Occasional crashes in suspend-resume with MMC transactions

[Hebbar, Gururaja]

On Thu, Mar 22, 2012 at 19:57:16, S, Venkatraman wrote:
> On Thu, Mar 22, 2012 at 6:50 PM, Bedia, Vaibhav <vaibhav.bedia at ti.com> wrote:
> > On Thu, Mar 22, 2012 at 09:53:23, Bedia, Vaibhav wrote:
> >> Hi,
> >>
> >> I am trying to do suspend-resume test with a file copy on MMC/SD going on
> >> in the background. The test involves simply copying a 450MB file on an ext3
> >> partition to the same partition under a different name.
> >>
> >> This is on an AM335x board which uses the omap_hsmmc driver.
> >> The kernel is v3.2 and I have also applied the following patch
> >>
> >
> > [...]
> >
> > I found that whenever this issue crops up, mmc_host_suspend() is not able to claim the host
> > And returns -EBUSY. omap_hsmmc driver does not pass on this error code to the PM core and
> > hence the suspend process continues. When the driver is made to return -EBUSY, the suspend
> > process gets aborted and the user can try suspending again. I am not sure whether this sort
> > of suspend failure is acceptable or the driver is doing something wrong. The following
> > workaround is what I came up with. Do this look a reasonable thing to do?
> >
> > ---
> >
> > From a4040dd1869b351a5fa29dacd08facf6e24df609 Mon Sep 17 00:00:00 2001
> > From: Vaibhav Bedia <vaibhav.bedia at ti.com>
> > Date: Thu, 22 Mar 2012 17:14:49 +0530
> > Subject: [PATCH 1/1] mmc: omap_hsmmc: Pass on the suspend failure to the PM core
> >
> > In some cases mmc_host_suspend() is not able to claim the
> > host and proceed with the suspend process. The core returns
> > -EBUSY to the host controller driver. Unfortunately, the
> > host controller driver does not pass on this information
> > to the PM core and hence the system suspend process continues.
> >
> > In these cases the MMC core gets to an unexpected state
> > during resume and multiple issues related to MMC crop up.
> > 1. Host controller driver starts accessing the device registers
> > before the clocks are enabled which leads to a prefetch abort.
> > 2. A file copy thread which was launched before suspend gets
> > stuck due to the host not being reclaimed during resume.
> >
> > To avoid such problems pass on the -EBUSY status to the PM core
> > from the host controller driver. With this change, MMC core
> > suspend might still fail but it does not end up making the
> > system unusable. Suspend gets aborted and the user can try
> > suspending the system again.
> >
> > Signed-off-by: Vaibhav Bedia <vaibhav.bedia at ti.com>
> > ---
> >  drivers/mmc/host/omap_hsmmc.c |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> > index 3d8dbbb..1f938d9 100644
> > --- a/drivers/mmc/host/omap_hsmmc.c
> > +++ b/drivers/mmc/host/omap_hsmmc.c
> > @@ -2238,6 +2238,7 @@ static int omap_hsmmc_suspend(struct device *dev)
> >                                        dev_dbg(mmc_dev(host->mmc),
> >                                                "Unmask interrupt failed\n");
> >                        }
> > +                       ret = -EBUSY;
> >                        goto err;
> >                }
> >
> > --
> > 1.7.0.4
> 
> I see (in 3.3) that the host controller driver does a "return ret" and
> that means the errors is propagated.
> Where is the return code lost /overridden ?

As seen from http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=drivers/mmc/host/omap_hsmmc.c;h=fd0c661bbad38a7152a37955146ff6068d4d7137;hb=refs/tags/v3.3

omap_hsmmc.c 

@ 2045

pdata->resume = omap_hsmmc_resume_cdirq;


@227

static int omap_hsmmc_resume_cdirq(struct device *dev, int slot)
{
        struct omap_mmc_platform_data *mmc = dev->platform_data;

        enable_irq(mmc->slots[0].card_detect_irq);
        return 0;							-----> always return 0
}

@2167

                        if (host->pdata->resume) {
                                ret = host->pdata->resume(&pdev->dev,		--> ret becomes zero irrespective of its previous value.
                                                          host->slot_id);
                                if (ret)
                                        dev_dbg(mmc_dev(host->mmc),
                                                "Unmask interrupt failed\n");
                        }


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Regards, 
Gururaja