linux-kernel - Re: Speed of SDHCI subsystem

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Message-ID: <20090622161147.0769731a@mjolnir.ossman.eu>
Date:	Mon, 22 Jun 2009 16:11:47 +0200
From:	Pierre Ossman <drzeus-list@...eus.cx>
To:	"J.A. Magallón" <jamagallon@....com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Speed of SDHCI subsystem

On Wed, 17 Jun 2009 23:45:50 +0200
"J.A. Magallón" <jamagallon@....com> wrote:

> 
> Thanks, now its clear it is related to hardware limits.
> I suppose this controler is a cheap one...
> Things in the Aspire One are these:
> 

*snip*

> 04:00.0 System peripheral: JMicron Technologies, Inc. SD/MMC Host Controller
> 04:00.2 SD Host controller: JMicron Technologies, Inc. Standard SD Host Controller
> 04:00.3 System peripheral: JMicron Technologies, Inc. MS Host Controller
> 04:00.4 System peripheral: JMicron Technologies, Inc. xD Host Controller

That chip is capable of very high speeds but unfortunately the systems
aren't always properly wired for it so the high-speed mode was disabled
by default in the chips.

You can force it on by applying this patch:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=a4b76193774b463b922cab2f92450efb20d29ef0;hp=d6d8de33415ca7598fe66d933b6556fa8f89afe2

Rgds
-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  rdesktop, core developer          http://www.rdesktop.org
  TigerVNC, core developer          http://www.tigervnc.org

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