[PATCH] drm: simple_kms_helper: Handle the vblank events

Tue Sep 27 07:49:10 UTC 2016

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? 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.

At least that's my guess, the WARN_ON just tells you that no one sent
out the event yet, but by that point it should have happened.
-Daniel

>
>  ------------[ cut here ]------------
>  WARNING: CPU: 0 PID: 77 at drivers/gpu/drm/drm_atomic_helper.c:1579
> drm_atomic_helper_commit_hw_done+0xa8/0xb8
>  Modules linked in:
>  CPU: 0 PID: 77 Comm: kworker/0:2 Tainted: G        W
> 4.8.0-rc7-next-20160923-00033-ge3f15d6 #56
>  Hardware name: Freescale i.MX6 SoloX (Device Tree)
>  Workqueue: events drm_mode_rmfb_work_fn
>  Backtrace:
>  [<c010c180>] (dump_backtrace) from [<c010c378>] (show_stack+0x18/0x1c)
>   r7:00000000 r6:600e0013 r5:00000000 r4:c0e2342c
>  [<c010c360>] (show_stack) from [<c03f4ad8>] (dump_stack+0xb4/0xe8)
>  [<c03f4a24>] (dump_stack) from [<c0124a90>] (__warn+0xd8/0x104)
>   r9:c04bdb60 r8:0000062b r7:00000009 r6:c0c38298 r5:00000000 r4:00000000
>  [<c01249b8>] (__warn) from [<c0124b70>] (warn_slowpath_null+0x28/0x30)
>   r9:db43639c r8:0000062b r7:c0c38298 r6:da962e40 r5:00000000 r4:00000000
>  [<c0124b48>] (warn_slowpath_null) from [<c04bdb60>]
> (drm_atomic_helper_commit_hw_done+0xa8/0xb8)
>  [<c04bdab8>] (drm_atomic_helper_commit_hw_done) from [<c04c0568>]
> (drm_atomic_helper_commit_tail+0x44/0x60)
>   r10:c0c3bd84 r9:c0c371cc r8:db770000 r7:db770000 r6:00000000 r5:db770000
>   r4:daffa780 r3:daffa3c0
>  [<c04c0524>] (drm_atomic_helper_commit_tail) from [<c04c05e8>]
> (commit_tail+0x64/0x68)
>   r5:00000000 r4:daffa780
>  [<c04c0584>] (commit_tail) from [<c04c06b0>]
> (drm_atomic_helper_commit+0xac/0xec)
>   r5:00000000 r4:daffa780
>  [<c04c0604>] (drm_atomic_helper_commit) from [<c04e11b4>]
> (drm_atomic_commit+0x58/0x78)
>   r7:db436028 r6:db770000 r5:daffa780 r4:00000000
>  [<c04e115c>] (drm_atomic_commit) from [<c04c0be4>]
> (drm_atomic_helper_set_config+0x80/0xa4)
>   r6:dad37e14 r5:00000000 r4:daffa780
>  [<c04c0b64>] (drm_atomic_helper_set_config) from [<c04d35fc>]
> (drm_mode_set_config_internal+0x6c/0xfc)
>   r7:db77048c r6:db770480 r5:db436028 r4:00000000
>  [<c04d3590>] (drm_mode_set_config_internal) from [<c04d36c4>]
> (drm_crtc_force_disable+0x38/0x40)
>   r7:db77048c r6:db770480 r5:da962c00 r4:db436028
>  [<c04d368c>] (drm_crtc_force_disable) from [<c04e2b60>]
> (drm_framebuffer_remove+0xd8/0x124)
>  [<c04e2a88>] (drm_framebuffer_remove) from [<c04e2bec>]
> (drm_mode_rmfb_work_fn+0x40/0x50)
>   r10:00000001 r9:00000000 r8:dbbb2a00 r7:dad37ea8 r6:dbbaf800 r5:db60be68
>   r4:db60be48
>  [<c04e2bac>] (drm_mode_rmfb_work_fn) from [<c013fa10>]
> (process_one_work+0x24c/0x4e8)
>   r5:dad12f00 r4:db60be48
>  [<c013f7c4>] (process_one_work) from [<c01408dc>]
> (worker_thread+0x40/0x574)
>   r10:dad12f00 r9:dad36000 r8:c0e02100 r7:dbbaf834 r6:00000008 r5:dad12f18
>   r4:dbbaf800
>  [<c014089c>] (worker_thread) from [<c0146908>] (kthread+0xd8/0xf8)
>   r10:00000000 r9:00000000 r8:00000000 r7:c014089c r6:dad12f00 r5:dad28500
>   r4:00000000
>  [<c0146830>] (kthread) from [<c0107cb0>] (ret_from_fork+0x14/0x24)
>   r7:00000000 r6:00000000 r5:c0146830 r4:dad28500
>  ---[ end trace 2b6e3065f0299ba5 ]---
>
>> But then, I see a few drivers (arm hdlcd, fsl-dcu,...) doing the same
>> thing at random callbacks of CRTC . Shouldn't this event handling be
>> consolidated into some generic function and those drivers fixed to
>> call it from atomic update ?
>>
>
>
> --
> Best regards,
> Marek Vasut

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch