| From 0cbd0adc4429930567083d18cc8c0fbc5f635d96 Mon Sep 17 00:00:00 2001 |
| From: Mario Kleiner <mario.kleiner.de@gmail.com> |
| Date: Thu, 18 Apr 2019 08:01:57 +0200 |
| Subject: drm: Fix timestamp docs for variable refresh properties. |
| |
| 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.kleiner.de@gmail.com |
| 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. |
| */ |
| |
| /** |