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

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To: Patrick Wildi <patrick@wildi.com>
Date:	Thu, 29 Apr 2004 21:32:26 +0200

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.

> - 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). ;)

> 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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• Previous message: R. J. Wysocki: "2.6.6-rc3 broken on dual Opteron"
• In reply to: Patrick Wildi: "[RFC][PATCH] 2.4 IDE Serverworks OSB4 DMA patch"
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