Re: [PATCH v2] mmc: sdhci-esdhc-imx: fix abort due to missing runtime PM

[Ulf Hansson]

On 30 March 2015 at 13:37, Stefan Agner <stefan@xxxxxxxx> wrote:
> When entering suspend while the device is in runtime PM, the
> sdhci_(suspend|resume)_host function are called with disabled clocks.
> Since this functions access the SDHC host registers, this leads to an
> external abort on Vybrid SoC:
>
> [   37.772967] Unhandled fault: imprecise external abort (0x1c06) at 0x76f5f000
> [   37.780304] Internal error: : 1c06 [#1] ARM
> [   37.784670] Modules linked in:
> [   37.787908] CPU: 0 PID: 428 Comm: sh Not tainted 3.18.0-rc5-00119-geefd097-dirty #1540
> [   37.796142] task: 8e246c00 ti: 8ca6c000 task.ti: 8ca6c000
> [   37.801785] PC is at esdhc_writel_le+0x40/0xec
> [   37.806431] LR is at sdhci_set_card_detection+0xe0/0xe4
> [   37.811877] pc : [<803f0584>]    lr : [<803eaaa0>]    psr: 400f0013
> [   37.811877] sp : 8ca6dd28  ip : 00000001  fp : 8ca6dd3c
> [   37.823766] r10: 807a233c  r9 : 00000000  r8 : 8e8b7210
> [   37.829194] r7 : 802d8a08  r6 : 8082e928  r5 : 00000000  r4 : 00000002
> [   37.835974] r3 : 8ea34e90  r2 : 00000038  r1 : 00000000  r0 : 8ea32ac0
> ...
>
> Clocks need to be enabled to access the registers. Fix the issue by
> add driver specific implementation of suspend/resume functions which
> take care of clocks using runtime PM API.
>
> Signed-off-by: Stefan Agner <stefan@xxxxxxxx>

Hi Stefan,

Sorry for the delay.

Indeed sdhci seems to have some issues when combining runtime PM and system PM.

> ---
> The first version of this patch was part of a patchset sent back in
> december. While the second patch of the patchset back then is invalid,
> this fix is required to avoid the abort when switching into suspend
> mode on Vybrid SoC.
>
> During review of this patch I realized that my proposed solution to
> fix this in the suspend/resume functions in sdhci-pltfm.c is not a
> good idea since a lot of drivers use this functions without using the
> runtime PM APIs.
>
> Changes since v1:
> - Create new sdhci_esdhc_(suspend|resume) functions in favor of adding a
>   hard requirement for runtime PM on SDHC platform implementations
>
>  drivers/mmc/host/sdhci-esdhc-imx.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index 10ef824..84b3365 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -1119,6 +1119,32 @@ static int sdhci_esdhc_imx_remove(struct platform_device *pdev)
>  }
>
>  #ifdef CONFIG_PM
> +static int sdhci_esdhc_suspend(struct device *dev)
> +{
> +       int ret;
> +       struct sdhci_host *host = dev_get_drvdata(dev);
> +
> +       pm_runtime_get_sync(dev);

This is indeed needed, since else it isn't safe to invoke sdhci_suspend_host().

> +       ret = sdhci_suspend_host(host);
> +       pm_runtime_mark_last_busy(dev);
> +       pm_runtime_put_autosuspend(dev);

The problem is, that this wont do what you think I believe.

The device will be kept runtime PM resumed, since the PM core has
increased a runtime PM reference count for your device, in the
->prepare() phase (pm_runtime_get_noresume()).

Potentially pm_runtime_force_suspend() could help you accomplish what you want.

> +
> +       return ret;
> +}
> +
> +static int sdhci_esdhc_resume(struct device *dev)
> +{
> +       int ret;
> +       struct sdhci_host *host = dev_get_drvdata(dev);
> +
> +       pm_runtime_get_sync(dev);
> +       ret = sdhci_resume_host(host);
> +       pm_runtime_mark_last_busy(dev);
> +       pm_runtime_put_autosuspend(dev);
> +

Similar comments as above.

> +       return ret;
> +}
> +
>  static int sdhci_esdhc_runtime_suspend(struct device *dev)
>  {
>         struct sdhci_host *host = dev_get_drvdata(dev);
> @@ -1154,7 +1180,7 @@ static int sdhci_esdhc_runtime_resume(struct device *dev)
>  #endif
>
>  static const struct dev_pm_ops sdhci_esdhc_pmops = {
> -       SET_SYSTEM_SLEEP_PM_OPS(sdhci_pltfm_suspend, sdhci_pltfm_resume)
> +       SET_SYSTEM_SLEEP_PM_OPS(sdhci_esdhc_suspend, sdhci_esdhc_resume)
>         SET_RUNTIME_PM_OPS(sdhci_esdhc_runtime_suspend,
>                                 sdhci_esdhc_runtime_resume, NULL)
>  };
> --
> 2.3.3
>

Kind regards
Uffe
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