[libata] sata_mv: Enable use of (basic) DMA for ATAPI on GEN_IIE chips

This also gets rid of any need for mv_mode_filter().

Using basic DMA on GEN_IIE requires setting an undocumented
bit in an undocumented register.  For safety, we clear that
bit again when switching back to EDMA mode.

To avoid a performance penalty when switching modes,
we cache the register in port_priv, as already done for other regs.

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 28 insertions, 24 deletions

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index 146b8e67c44f..3bfe721ba766 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -345,7 +345,7 @@ enum {
         EDMA_ARB_CFG_OFS        = 0x38,
 
         EDMA_HALTCOND_OFS       = 0x60,         /* GenIIe halt conditions */
-
+        EDMA_UNKNOWN_RSVD_OFS   = 0x6C,         /* GenIIe unknown/reserved */
 
         BMDMA_CMD_OFS           = 0x224,        /* bmdma command register */
         BMDMA_STATUS_OFS        = 0x228,        /* bmdma status register */
@@ -447,6 +447,7 @@ struct mv_cached_regs {
         u32                     fiscfg;
         u32                     ltmode;
         u32                     haltcond;
+        u32                     unknown_rsvd;
 };
 
 struct mv_port_priv {
@@ -563,8 +564,6 @@ static void mv_pmp_error_handler(struct ata_port *ap);
 static void mv_process_crpb_entries(struct ata_port *ap,
                                         struct mv_port_priv *pp);
 
-static unsigned long mv_mode_filter(struct ata_device *dev,
-                                    unsigned long xfer_mask);
 static void mv_sff_irq_clear(struct ata_port *ap);
 static int mv_check_atapi_dma(struct ata_queued_cmd *qc);
 static void mv_bmdma_setup(struct ata_queued_cmd *qc);
@@ -626,7 +625,6 @@ static struct ata_port_operations mv6_ops = {
         .bmdma_start            = mv_bmdma_start,
         .bmdma_stop             = mv_bmdma_stop,
         .bmdma_status           = mv_bmdma_status,
-        .mode_filter            = mv_mode_filter,
 };
 
 static struct ata_port_operations mv_iie_ops = {
@@ -842,6 +840,7 @@ static void mv_save_cached_regs(struct ata_port *ap)
         pp->cached.fiscfg = readl(port_mmio + FISCFG_OFS);
         pp->cached.ltmode = readl(port_mmio + LTMODE_OFS);
         pp->cached.haltcond = readl(port_mmio + EDMA_HALTCOND_OFS);
+        pp->cached.unknown_rsvd = readl(port_mmio + EDMA_UNKNOWN_RSVD_OFS);
 }
 
 /**
@@ -1252,6 +1251,30 @@ static void mv_60x1_errata_sata25(struct ata_port *ap, int want_ncq)
                 writel(new, hpriv->base + MV_GPIO_PORT_CTL_OFS);
 }
 
+/**
+ *      mv_bmdma_enable - set a magic bit on GEN_IIE to allow bmdma
+ *      @ap: Port being initialized
+ *
+ *      There are two DMA modes on these chips:  basic DMA, and EDMA.
+ *
+ *      Bit-0 of the "EDMA RESERVED" register enables/disables use
+ *      of basic DMA on the GEN_IIE versions of the chips.
+ *
+ *      This bit survives EDMA resets, and must be set for basic DMA
+ *      to function, and should be cleared when EDMA is active.
+ */
+static void mv_bmdma_enable_iie(struct ata_port *ap, int enable_bmdma)
+{
+        struct mv_port_priv *pp = ap->private_data;
+        u32 new, *old = &pp->cached.unknown_rsvd;
+
+        if (enable_bmdma)
+                new = *old | 1;
+        else
+                new = *old & ~1;
+        mv_write_cached_reg(mv_ap_base(ap) + EDMA_UNKNOWN_RSVD_OFS, old, new);
+}
+
 static void mv_edma_cfg(struct ata_port *ap, int want_ncq, int want_edma)
 {
         u32 cfg;
@@ -1297,6 +1320,7 @@ static void mv_edma_cfg(struct ata_port *ap, int want_ncq, int want_edma)
                 }
                 if (hpriv->hp_flags & MV_HP_CUT_THROUGH)
                         cfg |= (1 << 17); /* enab cut-thru (dis stor&forwrd) */
+                mv_bmdma_enable_iie(ap, !want_edma);
         }
 
         if (want_ncq) {
@@ -1465,26 +1489,6 @@ static void mv_crqb_pack_cmd(__le16 *cmdw, u8 data, u8 addr, unsigned last)
 }
 
 /**
- *      mv_mode_filter - Allow ATAPI DMA only on GenII chips.
- *      @dev: device whose xfer modes are being configured.
- *
- *      Only the GenII hardware can use DMA with ATAPI drives.
- */
-static unsigned long mv_mode_filter(struct ata_device *adev,
-                                    unsigned long xfer_mask)
-{
-        if (adev->class == ATA_DEV_ATAPI) {
-                struct mv_host_priv *hpriv = adev->link->ap->host->private_data;
-                if (!IS_GEN_II(hpriv)) {
-                        xfer_mask &= ~(ATA_MASK_MWDMA | ATA_MASK_UDMA);
-                        ata_dev_printk(adev, KERN_INFO,
-                                "ATAPI DMA not supported on this chipset\n");
-                }
-        }
-        return xfer_mask;
-}
-
-/**
  *      mv_sff_irq_clear - Clear hardware interrupt after DMA.
  *      @ap: Port associated with this ATA transaction.
  *