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Subject[PATCH] 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>
---
Okay, here it is. Sorry for the delay.
drivers/ata/libata-core.c | 32 +++++++++++++++++++-------------
1 file changed, 19 insertions(+), 13 deletions(-)
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 4733f00..02a44ff 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3059,22 +3059,28 @@ 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)
-
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