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

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Date:	Tue, 24 Mar 2009 21:17:48 +0100
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, 10 Mar 2009 02:21:21 +0100
José María Fernández González <josemariafg@...il.com> wrote:

> 
> I don't know whether this patch can break something in the behavior of other
> SD controllers, but at least it works for my laptop.
> 

Should be fairly safe, it just slows things down.

> diff -Nrpu linux-2.6.28.5/drivers/mmc/core/core.c.orig linux-2.6.28.5/drivers/mmc/core/core.c
> --- linux-2.6.28.5/drivers/mmc/core/core.c.orig	2009-03-10 01:30:19.000000000 +0100
> +++ linux-2.6.28.5/drivers/mmc/core/core.c	2009-03-10 01:29:44.000000000 +0100
> @@ -514,7 +514,7 @@ static void mmc_power_up(struct mmc_host
>  	 * This delay should be sufficient to allow the power supply
>  	 * to reach the minimum voltage.
>  	 */
> -	mmc_delay(2);
> +	mmc_delay(10);
>  

A delay of 10 is just enough to trigger a sleep on most kernels
(HZ=100). Have you determined the lower bound of these two values?

-- 
     -- Pierre Ossman

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

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