drm/intel/display: Add support for pipe background color (v4)

Gen9 platforms allow CRTC's to be programmed with a background/canvas
color below the programmable planes.  Let's expose this as a property to
allow userspace to program a desired value.

This patch is based on earlier work by Chandra Konduru and Matt Roper.
Between 2018 and now, intel/display has changed so much that another
rewrite was necessary.

v2:
 - Set initial background color (black) via proper helper function (Bob)
 - Fix debugfs output
 - General rebasing
v3 (Maarten):
 - Rebase on top of recent changes.
v4 (Maarten):
 - Complete rewrite based on the solution that went upstream, and
   on the new intel color management features.

Cc: Chandra Konduru <chandra.konduru@intel.com>
Cc: dri-devel@lists.freedesktop.org
Co-developed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Link: https://patch.msgid.link/20260505200133.636584-2-dev@lankhorst.se
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
index 81bef000a4e3..3d6f36773ad8 100644
--- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
+++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
@@ -572,6 +572,12 @@ static void intel_crtc_info(struct seq_file *m, struct intel_crtc *crtc)
 
 	intel_scaler_info(m, crtc);
 
+	if (DISPLAY_VER(display) >= 9) {
+		u32 background = crtc_state->hw.background_color;
+
+		seq_printf(m, "\tbackground color (10bpc XRGB2101010): %08x\n", background);
+	}
+
 	if (crtc_state->joiner_pipes)
 		seq_printf(m, "\tLinked to 0x%x pipes as a %s\n",
 			   crtc_state->joiner_pipes,