linux-kernel - Re: SATA_SIL on IXP425 workaround

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Message-ID: <4B57DEE9.8030604@garzik.org>
Date:	Wed, 20 Jan 2010 23:58:17 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Krzysztof Halasa <khc@...waw.pl>
CC:	linux-ide@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: SATA_SIL on IXP425 workaround

On 01/14/2010 10:59 AM, Bartlomiej Zolnierkiewicz wrote:
> On Monday 09 November 2009 06:31:21 pm Krzysztof Halasa wrote:
>> I'm trying to add a workaround for IXP4xx CPUs to SATA SIL driver. The
>> problem is that IXP4xx CPUs (Intel's XScale (ARM) network-oriented
>> processors) are unable to perform 8 and 16-bit read from PCI MMIO, they
>> can only do a full 32-bit readl(); SIL chips respond to that with PCI
>> abort. The workaround is to use 8 and 16-bit regular IO reads (inb/inw)
>> instead (MMIO write is not a problem).
>>
>> For SIL3x12 the workaround is simple (attached) and it works on my 3512.
>> I'm not sure about 3114 (the 4-port chip) - the PIO BARs have TF, CTL
>> and BWDMA registers which are common to channels 0 and 2, and (the other
>> set) to channels 1 and 3. Channel selection is done with bit 4 of
>> device/head TF register, this is similar (same?) as PATA master/slave.
>> Does that mean that I can simply treat channel 0 as PRI master, ch#2 as
>> PRI slave, ch#1 as SEC master and ch#3 as SEC slave, and the SFF code
>> will select the right device correctly? Does it need additional code?
>> I don't have anything based on 3114.
>>
>> Note: the large PRD is not a problem here, the transfer can be started
>> by MMIO write. Only reads are an issue.
>
> FWIW your patch is now in my atang tree (I'm aware that Jeff is working
> on generic solution but in the meantime this non-intrusive patch allows
> sata_sil to work on IXP425).

I was asking an open question, is a generic solution possible?

Something like the attached patch might work, due it is completely 
untested, and I did not verify that the BMDMA Status register is not 
stomped.  Also, the additional ioread32() calls in bmdma start/stop are 
LIKELY to be unnecessary.

	Jeff





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