libata: limit post SRST nsect/lbal wait to ~100ms

After SRST, libata used to wait for nsect/lbal to be set to 1/1 for
the slave device.  However, some ATAPI devices don't set nsect/lbal
after SRST and the wait itself isn't too useful as we're gonna wait
for !BSY right after that anyway.

Before reset-seq update, nsect/lbal wait failure used to be ignored
and caused 30sec delay during detection.  After reset-seq, all
timeouts are considered error conditions making libata fail to detect
such ATAPI devices.

This patch limits nsect/lbal wait to around 100ms.  This should give
acceptable behavior to such ATAPI devices while not disturbing the
heavily used code path too much.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 19 insertions, 13 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 76aa94f55af..047eabd7536 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3061,22 +3061,28 @@ static int ata_bus_post_reset(struct ata_port *ap, unsigned int devmask,
                 }
         }
 
-        /* if device 1 was found in ata_devchk, wait for
-         * register access, then wait for BSY to clear
+        /* if device 1 was found in ata_devchk, wait for register
+         * access briefly, then wait for BSY to clear.
          */
-        while (dev1) {
-                u8 nsect, lbal;
+        if (dev1) {
+                int i;
 
                 ap->ops->dev_select(ap, 1);
-                nsect = ioread8(ioaddr->nsect_addr);
-                lbal = ioread8(ioaddr->lbal_addr);
-                if ((nsect == 1) && (lbal == 1))
-                        break;
-                if (time_after(jiffies, deadline))
-                        return -EBUSY;
-                msleep(50);     /* give drive a breather */
-        }
-        if (dev1) {
+
+                /* Wait for register access.  Some ATAPI devices fail
+                 * to set nsect/lbal after reset, so don't waste too
+                 * much time on it.  We're gonna wait for !BSY anyway.
+                 */
+                for (i = 0; i < 2; i++) {
+                        u8 nsect, lbal;
+
+                        nsect = ioread8(ioaddr->nsect_addr);
+                        lbal = ioread8(ioaddr->lbal_addr);
+                        if ((nsect == 1) && (lbal == 1))
+                                break;
+                        msleep(50);     /* give drive a breather */
+                }
+
                 rc = ata_wait_ready(ap, deadline);
                 if (rc) {
                         if (rc != -ENODEV)