Re: [PATCH v2] dmaengine: shdma: Runtime-resume device in .shutdown()

[Krzysztof Kozlowski <k.kozlowski@samsung.com>]

2015-01-05 11:46 GMT+01:00 Geert Uytterhoeven <geert+renesas@glider.be>:
> During system reboot, the sh-dma-engine device may be runtime-suspended,
> causing a crash:
>
>     Unhandled fault: imprecise external abort (0x1406) at 0x0002c02c
>     Internal error: : 1406 [#1] SMP ARM
>     ...
>     PC is at sh_dmae_ctl_stop+0x28/0x64
>     LR is at sh_dmae_ctl_stop+0x24/0x64
>
> If the sh-dma-engine is runtime-suspended, its module clock is turned
> off, and its registers cannot be accessed.
>
> To fix this, change the driver's .shutdown() callback:
>   - If the device is runtime suspended, do nothing,
>   - Else, explicitly runtime-resume the device, to avoid the device from
>     being suspended while sh_dmae_ctl_stop() is being executed.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> v2:
>   - Do nothing if we're runtime suspended.
> ---
>  drivers/dma/sh/shdmac.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/dma/sh/shdmac.c b/drivers/dma/sh/shdmac.c
> index aec8a84784a469d7..2de30e8e7d9290b9 100644
> --- a/drivers/dma/sh/shdmac.c
> +++ b/drivers/dma/sh/shdmac.c
> @@ -585,7 +585,13 @@ static void sh_dmae_chan_remove(struct sh_dmae_device *shdev)
>  static void sh_dmae_shutdown(struct platform_device *pdev)
>  {
>         struct sh_dmae_device *shdev = platform_get_drvdata(pdev);
> +
> +       if (pm_runtime_suspended(&pdev->dev))

This still looks a little racy. What if runtime resume happens exactly
here? I think safer would be disabling runtime PM before checking for
suspend state.

Best regards,
Krzysztof

> +               return;
> +
> +       pm_runtime_get_sync(&pdev->dev);
>         sh_dmae_ctl_stop(shdev);
> +       pm_runtime_put(&pdev->dev);
>  }
>
>  static int sh_dmae_runtime_suspend(struct device *dev)
> --
> 1.9.1
>
> --
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