[PATCH v3] drm/i915/dp: Fix VSC dynamic range signaling for RGB formats

[Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>]

For RGB, set dynamic_range to CTA or VESA based on
crtc_state->limited_color_range so sinks apply correct
quantization. YCbCr remains limited (CTA) range.
(DP v1.4, Table 5-1)

v2:
- Added Reported-by and Tested-by tags

v3:
- Add back YCbCr comment(Suraj)

Cc: stable@vger.kernel.org #v5.8+
Reported-by: DeepChirp <DeepChirp@outlook.com>
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/15874
Tested-by: DeepChirp <DeepChirp@outlook.com>
Fixes: 9799c4c3b76e ("drm/i915/dp: Add compute routine for DP VSC SDP")
Assisted-by: GitHub Copilot (GPT-5.4)
Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 98df93884e9a..c1279afe0224 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -3163,8 +3163,13 @@ static void intel_dp_compute_vsc_colorimetry(const struct intel_crtc_state *crtc
 	drm_WARN_ON(display->drm,
 		    vsc->bpc == 6 && vsc->pixelformat != DP_PIXELFORMAT_RGB);
 
-	/* all YCbCr are always limited range */
-	vsc->dynamic_range = DP_DYNAMIC_RANGE_CTA;
+	if (vsc->pixelformat == DP_PIXELFORMAT_RGB)
+		vsc->dynamic_range = crtc_state->limited_color_range ?
+			DP_DYNAMIC_RANGE_CTA : DP_DYNAMIC_RANGE_VESA;
+	/* All YCbCr formats are always limited range. */
+	else
+		vsc->dynamic_range = DP_DYNAMIC_RANGE_CTA;
+
 	vsc->content_type = DP_CONTENT_TYPE_NOT_DEFINED;
 }
 
-- 
2.25.1