Hi Krzysztof,
On Fri, Jan 30, 2015 at 10:46 AM, Krzysztof Kozlowski
<k.kozlowski@xxxxxxxxxxx> wrote:
> 2015-01-05 11:46 GMT+01:00 Geert Uytterhoeven <geert+renesas@xxxxxxxxx>:
>> 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@xxxxxxxxx>
>> ---
>> 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.
I don't think new requests can come in while .shutdown() is called, so
the device cannot be resumed here.
>> + 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
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
--
To unsubscribe from this list: send the line "unsubscribe dmaengine" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
