linux-kernel - Re: QUIRK_FORCE_HISPD (was: Re: Ricoh R5C822 and QUIRK_FORCE

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Message-ID: <20090906153018.6c03d942@mjolnir.ossman.eu>
Date:	Sun, 6 Sep 2009 15:30:18 +0200
From:	Pierre Ossman <pierre@...man.eu>
To:	Tobias Diedrich <ranma@...edrich.de>
Cc:	SDHCI development <sdhci-devel@...ts.ossman.eu>,
	linux-kernel@...r.kernel.org
Subject: Re: QUIRK_FORCE_HISPD (was: Re: Ricoh R5C822 and QUIRK_FORCE_DMA)

On Sat, 1 Aug 2009 07:17:16 +0200
Tobias Diedrich <ranma@...edrich.de> wrote:

> Pierre Ossman wrote:
> > > On a related note, I had a little time to play a bit more with my
> > > R5C822 and found that I can also force-enable HISPD mode, which
> > > boost performance further.
> > > 
> > 
> > This seems odd. What frequency is the controller reporting?
> > 
> > It could be that they originally wanted the controller to be
> > high-speed, but that they had stability problems and turned it off.
> > There is at least one other controller that went through that scenario.
> 
> I assume thats host->max_clk?
> The controller seems to report 33MHz for that value.
> 

Ah, then your controller is most likely not really high-speed. You're
getting a bit more performance as you are forcing things out-of-spec
and you're lucky enough that it still happens to work. :)

Rgds
-- 
     -- Pierre Ossman

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