openwrt/target/linux/bcm27xx/patches-5.15/950-0562-drm-Check-whether-the-gamma-lut-has-changed-before-u.patch

From 190eaf4f8d95196b1b66c7c356d28643a6355039 Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Tue, 2 Nov 2021 16:01:36 +0000
Subject: [PATCH] drm: Check whether the gamma lut has changed before
 updating

drm_crtc_legacy_gamma_set updates the gamma_lut blob unconditionally,
which leads to unnecessary reprogramming of hardware.

Check whether the blob contents has actually changed before
signalling that it has been updated.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
 drivers/gpu/drm/drm_color_mgmt.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_color_mgmt.c
+++ b/drivers/gpu/drm/drm_color_mgmt.c
@@ -326,8 +326,12 @@ static int drm_crtc_legacy_gamma_set(str
 	replaced = drm_property_replace_blob(&crtc_state->degamma_lut,
 					     use_gamma_lut ? NULL : blob);
 	replaced |= drm_property_replace_blob(&crtc_state->ctm, NULL);
-	replaced |= drm_property_replace_blob(&crtc_state->gamma_lut,
+	if (!crtc_state->gamma_lut || !crtc_state->gamma_lut->data ||
+	    memcmp(crtc_state->gamma_lut->data, blob_data, blob->length))
+		replaced |= drm_property_replace_blob(&crtc_state->gamma_lut,
 					      use_gamma_lut ? blob : NULL);
+	else
+		drm_property_blob_put(blob);
 	crtc_state->color_mgmt_changed |= replaced;
 
 	ret = drm_atomic_commit(state);