[PATCH] drm/display/dp: Default 8 bpc support when DSC is supported

[Ankit Nautiyal]

As per DP v1.4, a DP DSC Sink device shall support 8bpc in DPCD 6Ah.
Apparently some panels that do support DSC, are not setting the bit for
8bpc.

So always assume 8bpc support by DSC decoder, when DSC is claimed to be
supported.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/display/drm_dp_helper.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
index e6a78fd32380..0aa4ce17420c 100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -2447,14 +2447,19 @@ int drm_dp_dsc_sink_supported_input_bpcs(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_S
 					 u8 dsc_bpc[3])
 {
 	int num_bpc = 0;
+
+	if (!dsc_dpcd[DP_DSC_SUPPORT] & DP_DSC_DECOMPRESSION_IS_SUPPORTED)
+		return 0;
+
 	u8 color_depth = dsc_dpcd[DP_DSC_DEC_COLOR_DEPTH_CAP - DP_DSC_SUPPORT];
 
 	if (color_depth & DP_DSC_12_BPC)
 		dsc_bpc[num_bpc++] = 12;
 	if (color_depth & DP_DSC_10_BPC)
 		dsc_bpc[num_bpc++] = 10;
-	if (color_depth & DP_DSC_8_BPC)
-		dsc_bpc[num_bpc++] = 8;
+
+	/* A DP DSC Sink devices shall support 8 bpc. */
+	dsc_bpc[num_bpc++] = 8;
 
 	return num_bpc;
 }
-- 
2.40.1