Investigating SD card failures

Investigating SD card failures

[Manuel Lauss]

Hi Pierre,

I have a 1GB SanDisk SD card here which linux does not recognize.
Looking at the MMC debug output, I see the MMC core repeatedly
issues CMD55/CMD41 commands (which all succeed!) then stops
after 100 times.  In sd_ops.c the code checks for a bit to get set.
My question is, what exactly is this bit supposed to indicate?

Thanks,
	Manuel Lauss

Re: Investigating SD card failures

[Pierre Ossman]

On Fri, 27 Jul 2007 07:50:26 +0200
Manuel Lauss <mano@roarinelk.homelinux.net> wrote:

> Hi Pierre,
> 
> I have a 1GB SanDisk SD card here which linux does not recognize.
> Looking at the MMC debug output, I see the MMC core repeatedly
> issues CMD55/CMD41 commands (which all succeed!) then stops
> after 100 times.  In sd_ops.c the code checks for a bit to get set.
> My question is, what exactly is this bit supposed to indicate?
> 

That the card has initialized. Try extending the time that loop runs and see if the card powers up.

-- 
     -- Pierre Ossman

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

Re: Investigating SD card failures

[Manuel Lauss]

Hi Pierre,

Thank your for your answer!

Pierre Ossman wrote:
> On Fri, 27 Jul 2007 07:50:26 +0200
> Manuel Lauss <mano@roarinelk.homelinux.net> wrote:
> 
>> Hi Pierre,
>>
>> I have a 1GB SanDisk SD card here which linux does not recognize.
>> Looking at the MMC debug output, I see the MMC core repeatedly
>> issues CMD55/CMD41 commands (which all succeed!) then stops
>> after 100 times.  In sd_ops.c the code checks for a bit to get set.
>> My question is, what exactly is this bit supposed to indicate?
>>
> 
> That the card has initialized. Try extending the time that loop runs and see if the card powers up.

Did that, waited almost 10 seconds, didn't help.  I found a printed
version of the SD spec; it turned out to be a power supply problem.
Apparently the power supply is not strong enough and/or the card
very sensitive to power fluctuations; put in another piece of hardware
with redesigned power supply the card works fine.

Sorry for the noise!

Thanks,
	Manuel Lauss