linux-kernel - Re: SATA_SIL: Add a work-around for IXP4xx CPU.

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Message-ID: <4B282C2A.4050801@kernel.org>
Date:	Wed, 16 Dec 2009 09:39:06 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Krzysztof Halasa <khc@...waw.pl>
CC:	Jeff Garzik <jgarzik@...ox.com>, linux-ide@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: SATA_SIL: Add a work-around for IXP4xx CPU.

Hello,

On 12/16/2009 08:03 AM, Krzysztof Halasa wrote:
> Tejun Heo <tj@...nel.org> writes:
> 
>> Hmmm... Given that there are some platforms which have problem with
>> mmio and sil3112/4 can do everything via io accesses, it would be nice
>> to generalize this so that there's CONFIG_SATA_SIL_NO_MMIO which is
>> selected by affected platforms.  Are you interested in doing it?
> 
> Unfortunately I no longer have access to that SIL3512 miniPCI card so
> I wouln't be able to test on IXP425. Perhaps it's not a problem, testing
> on i386 (probably with disabled MMIO BAR) should be enough.
> 
> OTOH IIRC SIL3x12 needs to use the MMIO write to start BM DMA, otherwise
> the AT-style 64 KB limits apply. I think IXP4xx would benefit from only
> ioread8() going through normal IO.
> 
> Do you know what platforms have the MMIO problems? What kind of problems
> are there, inability to use MMIO at all? (IXP4xx can't do 8/16-bit MMIO
> reads).

I don't remember exactly but similar subjects have come up multiple
times on the mailing list and elsewhere.  ISTR a case where MMIO was
completely unavailable but I could be mistaken.  At any rate, the most
common problem seems to be smaller MMIO accesses, so generalizing your
previous patch just a bit would help a lot.
ie. CONFIG_SATA_SIL_ONLY_32BIT_MMIO which is selected by platform.

Thanks.

-- 
tejun
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