linux-kernel - Re: [PATCH 1/1] mmc: Some microSD cards are not recognized by PCIxx12 SDA controller

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Date:	Fri, 10 Apr 2009 23:35:46 +0200
From:	Pierre Ossman <drzeus-list@...eus.cx>
To:	José María Fernández González 
	<josemariafg@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] mmc: Some microSD cards are not recognized by
 PCIxx12 SDA controller

On Tue, 07 Apr 2009 01:30:28 +0200
José María Fernández González <josemariafg@...il.com> wrote:

> It is curious. I have concentrated my tests on 2.6.29 with HZ=100 and no preemption, and I have done next tests with my microSD card and laptop:
> 
> *	mmc_delay(2) -> FAIL
> *	mdelay(2) -> FAIL
> *	mmc_delay(10) -> Works!
> *	mdelay(10) -> Works!
> 

Looks good. Although it would have been nice to also know exactly when
it starts working.

> And by mistake I found that:
> 
> *	msleep(2) -> Works!
> 

This is the scheduling effect I was talking about. Basically you can
never get msleep() to delay shorter than 1/HZ seconds.

I'll queue up your patch.

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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