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

[Mario Kleiner <mario.kleiner.de@gmail.com>]

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 <mario.kleiner.de@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 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 b/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 =
 			to_intel_crtc_state(crtc->state);
-		bool update_pipe = !modeset && pipe_config->update_pipe;
 
 		if (modeset && crtc->state->active) {
 			update_scanline_offset(to_intel_crtc(crtc));
@@ -13699,8 +13698,7 @@ static int intel_atomic_commit(struct drm_device *dev,
 		    drm_atomic_get_existing_plane_state(state, crtc->primary))
 			intel_fbc_enable(intel_crtc);
 
-		if (crtc->state->active &&
-		    (crtc->state->planes_changed || update_pipe))
+		if (crtc->state->active)
 			drm_atomic_helper_commit_planes_on_crtc(old_crtc_state);
 
 		if (pipe_config->base.active && needs_vblank_wait(pipe_config))
-- 
2.7.0