3.18-rc2 boot failure on Radxa Rock in dw_mmc

[Max Schwarz]

Hi Doug,

On Saturday 01 November 2014 at 13:50:16, Doug Anderson wrote:
> Max,
> 
> On Sat, Nov 1, 2014 at 7:03 AM, Max Schwarz <max.schwarz at online.de> wrote:
> > Hi all,
> > 
> > I'm getting an Oops during boot of 3.18-rc2 on my Radxa Rock. It only
> > happens when a microSD card is inserted.
> > 
> > Full boot log: https://gist.github.com/xqms/ff6fc22407e705c9986d
> > My .config: https://gist.github.com/xqms/9f80f9f9601f85d399cf
> > 
> > The issue seems to be in the dw-mmc driver. It seems that an IRQ is
> > triggered before the host->slot[i] pointer is initialized, causing the
> > fault in line 2066 of drivers/mmc/host/dw_mmc.c:
> > 
> > static void dw_mci_work_routine_card(struct work_struct *work)
> > {
> > 
> >         struct dw_mci *host = container_of(work, struct dw_mci,
> >         card_work);
> >         int i;
> >         
> >         for (i = 0; i < host->num_slots; i++) {
> >         
> >                 struct dw_mci_slot *slot = host->slot[i];
> >                 struct mmc_host *mmc = slot->mmc; <-- FAULT
> >                 struct mmc_request *mrq;
> 
> Yup.  Sounds familiar.  See
> <https://patchwork.kernel.org/patch/4829341/>.  I later decided that I
> hadn't thought through everything enough so I ended up dropping the
> patch.  There is definitely a race here and it's existed for a long
> time, I just wasn't sure my patch was the right fix.  Amazingly the
> problem disappeared for me (not that I liked that as a fix).
> 
> > A bisect ends at:
> > 
> > commit 51da2240906cb94e8f6ba55e403b6206df6fb2dd
> > Author: Yuvaraj CD <yuvaraj.cd at gmail.com>
> > Date:   Fri Aug 22 19:17:50 2014 +0530
> > 
> >     mmc: dw_mmc: use mmc_regulator_get_supply to handle regulators
> >     
> >     This patch makes use of mmc_regulator_get_supply() to handle
> >     the vmmc and vqmmc regulators.Also it moves the code handling
> >     the these regulators to dw_mci_set_ios().It turned on the vmmc
> >     and vqmmc during MMC_POWER_UP and MMC_POWER_ON,and turned off
> >     during MMC_POWER_OFF.
> >     
> >     Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd at samsung.com>
> >     Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
> > 
> > That seems a bit unrelated to me, but maybe it causes a different
> > initialization order?
> > 
> > I'm playing around with the initialization order myself, but I haven't
> > managed to find a working configuration yet. Can somebody with MMC
> > knowledge find the problem or point me into the right direction?
> 
> For me the problem randomly came and then randomly disappeared.
> Others working on the same kernel would see it, then they wouldn't.

Okay thanks, good to know it's not just me. It appeared with 3.18 for me, so I 
thought it would be good to fix it for the next -rc. But if the bug is older 
and something is in the works to fix it, I'm satisfied ;-)

> ...if you want a fix, try grabbing (5998ad0 mmc: dw_mmc: Remove old
> card detect infrastructure) from linuxnext.  That kills the work
> routine.  I also threw an "if (!slot)" in there just because I was
> worried about the problem coming back and I figured that it was better
> not to crash.

Thanks, will try that.

Cheers,
  Max