[PATCH] sata_nv: fix nmi intr or system hanging in rhel4u6 adma.

["Kuan Luo" <kluo@nvidia.com>]

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Hi, robert 

One customer reported that their system received a nmi interrupt after
issuing "dd if=/dev/sdb of=/dev/null" on a defective disk in rhel4u6.
I tested it and found  that my system hung both in rhel4u6(2.6.9-67) and
2.6.24-rc7.
The patch can work well,  but I am not sure if the patch has other
potential effect on adma.
I attached a  file in case of lines breaked.

The below info comes from Gunther Mayer to reproduce the issue.
"
used a Seagate ST3500841NS 3.AE for my test; probably other 
seagate drives are also capable of creating media errors with 
the new hdparm-8.1: 

- compile hdparm-8.1 
- hdparm -- yes-i-know-what-i-am-doing --make-bad-sector 60000 /dev/sdb 

Unfortunately this does not succeed for nvidia sata controller (timeouts
et al.), but it worked fine on AHCI machine (e.g. FSC R640). 

When I insert this newly created defective disk in Ultra 20, 
it reboots within seconds after issueing "dd if=/dev/sdb of=/dev/null". 
"

Signed-off-by: kluo@nvidia.com

---
 
drivers/ata/sata_nv.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/sata_nv.c b/drivers/ata/sata_nv.c
index ed5473b..e824260 100644
--- a/drivers/ata/sata_nv.c
+++ b/drivers/ata/sata_nv.c
@@ -837,9 +837,10 @@ static void nv_adma_tf_read(struct ata_port *ap,
struct ata_taskfile *tf)
 	   all shortly be aborted anyway. We assume that NCQ commands
are not
 	   issued via passthrough, which is the only way that switching
into
 	   ADMA mode could abort outstanding commands. */
-	nv_adma_register_mode(ap);
+	struct nv_adma_port_priv *pp = ap->private_data;
 
-	ata_tf_read(ap, tf);
+	if (pp->flags & NV_ADMA_PORT_REGISTER_MODE)
+		ata_tf_read(ap, tf);
 }
 
 static unsigned int nv_adma_tf_to_cpb(struct ata_taskfile *tf, __le16
*cpb)

-

Best regards,
Kuan Luo

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Signed-off-by: kluo@nvidia.com

 drivers/ata/sata_nv.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/sata_nv.c b/drivers/ata/sata_nv.c
index ed5473b..e824260 100644
--- a/drivers/ata/sata_nv.c
+++ b/drivers/ata/sata_nv.c
@@ -837,9 +837,10 @@ static void nv_adma_tf_read(struct ata_port *ap, struct ata_taskfile *tf)
 	   all shortly be aborted anyway. We assume that NCQ commands are not
 	   issued via passthrough, which is the only way that switching into
 	   ADMA mode could abort outstanding commands. */
-	nv_adma_register_mode(ap);
+	struct nv_adma_port_priv *pp = ap->private_data;
 
-	ata_tf_read(ap, tf);
+	if (pp->flags & NV_ADMA_PORT_REGISTER_MODE)
+		ata_tf_read(ap, tf);
 }
 
 static unsigned int nv_adma_tf_to_cpb(struct ata_taskfile *tf, __le16 *cpb)