Re: [PATCH] drm/i915: Fix legacy gamma lut updates in Linux 4.7-rc6

From: Lionel Landwerlin
Date: Tue Jul 12 2016 - 11:03:02 EST

On 12/07/16 13:11, Mario Kleiner wrote:
On 07/12/2016 12:50 PM, Lionel Landwerlin wrote:
Hi Mario,

Hi Lionel,

There was a couple of patch to fix this issue :

Looking at them they should fix the issue, but they seem to be stuck in review?

I tested this late last week on drm-intel-nightly, it seems a series of
revert fixed most of the issues.

You mean something else has fixed legacy gamma updates, as i can't find above patches applied on drm-intel-nightly?

This revert on drm-intel-nightly seems to have fixed the problem :

Are those fixes supposed to be already part of 4.7-rc7, the final rc afaik?

I haven't seen it on 4.7-rc7.




On 12/07/16 11:33, Mario Kleiner wrote:
Updating legacy gamma tables, e.g., via RandR doesn't work at all
as of Linux 4.7-rc6.

Reason seems to be that the required call to
drm_atomic_helper_commit_planes_on_crtc is skipped in
intel_atomic_commit after userspace set new gamma tables,
because neither crtc->state->planes_changed nor
update_pipe (= pipe_config->update_pipe) are true.

Removing the check for planes_changed || update_pipe fixes
gamma table updates.

The code for Linux 4.8 drm-next has changed a lot in that area
wrt. 4.7, but the new code for 4.8 also removed those checks
and calls drm_atomic_helper_commit_planes_on_crtc unconditionally,
and legacy gamma lut updates work on drm-next, so this seems to be
the right solution.

Tested also shutdown/reboot, suspend/resume, (un-)plugging displays,
mode switches for resolution/refresh rate, display rotation, and
page-flipping/pageflip timing on Intel HD Ironlake to confirm the
fix apparently doesn't break anything under X11.

Signed-off-by: Mario Kleiner <>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
drivers/gpu/drm/i915/intel_display.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c
index 04452cf..eb8fb36 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -13685,7 +13685,6 @@ static int intel_atomic_commit(struct
drm_device *dev,
bool modeset = needs_modeset(crtc->state);
struct intel_crtc_state *pipe_config =
- bool update_pipe = !modeset && pipe_config->update_pipe;
if (modeset && crtc->state->active) {
@@ -13699,8 +13698,7 @@ static int intel_atomic_commit(struct
drm_device *dev,
drm_atomic_get_existing_plane_state(state, crtc->primary))
- if (crtc->state->active &&
- (crtc->state->planes_changed || update_pipe))
+ if (crtc->state->active)
if (pipe_config-> && needs_vblank_wait(pipe_config))