linux-kernel - Re: [PATCH] [9/50] mmc: Added quirks for Ricoh 1180:e823 lower base clock

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Date:	Fri, 29 Jul 2011 11:10:45 +0900
From:	matsumur@....ricoh.co.jp
To:	cjb@...top.org
Cc:	ak@...ux.intel.com, Andi Kleen <andi@...stfloor.org>,
	daniel.manrique@...onical.com, jbarnes@...tuousgeek.org,
	linux-kernel@...r.kernel.org, manoj.iyer@...onical.com,
	stable@...nel.org, tim.bird@...sony.com
Subject: Re: [PATCH] [9/50] mmc: Added quirks for Ricoh 1180:e823 lower base clock

Hi Chris,

> Do you know of a better solution than always lowering the clock speed to
> 50MHz for this controller?

Yes, it is a better solution.
As you know, SD ver.1.1 and 2.0(SDHC) cards can be applied 50MHz SD-CLK..
SD 3.0 (UHS-I) cards also can be applied 50Mhz. However UHS-I cards are
available 200 or 100Mhz SD-CLK.
I would like to know if the current SD Host driver has the function of
setting SD-CLK to 200Mhz for SD ver3.0 compliant Host Controller.


Thanks,


Koji Matsumuro
Ricoh Company,Ltd.


Chris Ball <cjb@...top.org> wrote on 2011/07/29 09:47:53:

> Hi,

> On Thu, Jul 28 2011, Andi Kleen wrote:
> > On Fri, Jul 29, 2011 at 09:27:56AM +0900, matsumur@....ricoh.co.jp
wrote:
> >> Dear Sir,
> >>
> >> Ricoh 1180:e823 device is named R5U220/R5U232 (2 devices have the same
> >> device ID ).
> >> So, I think it should be declared to as PCI_DEVICE_ID_RICOH_R5U220.
> >
> > Is that just the wrong name or will it actually cause misfunction?

> I don't think it could possibly cause misfunction; it's just a macro
name.

> > BTW, does anyone know whether the current SDHCI-driver sets 200Mhz to
> > SD-CLK for UHS-I cards ?

> The Linux 3.1 SD driver will set the SD-CLK to 50MHz for every card on an
> e823 device, and older kernels will do so too once the commit has been
> applied to the stable trees.  See this commit:

> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;
> a=commitdiff;h=15bed0f2fa8e1d7db201692532c210a7823d2d21

> Do you know of a better solution than always lowering the clock speed to
> 50MHz for this controller?

> Thanks,

> - Chris.
> --
> Chris Ball   <cjb@...top.org>   <http://printf.net/>
> One Laptop Per Child

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