Occasional crashes in suspend-resume with MMC transactions

[S, Venkatraman]

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 ?