Re: [PATCH] atiixp: missing parentheses?

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Tuesday 17 February 2009, Roel Kluin wrote:
> Bartlomiej Zolnierkiewicz wrote:
> > On Tuesday 17 February 2009, Sergei Shtylyov wrote:
> >> I wrote:
> >>
> >>>> This looks odd, is below what was intended? note that timing_shift can
> >>>> only be 16, 8 or 0. Maybe intended was 24, 16, 8 or 0? then we should do:
> >>>    Looking at the libata driver, yes, it should be 0, 8, 16, and 24.
> >>>> int timing_shift = ((drive->dn & 2) ? 16 : 0) + ((drive->dn & 1) ? 0 : 
> >>>> 8);
> 
> >>>    Why didn't you add parens around the first ?: then? They are surely 
> >>> needed.
> 
> I was unsure what was intended so I chose to keep semantics, but wanted to
> show the oddity. Thankfully you were able to clarify that it's a bug.
> 
> >>     Oh, actually, timing_shift = (drive->dn ^ 1) * 8.
> > 
> > Yes, this way we'll get the correct:
> > 
> > 8 0 24 16
> > 
> > instead of the current
> > 
> > 8 0 16 16
> 
> 
> > 
> > [ Luckily after DMA timings gets programmed for the third device to
> >   offset 16 they get overwritten with DMA timings for fourth device.
> > 
> >   Since BIOS should program DMA timings for the third device all
> >   should work fine till suspend/resume... ] 
> > 
> > Roel, please fix the patch and resubmit.
> > 
> > Thanks,
> > Bart
> I am not sure what to write for the changelog, so I kept your remarks.
> Feel free to change them if necessary.
> --------------------------->8-------------8<------------------------------
> DMA timings were incorrect. this way we'll get the correct:
> 
> 8 0 24 16 
> 
> instead of the current
> 
> 8 0 16 16
> 
> Luckily after DMA timings get programmed for the third device to
> offset 16 they get overwritten with DMA timings for fourth device.
> 
> Since BIOS should program DMA timings for the third device all
> should work fine till suspend/resume...
> 
> Signed-off-by: Roel Kluin <roel.kluin@gmail.com>

thanks, the applied version below:

From: Roel Kluin <roel.kluin@gmail.com>
Subject: [PATCH] atiixp: fix missing parentheses

Fix missing parentheses so PIO/DMA timings for master device on the
second channel are programmed correctly (IOW "8 0 24 16" offset values
should be used instead of the current "8 0 16 16").

[ The bug went unnoticed because after PIO/DMA timings get programmed
  incorrectly for the third device they are overwritten with timings
  for the fourth device and since BIOS should also program timings for
  the third device everything should work fine until suspend/resume
  cycle or user requested transfer mode changes. ]

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
[bart: update patch description]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
---
 drivers/ide/atiixp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: b/drivers/ide/atiixp.c
===================================================================
--- a/drivers/ide/atiixp.c
+++ b/drivers/ide/atiixp.c
@@ -52,7 +52,7 @@ static void atiixp_set_pio_mode(ide_driv
 {
 	struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
 	unsigned long flags;
-	int timing_shift = (drive->dn & 2) ? 16 : 0 + (drive->dn & 1) ? 0 : 8;
+	int timing_shift = (drive->dn ^ 1) * 8;
 	u32 pio_timing_data;
 	u16 pio_mode_data;
 
@@ -85,7 +85,7 @@ static void atiixp_set_dma_mode(ide_driv
 {
 	struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
 	unsigned long flags;
-	int timing_shift = (drive->dn & 2) ? 16 : 0 + (drive->dn & 1) ? 0 : 8;
+	int timing_shift = (drive->dn ^ 1) * 8;
 	u32 tmp32;
 	u16 tmp16;
 	u16 udma_ctl = 0;