Re: [RFC][PATCH] 2.4 IDE Serverworks OSB4 DMA patch

[Patrick Wildi <patrick@wildi.com>]

On Thu, 29 Apr 2004, Bartlomiej Zolnierkiewicz wrote:

> On Thursday 29 of April 2004 21:04, Patrick Wildi wrote:
> > I have been using a OSB4 chipset based system with a CompactFlash
> > that supports PIO only and a laptop IBM/Hitachi Travelstar HDD
> > that supports UDMA.
> > For both drives, the serverworks code misconfigures the drives:
> >
> > - for the CF (hooked up as /dev/hda), svwks_config_drive_xfer_rate()
> >   will not match any tests (drive->autodma = 0, id->capability = 2,
> >   id->field_valid = 1), but the function will then call
> >   hwif->ide_dma_on(drive), which it should not do for this drive.
> >   This patch moves the enabling of DMA up into the DMA section of
> >   the code.
>
> Yep, known bug, it is fixed in 2.6.
>
> It is present in many other drivers, my 2.6 patch needs to be backported.

Are you the maintainer for 2.4 or to whom should I send the changes?

> > - for the Travelstart HDD, the settings coming into
> >   svwks_config_drive_xfer_rate() are: drive->autodma = 32,
> >   id->capability = 15, id->field_valid = 7, id->dma_ultra = 0x43f.
> >   But as this is an OSB4, the hwif->ultra_mask is set to not support
> >   UDMA. Unfortunately in that case svwks_config_drive_xfer_rate()
> >   falls through to the end of the function, instead of trying
> >   other DMA modes.
>
> Good catch.
>
> It seems the same bug can be present in other drivers too (hint, hint). ;)

I noticed that the piix driver uses the exact same logic. I could
replicate this part of the patch for other 2.4 drivers. I have no
way of testing them.
I can send you a combined patch for 2.4. I am not yet using 2.6.

Patrick

> >   By adding a jump to try_dma_modes in the case that the drive
> >   is UDMA capable but the mask does not allow UDMA, the drive
> >   will be setup up for MWDMA.
> >
> > The logic in svwks_config_drive_xfer_rate() could probably be
> > improved a bit, but I kept the changes to an absolute minium
> > to reduce the risk of breakage.
>
> OK, thanks.
>
> > The patch is against 2.4.24, but the file has not changed in
> > 2.4.25 and 2.4.26.
> >
> > Patrick
> >
> >
> > --- linux-2.4.24-nam/drivers/ide/pci/serverworks.c.orig	Thu Apr 22 17:31:28
> > 2004 +++ linux-2.4.24-nam/drivers/ide/pci/serverworks.c	Thu Apr 29 11:02:05
> > 2004 @@ -473,7 +473,9 @@
> >  				int dma = config_chipset_for_dma(drive);
> >  				if ((id->field_valid & 2) && !dma)
> >  					goto try_dma_modes;
> > -			}
> > +			} else
> > +				/* UDMA disabled by mask, try other DMA modes */
> > +				goto try_dma_modes;
> >  		} else if (id->field_valid & 2) {
> >  try_dma_modes:
> >  			if ((id->dma_mword & hwif->mwdma_mask) ||
> > @@ -490,6 +492,7 @@
> >  		} else {
> >  			goto no_dma_set;
> >  		}
> > +		return hwif->ide_dma_on(drive);
> >  	} else if ((id->capability & 8) || (id->field_valid & 2)) {
> >  fast_ata_pio:
> >  no_dma_set:
> > @@ -497,7 +500,7 @@
> >  		//	hwif->tuneproc(drive, 5);
> >  		return hwif->ide_dma_off_quietly(drive);
> >  	}
> > -	return hwif->ide_dma_on(drive);
> > +	return 0;
> >  }
> >
> >  /* This can go soon */
>
> -
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