2016-12-05 12:01 GMT+01:00 Bartosz Golaszewski bgolaszewski@baylibre.com:
Hi Jyri,
I pulled your recent tilcdc pull request on top of v4.9 and Sekhar's davinci branch (+ vga dac DT)[1].
I'm getting "vblank wait timed out" errors when running simple modetest[2].
This error happened before with the drm_bridge series[3], but went away at one of the subsequent patch versions.
Could you please verify that you see the same error and advise on what could be the reason? I'm investigating on my own as well.
Best regards, Bartosz Golaszewski
[1] https://github.com/brgl/linux/tree/tilcdc/modetest_error [2] http://pastebin.com/rCM44Uds [3] http://www.spinics.net/lists/dri-devel/msg123732.html
This seems like some END_OF_FRAME0 interrupt-related race condition. Increasing the timeout in drm_atomic_helper_wait_for_vblanks() from 50 to 100 and dropping drm_modeset_lock_crtc()/drm_modeset_unlock_crtc() in tilcdc_crtc_recover_work() makes the warning disappear. Also: calling drm_crtc_vblank_off() additionally before locking the crtc in tilcdc_crtc_recover_work() also seems to fix the issue 90% of times. I have been unable to figure out a reliable solution today though.
Best regards, Bartosz Golaszewski