From: Mario Kleiner mario.kleiner.de@gmail.com
commit 0cbd0adc4429930567083d18cc8c0fbc5f635d96 upstream.
As discussed with Nicholas and Daniel Vetter (patchwork link to discussion below), the VRR timestamping behaviour produced utterly useless and bogus vblank/pageflip timestamps. We have found a way to fix this and provide sane behaviour.
As of Linux 5.2, the amdgpu driver will be able to provide exactly the same vblank / pageflip timestamp semantic in variable refresh rate mode as in standard fixed refresh rate mode. This is achieved by deferring core vblank handling (drm_crtc_handle_vblank()) until the end of front porch, and also defer the sending of pageflip completion events until end of front porch, when we can safely compute correct pageflip/vblank timestamps.
The same approach will be possible for other VRR capable kms drivers, so we can actually have sane and useful timestamps in VRR mode.
This patch removes the section of the docs that describes the broken timestamp behaviour present in Linux 5.0/5.1.
Fixes: ab7a664f7a2d ("drm: Document variable refresh properties") Link: https://patchwork.freedesktop.org/patch/285333/ Acked-by: Daniel Vetter daniel.vetter@ffwll.ch Reviewed-by: Nicholas Kazlauskas nicholas.kazlauskas@amd.com Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Link: https://patchwork.freedesktop.org/patch/msgid/20190418060157.18968-1-mario.k... Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/drm_connector.c | 6 ------ 1 file changed, 6 deletions(-)
--- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -1385,12 +1385,6 @@ EXPORT_SYMBOL(drm_mode_create_scaling_mo * * The driver may place further restrictions within these minimum * and maximum bounds. - * - * The semantics for the vertical blank timestamp differ when - * variable refresh rate is active. The vertical blank timestamp - * is defined to be an estimate using the current mode's fixed - * refresh rate timings. The semantics for the page-flip event - * timestamp remain the same. */
/**