Tracking down suspend/resume ext3/mmc issues on imx233

[Mike Thompson]

I figured the source of my problem.  Normally, the Linux kernel will
treat mmc cards as removed during suspend.  This is in case the card
is swapped by the user during the suspend.  However, on the OLinuXino
the mmc device is the root file system  If the Linux kernel treats the
mmc card as removed the frozen tasks with open file handles to the
root filesystem device (such as the journal tasks) will fail when they
are thawed during resume.  This is the problem I was seeing.

Fortunately, there is already a specific kernel config setting
CONFIG_MMC_UNSAFE_RESUME that needs to be set for systems such as the
OLinuXino that uses the mmc device for the root filesystem.  I
overlooked this config setting and spent half a day trying to figure
out the source of the file system errors on resume.  Next time I'll do
a better job of looking through related config settings before trying
to debug an issue that is probably already dealt with.

Mike

On Thu, Sep 6, 2012 at 11:05 PM, Shawn Guo <shawn.guo at linaro.org> wrote:
> Copy a few more lists to get wider audience ...
>
> Regards,
> Shawn
>
> On Thu, Sep 06, 2012 at 10:03:35PM -0700, Mike Thompson wrote:
>> I'm working on adding power management support for the imx233 on
>> 3.6-rc2.  In general I'm working on porting the pm.c file from the
>> Freescale 2.6.35 kernel for both "standby" and "mem" suspend/resume.
>> I'm making pretty good progress on porting the code, but I'm running
>> into an issue outside the immediate code I'm working on.
>>
>> ...
>>
>> The first reported error is in the ext3 filesystem buffer code where
>> the file system buffers aren't being filled by the underlying block
>> device.  At least that's how I'm interpreting the portion of the ext3
>> file system code that is failing.  However, the mmc device is
>> correctly reporting finding p1 and p2 partitions on the device which
>> it would indicate the partition data is being read from the SD card.
>>
>> I'm hoping others might have suggestions on how I should go about
>> tracking down why the ext3 file system can no longer read from the mmc
>> device upon resume.  For instance, useful places to put some tracing
>> code to understand what might be failing, or how to determine what
>> differences there might be before suspend and after resume that might
>> point to the failure.
>>
>> Thanks,
>>
>> Mike Thompson
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel at lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel