On 22/06/2022 20:33, Rob Clark wrote:
On Wed, Jun 22, 2022 at 10:24 AM Abhinav Kumar
<quic_abhinavk@xxxxxxxxxxx> wrote:
On 6/21/2022 7:38 PM, Stephen Boyd wrote:
The 'vsync_cnt' is used to count the number of frames for a crtc.
Unfortunately, we increment the count after waking up userspace via
dpu_crtc_vblank_callback() calling drm_crtc_handle_vblank().
drm_crtc_handle_vblank() wakes up userspace processes that have called
drm_wait_vblank_ioctl(), and if that ioctl is expecting the count to
increase it won't.
Increment the count before calling into the drm APIs so that we don't
have to worry about ordering the increment with anything else in drm.
This fixes a software video decode test that fails to see frame counts
increase on Trogdor boards.
Cc: Mark Yacoub <markyacoub@xxxxxxxxxxxx>
Cc: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
Fixes: 885455d6bf82 ("drm/msm: Change dpu_crtc_get_vblank_counter to use vsync count.")
Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
This is right, we should increment before drm_crtc_handle_vblank() as
that will query the vblank counter. This also matches what we do
downstream, hence
Reviewed-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
One small nit though, shouldnt the fixes tag be
25fdd5933e4c ("drm/msm: Add SDM845 DPU support")
*Kinda*.. but the sw vblank counter wasn't used for reporting frame nr
to userspace until 885455d6bf82. You could possibly list both,
perhaps, but 885455d6bf82 is the important one for folks backporting
to stable kernels to be aware of
I'd agree, the original Fixes tag seems good to me.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
--
With best wishes
Dmitry
