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>

1 files changed, 20 insertions, 5 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 564c03c4ebb..3c5965d56c4 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",