[patch for 2.6.29? 3/4] pata_legacy: for VLB 32bit PIO don't try tricks with slop

[patch for 2.6.29? 3/4] pata_legacy: for VLB 32bit PIO don't try tricks with slop

[akpm]

From: Alan Cox <alan@lxorguk.ukuu.org.uk>

These devices are generally used with ATA anyway and it seems that some
ATAPI will need us to issue the right number of words.  Therefore as we
can't switch mid burst on VLB devices we should only use 32bit I/O for
suitable block sizes.


Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/ata/pata_legacy.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff -puN drivers/ata/pata_legacy.c~pata_legacy-for-vlb-32bit-pio-dont-try-tricks-with-slop drivers/ata/pata_legacy.c
--- a/drivers/ata/pata_legacy.c~pata_legacy-for-vlb-32bit-pio-dont-try-tricks-with-slop
+++ a/drivers/ata/pata_legacy.c
@@ -283,9 +283,10 @@ static void pdc20230_set_piomode(struct 
 static unsigned int pdc_data_xfer_vlb(struct ata_device *dev,
 			unsigned char *buf, unsigned int buflen, int rw)
 {
-	if (ata_id_has_dword_io(dev->id)) {
+	int slop = buflen & 3;
+	/* 32bit I/O capable *and* we need to write a whole number of dwords */
+	if (ata_id_has_dword_io(dev->id) && (slop == 0 || slop == 3)) {
 		struct ata_port *ap = dev->link->ap;
-		int slop = buflen & 3;
 		unsigned long flags;
 
 		local_irq_save(flags);
@@ -735,7 +736,7 @@ static unsigned int vlb32_data_xfer(stru
 	struct ata_port *ap = adev->link->ap;
 	int slop = buflen & 3;
 
-	if (ata_id_has_dword_io(adev->id)) {
+	if (ata_id_has_dword_io(adev->id) && (slop == 0 || slop == 3)) {
 		if (rw == WRITE)
 			iowrite32_rep(ap->ioaddr.data_addr, buf, buflen >> 2);
 		else
_

Re: [patch for 2.6.29? 3/4] pata_legacy: for VLB 32bit PIO don't try tricks with slop

[Jeff Garzik]

akpm@linux-foundation.org wrote:
> From: Alan Cox <alan@lxorguk.ukuu.org.uk>
> 
> These devices are generally used with ATA anyway and it seems that some
> ATAPI will need us to issue the right number of words.  Therefore as we
> can't switch mid burst on VLB devices we should only use 32bit I/O for
> suitable block sizes.
> 
> 
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Pinged Alan on 2/2, no response.

This was not signed-off-by by Alan, which is unlike him.  Also, there 
were no comments about testing.

So it seemed to me a test patch that I should hold onto, and waiting for 
Alan's and others' comments first.

	Jeff

Re: [patch for 2.6.29? 3/4] pata_legacy: for VLB 32bit PIO don't try tricks with slop

[Jeff Garzik]

akpm@linux-foundation.org wrote:
> From: Alan Cox <alan@lxorguk.ukuu.org.uk>
> 
> These devices are generally used with ATA anyway and it seems that some
> ATAPI will need us to issue the right number of words.  Therefore as we
> can't switch mid burst on VLB devices we should only use 32bit I/O for
> suitable block sizes.
> 
> 
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  drivers/ata/pata_legacy.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

applied

These two haven't much testing, but I can't in good conscience let them 
slip to 2.6.30 either...  Let's get them in.

	Jeff