libata: add @spd_limit to sata_down_spd_limit()

Add @spd_limit to sata_down_spd_limit() so that the caller can specify
the SPD limit it wants.  This parameter doesn't get in the way even
when it's too low.  The closest possible limit is applied.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

4 files changed, 27 insertions, 12 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 564c03c4ebb3..3c5965d56c47 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -2777,7 +2777,7 @@ int ata_bus_probe(struct ata_port *ap)
                         /* This is the last chance, better to slow
                          * down than lose it.
                          */
-                        sata_down_spd_limit(&ap->link);
+                        sata_down_spd_limit(&ap->link, 0);
                         ata_down_xfermask_limit(dev, ATA_DNXFER_PIO);
                 }
         }
@@ -2873,21 +2873,27 @@ void ata_port_disable(struct ata_port *ap)
 /**
  *      sata_down_spd_limit - adjust SATA spd limit downward
  *      @link: Link to adjust SATA spd limit for
+ *      @spd_limit: Additional limit
  *
  *      Adjust SATA spd limit of @link downward.  Note that this
  *      function only adjusts the limit.  The change must be applied
  *      using sata_set_spd().
  *
+ *      If @spd_limit is non-zero, the speed is limited to equal to or
+ *      lower than @spd_limit if such speed is supported.  If
+ *      @spd_limit is slower than any supported speed, only the lowest
+ *      supported speed is allowed.
+ *
  *      LOCKING:
  *      Inherited from caller.
  *
  *      RETURNS:
  *      0 on success, negative errno on failure
  */
-int sata_down_spd_limit(struct ata_link *link)
+int sata_down_spd_limit(struct ata_link *link, u32 spd_limit)
 {
         u32 sstatus, spd, mask;
-        int rc, highbit;
+        int rc, bit;
 
         if (!sata_scr_valid(link))
                 return -EOPNOTSUPP;
@@ -2906,8 +2912,8 @@ int sata_down_spd_limit(struct ata_link *link)
                 return -EINVAL;
 
         /* unconditionally mask off the highest bit */
-        highbit = fls(mask) - 1;
-        mask &= ~(1 << highbit);
+        bit = fls(mask) - 1;
+        mask &= ~(1 << bit);
 
         /* Mask off all speeds higher than or equal to the current
          * one.  Force 1.5Gbps if current SPD is not available.
@@ -2921,6 +2927,15 @@ int sata_down_spd_limit(struct ata_link *link)
         if (!mask)
                 return -EINVAL;
 
+        if (spd_limit) {
+                if (mask & ((1 << spd_limit) - 1))
+                        mask &= (1 << spd_limit) - 1;
+                else {
+                        bit = ffs(mask) - 1;
+                        mask = 1 << bit;
+                }
+        }
+
         link->sata_spd_limit = mask;
 
         ata_link_printk(link, KERN_WARNING, "limiting SATA link speed to %s\n",
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 90092c1aae53..685509bc7ff0 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -1875,7 +1875,7 @@ static unsigned int ata_eh_speed_down(struct ata_device *dev,
         /* speed down? */
         if (verdict & ATA_EH_SPDN_SPEED_DOWN) {
                 /* speed down SATA link speed if possible */
-                if (sata_down_spd_limit(link) == 0) {
+                if (sata_down_spd_limit(link, 0) == 0) {
                         action |= ATA_EH_RESET;
                         goto done;
                 }
@@ -2627,11 +2627,11 @@ int ata_eh_reset(struct ata_link *link, int classify,
         }
 
         if (try == max_tries - 1) {
-                sata_down_spd_limit(link);
+                sata_down_spd_limit(link, 0);
                 if (slave)
-                        sata_down_spd_limit(slave);
+                        sata_down_spd_limit(slave, 0);
         } else if (rc == -EPIPE)
-                sata_down_spd_limit(failed_link);
+                sata_down_spd_limit(failed_link, 0);
 
         if (hardreset)
                 reset = hardreset;
@@ -3011,7 +3011,7 @@ static int ata_eh_handle_dev_fail(struct ata_device *dev, int err)
                         /* This is the last chance, better to slow
                          * down than lose it.
                          */
-                        sata_down_spd_limit(ata_dev_phys_link(dev));
+                        sata_down_spd_limit(ata_dev_phys_link(dev), 0);
                         if (dev->pio_mode > XFER_PIO_0)
                                 ata_down_xfermask_limit(dev, ATA_DNXFER_PIO);
                 }
diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
index 98ca07a2db87..619f2c33950e 100644
--- a/drivers/ata/libata-pmp.c
+++ b/drivers/ata/libata-pmp.c
@@ -729,7 +729,7 @@ static int sata_pmp_eh_recover_pmp(struct ata_port *ap,
                 if (tries) {
                         /* consecutive revalidation failures? speed down */
                         if (reval_failed)
-                                sata_down_spd_limit(link);
+                                sata_down_spd_limit(link, 0);
                         else
                                 reval_failed = 1;
 
diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
index 0a6f5be15112..cea8014cd87e 100644
--- a/drivers/ata/libata.h
+++ b/drivers/ata/libata.h
@@ -99,7 +99,7 @@ extern int ata_dev_reread_id(struct ata_device *dev, unsigned int readid_flags);
 extern int ata_dev_revalidate(struct ata_device *dev, unsigned int new_class,
                               unsigned int readid_flags);
 extern int ata_dev_configure(struct ata_device *dev);
-extern int sata_down_spd_limit(struct ata_link *link);
+extern int sata_down_spd_limit(struct ata_link *link, u32 spd_limit);
 extern int ata_down_xfermask_limit(struct ata_device *dev, unsigned int sel);
 extern void ata_sg_clean(struct ata_queued_cmd *qc);
 extern void ata_qc_free(struct ata_queued_cmd *qc);