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

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Message-ID: <4B28170F.9010808@pobox.com>
Date:	Tue, 15 Dec 2009 18:09:03 -0500
From:	Jeff Garzik <jgarzik@...ox.com>
To:	Krzysztof Halasa <khc@...waw.pl>
CC:	Tejun Heo <tj@...nel.org>, linux-ide@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: SATA_SIL: Add a work-around for IXP4xx CPU.

On 12/15/2009 06:03 PM, 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).

The inability to do 8/16-bit MMIO reads are a repeated sticking point 
with embedded scenarios.  That's it.

I keep meaning to give the docs a hard look, and see if we can combine 
multiple taskfile register reads/writes into a single 32-bit one.  That 
would solve all these problems, without having to resort to the use of 
standard BARs.

	Jeff



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