linux-kernel - Re: [RFC PATCH] libata-sff: Fix oops reported in kerneloops.org for pnp devices with no ctl

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Date:	Thu, 29 May 2008 17:57:04 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org
Subject: Re: [RFC PATCH] libata-sff: Fix oops reported in kerneloops.org for
 pnp devices with no ctl

Alan Cox wrote:
> The Linusified version:
> 
> - Make ata_sff_altstatus private so nobody uses it by mistake
> - Drop the 400nS delay from it
> 
> Add
> 
> ata_sff_irq_status	-	encapsulates the IRQ check logic
> 
> This function keeps the existing behaviour for altstatus using devices. I
> actually suspect the logic was wrong before the changes but -rc isn't the
> time to play with that
> 
> ata_sff_sync		-	ensure writes hit the device
> 
> Really we want an io* operation for 'is posted' eg ioisposted(ioaddr) so
> that we can fix the nasty delay this causes on most systems.
> 
> - ata_sff_pause		-	400nS delay
> 
> Ensure the command hit the device and delay 400nS
> 
> - ata_sff_dma_pause
>  
> Ensure the I/O hit the device and enforce an HDMA1:0 transition delay.
> Requires altstatus register exists, BUG if not so we don't risk
> corruption in MWDMA modes. (UDMA the checksum will save your backside in
> theory)
> 
> The only other complication then is devices with their own handlers.
> rb532 can use dma_pause but scc needs to access its own altstatus
> register for internal errata workarounds so directly call the drivers own
> altstatus function.
> 
> Signed-off-by: Alan Cox <alan@...hat.com>

Honestly I think your first RFC PATCH (dated Thu, 29 May 2008 22:10:58 
+0100) turned out better than this.

NO_ALTSTATUS is a bit ugly, don't you think?

In any case, based on a quick review I would certainly ack the first RFC 
PATCH.

	Jeff




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