linux-kernel - Re: [PATCH] pata_pdc202xx_old: Fix crashes with ATAPI

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Date:	Tue, 22 Jan 2008 00:13:53 +0100
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	jeff@...zik.org, akpm@...l.org, torvalds@...l.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pata_pdc202xx_old: Fix crashes with ATAPI


Hi,

On Saturday 19 January 2008, Alan Cox wrote:
> The PDC202xx older devices do not support ATAPI DMA via the usual
> interfaces. What documentation I have isn't sufficient to support DMA and
> it isn't clear if the Windows drivers do this or it is possible at all.
> (Neither do the drivers/ide old drivers)

IDE pdc202xx_old host driver supports ATAPI DMA just fine and in line
with the PDC2026x programming guide.

> So turn it ATAPI DMA off, these are disk optimised controllers.

This is an acceptable workaround for 2.6.24 but it probably just hides
some deeper pata_pdc202xx_old or/and libata problem.

Thanks,
Bart

> Signed-off-by: Alan Cox <alan@...hat.com>
> 
> diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.24-rc8-mm1/drivers/ata/pata_pdc202xx_old.c linux-2.6.24-rc8-mm1/drivers/ata/pata_pdc202xx_old.c
> --- linux.vanilla-2.6.24-rc8-mm1/drivers/ata/pata_pdc202xx_old.c	2008-01-19 14:47:56.000000000 +0000
> +++ linux-2.6.24-rc8-mm1/drivers/ata/pata_pdc202xx_old.c	2008-01-19 15:19:25.000000000 +0000
> @@ -243,6 +243,24 @@
>  	return ata_sff_port_start(ap);
>  }
>  
> +/**
> + *	pdc2026x_check_atapi_dma - Check whether ATAPI DMA can be supported for this command
> + *	@qc: Metadata associated with taskfile to check
> + *
> + *	Just say no - not supported on older Promise.
> + *
> + *	LOCKING:
> + *	None (inherited from caller).
> + *
> + *	RETURNS: 0 when ATAPI DMA can be used
> + *		 1 otherwise
> + */
> +
> +static int pdc2026x_check_atapi_dma(struct ata_queued_cmd *qc)
> +{
> +	return 1;
> +}
> +
>  static struct scsi_host_template pdc202xx_sht = {
>  	.module			= THIS_MODULE,
>  	.name			= DRV_NAME,
> @@ -310,6 +328,7 @@
>  	.post_internal_cmd = ata_bmdma_post_internal_cmd,
>  	.cable_detect	= pdc2026x_cable_detect,
>  
> +	.check_atapi_dma= pdc2026x_check_atapi_dma,
>  	.bmdma_setup 	= ata_bmdma_setup,
>  	.bmdma_start 	= pdc2026x_bmdma_start,
>  	.bmdma_stop	= pdc2026x_bmdma_stop,
--
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