sata_mv: workaround errata SATA#26

Workaround for errata SATA#26.

Prevents accidently putting a drive to sleep when attempting COMRESET,
by ORing 0xf000 with the values written to SCR_CONTROL.

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

1 files changed, 19 insertions, 1 deletions

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index b0c929d36234..d689fb9ceb96 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -1296,7 +1296,25 @@ static int mv_scr_write(struct ata_link *link, unsigned int sc_reg_in, u32 val)
         unsigned int ofs = mv_scr_offset(sc_reg_in);
 
         if (ofs != 0xffffffffU) {
-                writelfl(val, mv_ap_base(link->ap) + ofs);
+                void __iomem *addr = mv_ap_base(link->ap) + ofs;
+                if (sc_reg_in == SCR_CONTROL) {
+                        /*
+                         * Workaround for 88SX60x1 FEr SATA#26:
+                         *
+                         * COMRESETs have to take care not to accidently
+                         * put the drive to sleep when writing SCR_CONTROL.
+                         * Setting bits 12..15 prevents this problem.
+                         *
+                         * So if we see an outbound COMMRESET, set those bits.
+                         * Ditto for the followup write that clears the reset.
+                         *
+                         * The proprietary driver does this for
+                         * all chip versions, and so do we.
+                         */
+                        if ((val & 0xf) == 1 || (readl(addr) & 0xf) == 1)
+                                val |= 0xf000;
+                }
+                writelfl(val, addr);
                 return 0;
         } else
                 return -EINVAL;