[PATCH #upstream-fixes] libata: skip 0xff polling for PATA controllers

[PATCH #upstream-fixes] libata: skip 0xff polling for PATA controllers

[Tejun Heo]

In a presentation of true workmanship, pata_ali asserts IRQ
permanantly if the TF status register is read more than once when
there's no device attached to the port.

Avoid waiting polling for !0xff if it's PATA.  It's needed only for
some rare SATA devices anyway.

This problem is reported by Luca Tettamanti in bugzilla bug 9298.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Tested-By: Luca Tettamanti <kronos.it@gmail.com>
---
 drivers/ata/libata-core.c |   16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 009bd60..fd73f0b 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3383,14 +3383,20 @@ void ata_wait_after_reset(struct ata_port *ap, unsigned long deadline)
 	 * to clear 0xff after reset.  For example, HHD424020F7SV00
 	 * iVDR needs >= 800ms while.  Quantum GoVault needs even more
 	 * than that.
+	 *
+	 * Note that some PATA controllers (pata_ali) explode if
+	 * status register is read more than once when there's no
+	 * device attached.
 	 */
-	while (1) {
-		u8 status = ata_chk_status(ap);
+	if (ap->flags & ATA_FLAG_SATA) {
+		while (1) {
+			u8 status = ata_chk_status(ap);
 
-		if (status != 0xff || time_after(jiffies, deadline))
-			return;
+			if (status != 0xff || time_after(jiffies, deadline))
+				return;
 
-		msleep(50);
+			msleep(50);
+		}
 	}
 }
 

Re: [PATCH #upstream-fixes] libata: skip 0xff polling for PATA controllers

[Alan Cox]

On Thu, 08 Nov 2007 11:20:18 +0900
Tejun Heo <htejun@gmail.com> wrote:

> In a presentation of true workmanship, pata_ali asserts IRQ
> permanantly if the TF status register is read more than once when
> there's no device attached to the port.
> 
> Avoid waiting polling for !0xff if it's PATA.  It's needed only for
> some rare SATA devices anyway.
> 
> This problem is reported by Luca Tettamanti in bugzilla bug 9298.
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>
> Tested-By: Luca Tettamanti <kronos.it@gmail.com>
> ---
>  drivers/ata/libata-core.c |   16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)

Bletch.. 8)

Acked-by: Alan Cox <alan@redhat.com>

Re: [PATCH #upstream-fixes] libata: skip 0xff polling for PATA controllers

[Mark Lord]

Tejun Heo wrote:
> In a presentation of true workmanship, pata_ali asserts IRQ
> permanantly if the TF status register is read more than once when
> there's no device attached to the port.
..

Is using the altstatus reg (rather than status reg), when possible,
a better idea here?

Re: [PATCH #upstream-fixes] libata: skip 0xff polling for PATA controllers

[Tejun Heo]

Mark Lord wrote:
> Tejun Heo wrote:
>> In a presentation of true workmanship, pata_ali asserts IRQ
>> permanantly if the TF status register is read more than once when
>> there's no device attached to the port.
> ..
> 
> Is using the altstatus reg (rather than status reg), when possible,
> a better idea here?

I dunno.  It probably differs case-by-case.  In general, status reg
should be safer as it is supposed to clear IRQ.

-- 
tejun

Re: [PATCH #upstream-fixes] libata: skip 0xff polling for PATA controllers

[Jeff Garzik]

On Thu, Nov 08, 2007 at 11:20:18AM +0900, Tejun Heo wrote:
> In a presentation of true workmanship, pata_ali asserts IRQ
> permanantly if the TF status register is read more than once when
> there's no device attached to the port.
> 
> Avoid waiting polling for !0xff if it's PATA.  It's needed only for
> some rare SATA devices anyway.
> 
> This problem is reported by Luca Tettamanti in bugzilla bug 9298.
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>
> Tested-By: Luca Tettamanti <kronos.it@gmail.com>

applied