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/ Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com --- drivers/gpu/drm/drm_connector.c | 6 ------ 1 file changed, 6 deletions(-)
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index 2355124849db..b34c3d38bf15 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -1416,12 +1416,6 @@ EXPORT_SYMBOL(drm_mode_create_scaling_mode_property); * * 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. */
/**
On Thu, Apr 18, 2019 at 08:01:57AM +0200, Mario Kleiner wrote:
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/ Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com
drivers/gpu/drm/drm_connector.c | 6 ------ 1 file changed, 6 deletions(-)
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index 2355124849db..b34c3d38bf15 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -1416,12 +1416,6 @@ EXPORT_SYMBOL(drm_mode_create_scaling_mode_property);
- 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.
Yay! Thanks for all your work to polish VRR in linux.
Acked-by: Daniel Vetter daniel.vetter@ffwll.ch
*/
/**
2.20.1
On 4/18/19 2:01 AM, Mario Kleiner wrote:
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/ Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com
Reviewed-by: Nicholas Kazlauskas nicholas.kazlauskas@amd.com
Someone else can feel free to push this as I don't have commit rights for DRM.
Thanks!
Nicholas Kazlauskas
drivers/gpu/drm/drm_connector.c | 6 ------ 1 file changed, 6 deletions(-)
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index 2355124849db..b34c3d38bf15 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -1416,12 +1416,6 @@ EXPORT_SYMBOL(drm_mode_create_scaling_mode_property);
- 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.
*/
/**
Nag nag: The below documentation patch, acked-by Daniel and r-b'd by Nicholas seems to not have made it into drm-next yet?
thanks, -mario
On Thu, Apr 18, 2019 at 2:45 PM Kazlauskas, Nicholas Nicholas.Kazlauskas@amd.com wrote:
On 4/18/19 2:01 AM, Mario Kleiner wrote:
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/ Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com
Reviewed-by: Nicholas Kazlauskas nicholas.kazlauskas@amd.com
Someone else can feel free to push this as I don't have commit rights for DRM.
Thanks!
Nicholas Kazlauskas
drivers/gpu/drm/drm_connector.c | 6 ------ 1 file changed, 6 deletions(-)
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index 2355124849db..b34c3d38bf15 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -1416,12 +1416,6 @@ EXPORT_SYMBOL(drm_mode_create_scaling_mode_property);
- 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.
*/
/**
On Tue, May 7, 2019 at 1:15 AM Mario Kleiner mario.kleiner.de@gmail.com wrote:
Nag nag: The below documentation patch, acked-by Daniel and r-b'd by Nicholas seems to not have made it into drm-next yet?
Pushed to drm-misc-next-fixes
Thanks!
Alex
thanks, -mario
On Thu, Apr 18, 2019 at 2:45 PM Kazlauskas, Nicholas Nicholas.Kazlauskas@amd.com wrote:
On 4/18/19 2:01 AM, Mario Kleiner wrote:
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/ Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com
Reviewed-by: Nicholas Kazlauskas nicholas.kazlauskas@amd.com
Someone else can feel free to push this as I don't have commit rights for DRM.
Thanks!
Nicholas Kazlauskas
drivers/gpu/drm/drm_connector.c | 6 ------ 1 file changed, 6 deletions(-)
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index 2355124849db..b34c3d38bf15 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -1416,12 +1416,6 @@ EXPORT_SYMBOL(drm_mode_create_scaling_mode_property);
- 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.
*/
/**
dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
dri-devel@lists.freedesktop.org
-
Alex Deucher -
Daniel Vetter -
Kazlauskas, Nicholas -
Mario Kleiner