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

[Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>]

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 */