[PATCH] drm: simple_kms_helper: Handle the vblank events

[Marek Vasut]

On 09/29/2016 11:28 AM, Daniel Vetter wrote:
> On Tue, Sep 27, 2016 at 02:20:49PM +0200, Marek Vasut wrote:
>> On 09/27/2016 02:16 PM, Noralf Trønnes wrote:
>>>
>>> Den 27.09.2016 12:29, skrev Marek Vasut:
>>>> On 09/27/2016 09:49 AM, Daniel Vetter wrote:
>>>>> On Mon, Sep 26, 2016 at 2:59 PM, Marek Vasut <marex at denx.de> wrote:
>>>>>> On 09/26/2016 11:41 AM, Marek Vasut wrote:
>>>>>>> On 09/25/2016 11:00 PM, Daniel Vetter wrote:
>>>>>>>> On Sun, Sep 25, 2016 at 09:41:58PM +0200, Marek Vasut wrote:
>>>>>>>>> Handle the vblank events in the simple_kms_helper driver, otherwise
>>>>>>>>> the drm_atomic_helper flip_done event never happens.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>>>>>>>> Cc: Noralf Trønnes <noralf at tronnes.org>
>>>>>>>>> Cc: Daniel Vetter <daniel at ffwll.ch>
>>>>>>>>> Cc: David Airlie <airlied at linux.ie>
>>>>>>>>> ---
>>>>>>>>>   drivers/gpu/drm/drm_simple_kms_helper.c | 18 ++++++++++++++++++
>>>>>>>>>   1 file changed, 18 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>>>> index 7b6d26e..3345b40 100644
>>>>>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>>>> @@ -34,6 +34,23 @@ static const struct drm_encoder_funcs
>>>>>>>>> drm_simple_kms_encoder_funcs = {
>>>>>>>>>      .destroy = drm_encoder_cleanup,
>>>>>>>>>   };
>>>>>>>>>
>>>>>>>>> +static void drm_simple_kms_crtc_begin(struct drm_crtc *crtc,
>>>>>>>>> +                                 struct drm_crtc_state *state)
>>>>>>>>> +{
>>>>>>>>> +   struct drm_pending_vblank_event *event = crtc->state->event;
>>>>>>>>> +
>>>>>>>>> +   if (event) {
>>>>>>>>> +           crtc->state->event = NULL;
>>>>>>>>> +
>>>>>>>>> +           spin_lock_irq(&crtc->dev->event_lock);
>>>>>>>>> +           if (drm_crtc_vblank_get(crtc) == 0)
>>>>>>>>> +                   drm_crtc_arm_vblank_event(crtc, event);
>>>>>>>>> +           else
>>>>>>>>> +                   drm_crtc_send_vblank_event(crtc, event);
>>>>>>>>> +           spin_unlock_irq(&crtc->dev->event_lock);
>>>>>>>>> +   }
>>>>>>>>> +}
>>>>>>>> This should be done by drivers, in the ->update hook. At least if
>>>>>>>> we want
>>>>>>>> to pretend that it's semi-accurate and not racy (which the above is).
>>>>>>>> -Daniel
>>>>>>> Got it and wrapped into mxsfb, thanks.
>>>>>> Hrm, while this works most of the time, I managed to get a page_flip
>>>>>> timeout when terminating the kmscube OpenGL demo (see below). I'm not
>>>>>> getting this splat with this patch applied. Any idea what this could
>>>>>> mean ?
>>>>> Are you on latest drm-next?
>>>> No, I'm on next/master from 20160927 . Is this the right tree?
>>>> https://cgit.freedesktop.org/~airlied/linux/log/?h=drm-next
>>>>
>>>>> There was a bug fixed for 4.9 which
>>>>> resulted in the primary plane not always being added to the state,
>>>>> which means that the ->update hook would not get called when the plane
>>>>> is getting disabled.
>>>> Ah, which patch ?
>>>
>>> I believe this is the one:
>>>
>>> drm/simple-helpers: Always add planes to the state update
>>> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/drivers/gpu/drm/drm_simple_kms_helper.c?id=6dcf0de7ef10244b17442f47956a1d9fabe2abe1
>>
>> Thanks. I have that one in my tree already.
> 
> Can you pls check that for the case where you hit the WARN the simple
> pipe's ->update function is called, and that you're indeed handling the
> event in all cases?

The update is called, but I check whether I have plane->state->crtc
non-NULL in the update function of mxsfb as I need to fish out the
crtc->state->event from it. This plane->state->crtc is NULL in case when
I get the backtrace. I can access the crtc via &pipe->crtc though, which
is what I should probably do, right ?

> -Daniel
> 


-- 
Best regards,
Marek Vasut