2 files changed, 140 insertions, 4 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 3acf56200d8..63488673765 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -65,6 +65,7 @@ static unsigned int ata_dev_init_params(struct ata_port *ap,
                                         struct ata_device *dev,
                                         u16 heads,
                                         u16 sectors);
+static int ata_down_sata_spd_limit(struct ata_port *ap);
 static int ata_set_mode(struct ata_port *ap, struct ata_device **r_failed_dev);
 static unsigned int ata_dev_set_xfermode(struct ata_port *ap,
                                          struct ata_device *dev);
@@ -1596,6 +1597,120 @@ void ata_port_disable(struct ata_port *ap)
         ap->flags |= ATA_FLAG_PORT_DISABLED;
 }
 
+/**
+ *      ata_down_sata_spd_limit - adjust SATA spd limit downward
+ *      @ap: Port to adjust SATA spd limit for
+ *
+ *      Adjust SATA spd limit of @ap downward.  Note that this
+ *      function only adjusts the limit.  The change must be applied
+ *      using ata_set_sata_spd().
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ *      RETURNS:
+ *      0 on success, negative errno on failure
+ */
+static int ata_down_sata_spd_limit(struct ata_port *ap)
+{
+        u32 spd, mask;
+        int highbit;
+
+        if (ap->cbl != ATA_CBL_SATA || !ap->ops->scr_read)
+                return -EOPNOTSUPP;
+
+        mask = ap->sata_spd_limit;
+        if (mask <= 1)
+                return -EINVAL;
+        highbit = fls(mask) - 1;
+        mask &= ~(1 << highbit);
+
+        spd = (scr_read(ap, SCR_STATUS) >> 4) & 0xf;
+        if (spd <= 1)
+                return -EINVAL;
+        spd--;
+        mask &= (1 << spd) - 1;
+        if (!mask)
+                return -EINVAL;
+
+        ap->sata_spd_limit = mask;
+
+        printk(KERN_WARNING "ata%u: limiting SATA link speed to %s\n",
+               ap->id, sata_spd_string(fls(mask)));
+
+        return 0;
+}
+
+static int __ata_set_sata_spd_needed(struct ata_port *ap, u32 *scontrol)
+{
+        u32 spd, limit;
+
+        if (ap->sata_spd_limit == UINT_MAX)
+                limit = 0;
+        else
+                limit = fls(ap->sata_spd_limit);
+
+        spd = (*scontrol >> 4) & 0xf;
+        *scontrol = (*scontrol & ~0xf0) | ((limit & 0xf) << 4);
+
+        return spd != limit;
+}
+
+/**
+ *      ata_set_sata_spd_needed - is SATA spd configuration needed
+ *      @ap: Port in question
+ *
+ *      Test whether the spd limit in SControl matches
+ *      @ap->sata_spd_limit.  This function is used to determine
+ *      whether hardreset is necessary to apply SATA spd
+ *      configuration.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ *      RETURNS:
+ *      1 if SATA spd configuration is needed, 0 otherwise.
+ */
+static int ata_set_sata_spd_needed(struct ata_port *ap)
+{
+        u32 scontrol;
+
+        if (ap->cbl != ATA_CBL_SATA || !ap->ops->scr_read)
+                return 0;
+
+        scontrol = scr_read(ap, SCR_CONTROL);
+
+        return __ata_set_sata_spd_needed(ap, &scontrol);
+}
+
+/**
+ *      ata_set_sata_spd - set SATA spd according to spd limit
+ *      @ap: Port to set SATA spd for
+ *
+ *      Set SATA spd of @ap according to sata_spd_limit.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ *      RETURNS:
+ *      0 if spd doesn't need to be changed, 1 if spd has been
+ *      changed.  -EOPNOTSUPP if SCR registers are inaccessible.
+ */
+static int ata_set_sata_spd(struct ata_port *ap)
+{
+        u32 scontrol;
+
+        if (ap->cbl != ATA_CBL_SATA || !ap->ops->scr_read)
+                return -EOPNOTSUPP;
+
+        scontrol = scr_read(ap, SCR_CONTROL);
+        if (!__ata_set_sata_spd_needed(ap, &scontrol))
+                return 0;
+
+        scr_write(ap, SCR_CONTROL, scontrol);
+        return 1;
+}
+
 /*
  * This mode timing computation functionality is ported over from
  * drivers/ide/ide-timing.h and was originally written by Vojtech Pavlik
@@ -2165,7 +2280,14 @@ static int sata_phy_resume(struct ata_port *ap)
 void ata_std_probeinit(struct ata_port *ap)
 {
         if ((ap->flags & ATA_FLAG_SATA) && ap->ops->scr_read) {
+                u32 spd;
+
                 sata_phy_resume(ap);
+
+                spd = (scr_read(ap, SCR_CONTROL) & 0xf0) >> 4;
+                if (spd)
+                        ap->sata_spd_limit &= (1 << spd) - 1;
+
                 if (sata_dev_present(ap))
                         ata_busy_sleep(ap, ATA_TMOUT_BOOT_QUICK, ATA_TMOUT_BOOT);
         }
@@ -2253,18 +2375,30 @@ int sata_std_hardreset(struct ata_port *ap, int verbose, unsigned int *class)
 
         DPRINTK("ENTER\n");
 
-        /* Issue phy wake/reset */
+        if (ata_set_sata_spd_needed(ap)) {
+                /* SATA spec says nothing about how to reconfigure
+                 * spd.  To be on the safe side, turn off phy during
+                 * reconfiguration.  This works for at least ICH7 AHCI
+                 * and Sil3124.
+                 */
+                scontrol = scr_read(ap, SCR_CONTROL);
+                scontrol = (scontrol & 0x0f0) | 0x302;
+                scr_write_flush(ap, SCR_CONTROL, scontrol);
+
+                ata_set_sata_spd(ap);
+        }
+
+        /* issue phy wake/reset */
         scontrol = scr_read(ap, SCR_CONTROL);
         scontrol = (scontrol & 0x0f0) | 0x301;
         scr_write_flush(ap, SCR_CONTROL, scontrol);
 
-        /*
-         * Couldn't find anything in SATA I/II specs, but AHCI-1.1
+        /* Couldn't find anything in SATA I/II specs, but AHCI-1.1
          * 10.4.2 says at least 1 ms.
          */
         msleep(1);
 
-        /* Bring phy back */
+        /* bring phy back */
         sata_phy_resume(ap);
 
         /* TODO: phy layer with polling, timeouts, etc. */
@@ -4454,6 +4588,7 @@ static void ata_host_init(struct ata_port *ap, struct Scsi_Host *host,
         ap->flags |= ent->host_flags;
         ap->ops = ent->port_ops;
         ap->cbl = ATA_CBL_NONE;
+        ap->sata_spd_limit = UINT_MAX;
         ap->active_tag = ATA_TAG_POISON;
         ap->last_ctl = 0xFF;
 
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 0f8e3720edd..a5207e66ca5 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -397,6 +397,7 @@ struct ata_port {
         unsigned int            mwdma_mask;
         unsigned int            udma_mask;
         unsigned int            cbl;    /* cable type; ATA_CBL_xxx */
+        unsigned int            sata_spd_limit; /* SATA PHY speed limit */
 
         struct ata_device       device[ATA_MAX_DEVICES];