdev->dev, "enabling SATA channels (0x%x)\n",
                        (int)tmp8);
                tmp8 |= ALL_PORTS;
                pci_write_config_byte(pdev, SATA_CHAN_ENAB, tmp8);
        }

        /* make sure interrupts for each channel sent to us */
        pci_read_config_byte(pdev, SATA_INT_GATE, &tmp8);
        if ((tmp8 & ALL_PORTS) != ALL_PORTS) {
                dev_dbg(&pdev->dev, "enabling SATA channel interrupts (0x%x)\n",
                        (int) tmp8);
                tmp8 |= ALL_PORTS;
                pci_write_config_byte(pdev, SATA_INT_GATE, tmp8);
        }

        /* make sure native mode is enabled */
        pci_read_config_byte(pdev, SATA_NATIVE_MODE, &tmp8);
        if ((tmp8 & NATIVE_MODE_ALL) != NATIVE_MODE_ALL) {
                dev_dbg(&pdev->dev,
                        "enabling SATA channel native mode (0x%x)\n",
                        (int) tmp8);
                tmp8 |= NATIVE_MODE_ALL;
                pci_write_config_byte(pdev, SATA_NATIVE_MODE, tmp8);
        }

        if ((board_id == vt6420 && vt6420_hotplug) || board_id == vt6421) {
                /* enable IRQ on hotplug */
                pci_read_config_byte(pdev, SVIA_MISC_3, &tmp8);
                if ((tmp8 & SATA_HOTPLUG) != SATA_HOTPLUG) {
                        dev_dbg(&pdev->dev,
                                "enabling SATA hotplug (0x%x)\n",
                                (int) tmp8);
                        tmp8 |= SATA_HOTPLUG;
                        pci_write_config_byte(pdev, SVIA_MISC_3, tmp8);
                }
        }

        /*
         * vt6420/1 has problems talking to some drives.  The following
         * is the fix from Joseph Chan <JosephChan@via.com.tw>.
         *
         * When host issues HOLD, device may send up to 20DW of data
         * before acknowledging it with HOLDA and the host should be
         * able to buffer them in FIFO.  Unfortunately, some WD drives
         * send up to 40DW before acknowledging HOLD and, in the
         * default configuration, this ends up overflowing vt6421's
         * FIFO, making the controller abort the transaction with
         * R_ERR.
         *
         * Rx52[2] is the internal 128DW FIFO Flow control watermark
         * adjusting mechanism enable bit and the default value 0
         * means host will issue HOLD to device when the left FIFO
         * size goes below 32DW.  Setting it to 1 makes the watermark
         * 64DW.
         *
         * https://bugzilla.kernel.org/show_bug.cgi?id=15173
         * http://article.gmane.org/gmane.linux.ide/46352
         * http://thread.gmane.org/gmane.linux.kernel/1062139
         *
         * As the fix slows down data transfer, apply it only if the error
         * actually appears - see vt6421_error_handler()
         * Apply the fix always on vt6420 as we don't know if SCR_ERROR can be
         * read safely.
         */
        if (board_id == vt6420) {
                svia_wd_fix(pdev);
                hpriv->wd_workaround = true;
        }
}

static int svia_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
{
        unsigned int i;
        int rc;
        struct ata_host *host = NULL;
        int board_id = (int) ent->driver_data;
        const unsigned *bar_sizes;
        struct svia_priv *hpriv;

        ata_print_version_once(&pdev->dev, DRV_VERSION);

        rc = pcim_enable_device(pdev);
        if (rc)
                return rc;

        if (board_id == vt6421)
                bar_sizes = &vt6421_bar_sizes[0];
        else
                bar_sizes = &svia_bar_sizes[0];

        for (i = 0; i < ARRAY_SIZE(svia_bar_sizes); i++)
                if ((pci_resource_start(pdev, i) == 0) ||
                    (pci_resource_len(pdev, i) < bar_sizes[i])) {
                        dev_err(&pdev->dev,
                                "invalid PCI BAR %u (sz 0x%llx, val 0x%llx)\n",
                                i,
                                (unsigned long long)pci_resource_start(pdev, i),
                                (unsigned long long)pci_resource_len(pdev, i));
                        return -ENODEV;
                }

        switch (board_id) {
        case vt6420:
                rc = vt6420_prepare_host(pdev, &host);
                break;
        case vt6421:
                rc = vt6421_prepare_host(pdev, &host);
                break;
        case vt8251:
                rc = vt8251_prepare_host(pdev, &host);
                break;
        default:
                rc = -EINVAL;
        }
        if (rc)
                return rc;

        hpriv = devm_kzalloc(&pdev->dev, sizeof(*hpriv), GFP_KERNEL);
        if (!hpriv)
                return -ENOMEM;
        host->private_data = hpriv;

        svia_configure(pdev, board_id, hpriv);

        pci_set_master(pdev);
        if ((board_id == vt6420 && vt6420_hotplug) || board_id == vt6421)
                return ata_host_activate(host, pdev->irq, vt642x_interrupt,
                                         IRQF_SHARED, &svia_sht);
        else
                return ata_host_activate(host, pdev->irq, ata_bmdma_interrupt,
                                         IRQF_SHARED, &svia_sht);
}

#ifdef CONFIG_PM_SLEEP
static int svia_pci_device_resume(struct pci_dev *pdev)
{
        struct ata_host *host = pci_get_drvdata(pdev);
        struct svia_priv *hpriv = host->private_data;
        int rc;

        rc = ata_pci_device_do_resume(pdev);
        if (rc)
                return rc;

        if (hpriv->wd_workaround)
                svia_wd_fix(pdev);
        ata_host_resume(host);

        return 0;
}
#endif

module_pci_driver(svia_pci_driver);