[PATCH] driver/FSL SATA:Fix wrong Device Error Register usage

[PATCH] driver/FSL SATA:Fix wrong Device Error Register usage

[Prabhakar Kushwaha]

When a single device error is detected, the device under the error is indicated
by the error bit set in the DER. There is a one to one mapping between register
bit and devices on Port multiplier(PMP) i.e. bit 0 represents PMP device 0 and
bit 1 represents PMP device 1 etc.

Current implementation treats Device error register value as device number not
set of bits representing multiple device on PMP. It is changed to consider bit
level.
No need to check for each set bit as all command is going to be aborted.

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Signed-off-by: Ashish Kalra <B00888@freescale.com>
---
 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git (branch master)

 This patch is already gone through review of linuxppc-dev mail list.
 Making CC linuxppc-dev@lists.ozlabs.org

 drivers/ata/sata_fsl.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/sata_fsl.c b/drivers/ata/sata_fsl.c
index b0214d0..895771c 100644
--- a/drivers/ata/sata_fsl.c
+++ b/drivers/ata/sata_fsl.c
@@ -1040,12 +1040,14 @@ static void sata_fsl_error_intr(struct ata_port *ap)
 
 		/* find out the offending link and qc */
 		if (ap->nr_pmp_links) {
+			unsigned int dev_num;
 			dereg = ioread32(hcr_base + DE);
 			iowrite32(dereg, hcr_base + DE);
 			iowrite32(cereg, hcr_base + CE);
 
-			if (dereg < ap->nr_pmp_links) {
-				link = &ap->pmp_link[dereg];
+			dev_num = ffs(dereg)-1;
+			if (dev_num < ap->nr_pmp_links) {
+				link = &ap->pmp_link[dev_num];
 				ehi = &link->eh_info;
 				qc = ata_qc_from_tag(ap, link->active_tag);
 				/*
-- 
1.7.3

RE: [PATCH] driver/FSL SATA:Fix wrong Device Error Register usage

[Kushwaha Prabhakar-B32579]

Thanks David for review comments!!

Please find my reply in-lined

> -----Original Message-----
> From: David Laight [mailto:David.Laight@ACULAB.COM]
> Sent: Friday, February 18, 2011 2:12 PM
> To: Kushwaha Prabhakar-B32579; linuxppc-dev@lists.ozlabs.org
> Cc: Kalra Ashish-B00888
> Subject: RE: [PATCH] driver/FSL SATA:Fix wrong Device Error Register=20
> usage
>=20
>=20
> > +			if ((ffs(dereg)-1) < ap->nr_pmp_links) {
> > +				/* array start from 0 */
> > +				link =3D &ap->pmp_link[ffs(dereg)-1];
>=20
> I'd only call ffs() once - it could be a slow library function.

This function is called during error handling. So it won't matter.=20
Anyway, I will update the patch for singe usage of ffs().=20

> Any comment should note that ffs() returns 0 when no bits are set -=20
> rather than anything about array indexes.
>=20
sata_fsl_error_intr() is called during device error.
The mentioned scenario will never comes. It can be observed via code:-
	if (cereg) {   --> cereg is set on command error. Means there is at least =
1 device present.
		abort =3D 1;
		---
		---
		---
		/* find out the offending link and qc */
		if (ap->nr_pmp_links) {  --> if Port multiplier=20
			---
			---
			if ((ffs(dereg)-1) < ap->nr_pmp_links) {
		---
		---
		} else {  -->  Single device
			dereg =3D ioread32(hcr_base + DE);
			iowrite32(dereg, hcr_base + DE);
			iowrite32(cereg, hcr_base + CE);

RE: [PATCH] driver/FSL SATA:Fix wrong Device Error Register usage

[Kushwaha Prabhakar-B32579]

Thanks David for review comments!!

Please find my reply in-lined

> -----Original Message-----
> From: David Laight [mailto:David.Laight@ACULAB.COM]
> Sent: Friday, February 18, 2011 2:12 PM
> To: Kushwaha Prabhakar-B32579; linuxppc-dev@lists.ozlabs.org
> Cc: Kalra Ashish-B00888
> Subject: RE: [PATCH] driver/FSL SATA:Fix wrong Device Error Register
> usage
>=20
>=20
> > +			if ((ffs(dereg)-1) < ap->nr_pmp_links) {
> > +				/* array start from 0 */
> > +				link =3D &ap->pmp_link[ffs(dereg)-1];
>=20
> I'd only call ffs() once - it could be a slow library function.

This function is called during error handling. So it won't matter.=20
Anyway, I will update the patch for singe usage of ffs().=20

> Any comment should note that ffs() returns 0 when no bits are set -
> rather than anything about array indexes.
>=20
sata_fsl_error_intr() is called during device error.
The mentioned scenario will never comes. It can be observed via code:-
	if (cereg) {   --> cereg is set on command error. Means there is at least =
1 device present.
		abort =3D 1;
		---
		---
		---
		/* find out the offending link and qc */
		if (ap->nr_pmp_links) {  --> if Port multiplier=20
			---
			---
			if ((ffs(dereg)-1) < ap->nr_pmp_links) {
		---
		---
		} else {  -->  Single device
			dereg =3D ioread32(hcr_base + DE);
			iowrite32(dereg, hcr_base + DE);
			iowrite32(cereg, hcr_base + CE);

RE: [PATCH] driver/FSL SATA:Fix wrong Device Error Register usage

[David Laight]

=20
> +			if ((ffs(dereg)-1) < ap->nr_pmp_links) {
> +				/* array start from 0 */
> +				link =3D &ap->pmp_link[ffs(dereg)-1];

I'd only call ffs() once - it could be a slow library function.
Any comment should note that ffs() returns 0 when no bits
are set - rather than anything about array indexes.

	David

[PATCH] driver/FSL SATA:Fix wrong Device Error Register usage

[Prabhakar Kushwaha]

When a single device error is detected, the device under the error is indicated
by the error bit set in the DER. There is a one to one mapping between register
bit and devices on Port multiplier(PMP) i.e. bit 0 represents PMP device 0 and
bit 1 represents PMP device 1 etc.

Current implementation treats Device error register value as device number not
set of bits representing multiple device on PMP. It is changed to consider bit
level.
No need to check for each set bit as all command is going to be aborted.

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Signed-off-by: Ashish Kalra <B00888@freescale.com>
---
 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git (branch master)

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

diff --git a/drivers/ata/sata_fsl.c b/drivers/ata/sata_fsl.c
index 2546f38..8ad335f 100644
--- a/drivers/ata/sata_fsl.c
+++ b/drivers/ata/sata_fsl.c
@@ -1047,8 +1047,9 @@ static void sata_fsl_error_intr(struct ata_port *ap)
 			iowrite32(dereg, hcr_base + DE);
 			iowrite32(cereg, hcr_base + CE);
 
-			if (dereg < ap->nr_pmp_links) {
-				link = &ap->pmp_link[dereg];
+			if ((ffs(dereg)-1) < ap->nr_pmp_links) {
+				/* array start from 0 */
+				link = &ap->pmp_link[ffs(dereg)-1];
 				ehi = &link->eh_info;
 				qc = ata_qc_from_tag(ap, link->active_tag);
 				/*
-- 
1.7.3