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

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Message-ID: <20090613125322.750a1180@mjolnir.ossman.eu>
Date:	Sat, 13 Jun 2009 12:53:22 +0200
From:	Pierre Ossman <pierre@...man.eu>
To:	Tobias Diedrich <ranma+kernel@...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 Wed, 10 Jun 2009 00:41:45 +0200
Tobias Diedrich <ranma+kernel@...edrich.de> wrote:

> Pierre Ossman wrote:
> > Might be a system problem so it's Lenovo that disabled it. You're the
> > first report I've seen on this since the DMA logic was reworked so that
> > DMA didn't have to be forced for most cases.
> 
> FWIW, so far I haven't had any errors due to dma being enabled.
> 
> I tried changing the CAPS using setpci, but they seem to be
> read-only (unless theres are write-protect bit somewhere in the
> config space).

They tend to be write-protected, yes. Usually there are some other
registers you need to fiddle with first.

> 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 tried improving the write speed by adding support for
> APP_CMD_SET_WR_BLOCK_COUNT to the block driver, but did not see any
> improvement.
> It's still in the patch, in case you are interested.

I've tried this before, and I got the same results you did.

Rgds
-- 
     -- Pierre Ossman

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