Frank Chen

Dual OpenGL application v-sync issue on i.MX6Q

Discussion created by Frank Chen on May 24, 2019
Latest reply on May 29, 2019 by Frank Chen

Hi, we got an issue about i.MX6 dual OpenGL applications (render to two framebuffers).


Customer board based on i.MX6Q sabresd.
Linux BSP
GPU driver and sdk: L3.0.35_4.0.0


fb0: PAL TVout, refresh rate 50Hz
fb2: HDMI, refresh rate 60Hz


OpenGL app1: render to fb0
OpenGL app2: render to fb2


The OpenGL applications are developed based on the samples in gpu_sdk_v1.00.tar.gz.


When the OpenGL applications render frames, the frames are synced with framebuffer v-sync. So the applications can run at the framerate same to the framebuffer refresh rate. When run app1 only, we can see that the app1 frame rate is 50Hz. When run app2 only, we can see the app2 frame rate is 60Hz.


However if we run both app1 and app2, the framerate of app1 and app2 are both 50Hz no matter which app is started first. The app2 is synced with fb0 but not fb2. This is incorrect.


For example:
Step 1) Run app2. And we can see the frame rate of app2 is 60Hz.
Step 2) Run app1. Now the frame rate of app2 changes to 50Hz.


Please help on how to fix this issue. Thanks!