Re: [PATCH] drm/rockchip: Return -EBUSY if there's already a pending flip event v2

From: Tomeu Vizoso
Date: Fri Apr 01 2016 - 07:47:39 EST


On 04/01/2016 01:26 PM, Mark yao wrote:
> On 2016å03æ31æ 16:08, Tomeu Vizoso wrote:
>> As per the docs, atomic_commit should return -EBUSY "if an asycnhronous
>> updated is requested and there is an earlier updated pending".
>>
>> v2: Use the status of the workqueue instead of vop->event, and don't add
>> a superfluous wait on the workqueue.
>>
>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
>> ---
>> drivers/gpu/drm/rockchip/rockchip_drm_fb.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>> index 3b8f652698f8..285f8cd5afe1 100644
>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>> @@ -282,6 +282,9 @@ int rockchip_drm_atomic_commit(struct drm_device *dev,
>> struct rockchip_atomic_commit *commit = &private->commit;
>> int ret;
>>
>> + if (async && work_busy(&commit->work))
>> + return -EBUSY;
>> +
>
> Sorry for reply late.
>
> There is a comment on work_busy function describe :
>
> "the test result is unreliable and only useful as advisory hints or
> for debugging."
>
> I don't know if it's suitable to use it here, does some guys know it?

I'm not sure, but if the reason is the caveat explained in
find_worker_executing_work(), then it's probably safe (and would explain
how the function is used in other parts in the kernel).

> And then, the "flush_work(&commit->work);" is no needed if return -EBUSY
> here.
> you can remove it at this patch.

We still need to wait if it's being called in sync mode.

Regards,

Tomeu

>> ret = drm_atomic_helper_prepare_planes(dev, state);
>> if (ret)
>> return ret;
>
>
>
> --
> ïark Yao
>