linux-kernel - Re: MMC: Make the configuration memory resource optional

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Message-ID: <Pine.LNX.4.64.0908051702180.5802@axis700.grange>
Date:	Wed, 5 Aug 2009 21:44:48 +0200 (CEST)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	Ian Molton <ian@...menth.co.uk>
cc:	Magnus Damm <magnus.damm@...il.com>,
	pHilipp Zabel <philipp.zabel@...il.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org, Pierre Ossman <drzeus@...eus.cx>,
	Magnus Damm <damm@...nsource.se>
Subject: Re: MMC: Make the configuration memory resource optional

On Wed, 5 Aug 2009, Ian Molton wrote:

> Hi all,
> 
> Could all non-MFD users of tmio-mmc please ensure that the following is
> actually true on your hardware?
> 
>   mmc->f_max = pdata->hclk;
>   mmc->f_min = mmc->f_max / 512;

That's what I currently have in the driver, yes.

> According to all the data I have, the smallest divider setting of 0x100 is /2
> and only MFD controllers with the CNF area can select no-divider mode.
> 
> this would mean that non-MFD chips should be doing:
> 
>   mmc->f_max = pdata->hclk / 2;
>   mmc->f_min = pdata->hclk / 512;

How do we verify this? Do I need some "very fast" card, so that sd would 
try to drive the clock beyond pdata->hclk / 2, which should then fail? 
Currently I'm using 24MHz (copied from the original driver), and the only 
thing I know about the controller is its "Maximum operating frequency: 25 
MHz."

Thanks
Guennadi
---
Guennadi Liakhovetski
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