[PATCH 09/11] drm/i915: Program DB LUT registers before vblank

[Chaitanya Kumar Borah]

Double Buffered LUT registers can be programmed in the active region.
This patch implements the MMIO path for it. Program the registers after
evading vblank. The HW latches on to the registers after delayed vblank.
It takes around 1024 cdclk cycles(~one scanline) for this.

Following assumptions have been made while making this change

 - Current vblank evasion time is sufficient for programming
   the LUT registers.
 - Current guardband calculation would be sufficient for the HW
   to latch on to the new values

Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 85e28b4c9e66..df9c992d2939 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -6725,10 +6725,12 @@ static void intel_pre_update_crtc(struct intel_atomic_state *state,
 static void intel_update_crtc(struct intel_atomic_state *state,
 			      struct intel_crtc *crtc)
 {
+	struct intel_display *display = to_intel_display(crtc);
 	const struct intel_crtc_state *old_crtc_state =
 		intel_atomic_get_old_crtc_state(state, crtc);
 	struct intel_crtc_state *new_crtc_state =
 		intel_atomic_get_new_crtc_state(state, crtc);
+	bool modeset = intel_crtc_needs_modeset(new_crtc_state);
 
 	if (new_crtc_state->use_dsb) {
 		intel_crtc_prepare_vblank_event(new_crtc_state, &crtc->dsb_event);
@@ -6738,6 +6740,12 @@ static void intel_update_crtc(struct intel_atomic_state *state,
 		/* Perform vblank evasion around commit operation */
 		intel_pipe_update_start(state, crtc);
 
+		if (!modeset &&
+		    intel_crtc_needs_color_update(new_crtc_state) &&
+		    !new_crtc_state->dsb_color &&
+		    HAS_DOUBLE_BUFFERED_LUT(display))
+			intel_color_load_luts(new_crtc_state);
+
 		if (new_crtc_state->dsb_commit)
 			intel_dsb_commit(new_crtc_state->dsb_commit, false);
 
-- 
2.25.1