Re: [PATCH] sdio: fix suspend/resume regression

Chris Ball
2010-10-14T02:24:52Z

Hi Ohad,

On Wed, Oct 13, 2010 at 09:31:56AM +0200, Ohad Ben-Cohen wrote:
> Fix SDIO suspend/resume regression introduced by
> 4c2ef25fe0b847d2ae818f74758ddb0be1c27d8e "mmc: fix all hangs related to
> mmc/sd card insert/removal during suspend/resume":
>
> [ 5647.295953] PM: Syncing filesystems ... done.
> [ 5647.318792] Freezing user space processes ... (elapsed 0.01 seconds) done.
> [ 5647.337048] Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done.
> [ 5647.356915] Suspending console(s) (use no_console_suspend to debug)
> [ 5647.366651] pm_op(): platform_pm_suspend+0x0/0x5c returns -38
> [ 5647.366671] PM: Device pxa2xx-mci.0 failed to suspend: error -38
> [ 5647.367082] PM: Some devices failed to suspend
>
> 4c2ef25fe0b847d2ae818f74758ddb0be1c27d8e moved the card removal/insertion
> mechanism out of MMC's suspend/resume path and into pm notifiers
> (mmc_pm_notify), and that broke SDIO's expectation that mmc_suspend_host()
> will remove the card, and squash the error, in case -ENOSYS is returned
> from the bus suspend handler (mmc_sdio_suspend() in this case).
>
> mmc_sdio_suspend() is using this whenever at least one of the card's SDIO
> function drivers does not have suspend/resume handlers - in that case
> it is agreed to force removal of the entire card.
>
> This patch fixes this regression by trivially bringing back that part of
> mmc_suspend_host(), which was removed by 4c2ef25fe0b847d2ae818f74758ddb0be1c27d8e.
>
> Reported-and-tested-by: Sven Neumann <s.neumann@raumfeld.com>
> Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
> Cc: Maxim Levitsky <maximlevitsky@gmail.com>
> Cc: <stable@kernel.org>
> --
>
> It may still be desired to further clean this area up by using the card
> removal mechanism in mmc_pm_notify() for SDIO as well.
>
> To use mmc_pm_notify's card-removal code also for SDIO, we need it
> to check if all the SDIO functions have suspend handlers. That
> would probably make us add a new bus_ops handler (something like
> host->bus_ops->remove_card_on_suspend ?).
>
> It's starting to get a bit complicated though, and I'm not sure it
> would make the code a lot more readable.
>
> In addition, this would still not work for drivers like libertas sdio,
> which do have a suspend handler, but sometimes let it return -ENOSYS,
> expecting mmc_suspend_host() to remove the card and squash the error.
> For those cases, we still need the old card-removal logic in mmc_suspend_host().
>
> This brings up a question whether libertas_sdio really needs this
> functionality; When MMC_PM_KEEP_POWER is not needed, can't it just return 0
> (and as a result the card will be powered down, but not removed) ?
>
> Until we have an agreement on this, I suggest we at least fix the
> regression with this patch.
>
> Thanks Sven Neumann for reporting and testing the issue and this patch.
>
> drivers/mmc/core/core.c | 13 +++++++++++++
> 1 files changed, 13 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index c94565d..515ff39 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1682,6 +1682,19 @@ int mmc_suspend_host(struct mmc_host *host)
> if (host->bus_ops && !host->bus_dead) {
> if (host->bus_ops->suspend)
> err = host->bus_ops->suspend(host);
> + if (err == -ENOSYS || !host->bus_ops->resume) {
> + /*
> + * We simply "remove" the card in this case.
> + * It will be redetected on resume.
> + */
> + if (host->bus_ops->remove)
> + host->bus_ops->remove(host);
> + mmc_claim_host(host);
> + mmc_detach_bus(host);
> + mmc_release_host(host);
> + host->pm_flags = 0;
> + err = 0;
> + }
> }
> mmc_bus_put(host);
>
> --

Thanks very much, I've applied this to mmc-next with Nicolas' ACK.

--
Chris Ball <cjb@laptop.org> <http://printf.net/>
One Laptop Per Child