[PATCH 1/2] drm: Add a detailed DP HDMI branch info on debugfs

[Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx>]

When DP downstream has HDMI branch, it checks below functionality and
shows supports. It follows DP 1.4a spec; Table 2-161: Address Mapping
within DPCD Receiver Capability Field (DPCD Addresses 00000h
through 000FFh).

Added flags for DP downstream:
YCBCR422_PASS_THROUGH_SUPPORT, YCBCR420_PASS_THROUGH_SUPPORT,
CONVERSION_FROM_YCBCR444_TO_YCBCR422_SUPPORT and
CONVERSION_FROM_YCBCR444_TO_YCBCR420_SUPPORT.

Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx>
---
 drivers/gpu/drm/drm_dp_helper.c | 19 +++++++++++++++++++
 include/drm/drm_dp_helper.h     |  5 +++++
 2 files changed, 24 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 5a103e9b3c86..cb6dcfb13127 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -531,6 +531,25 @@ void drm_dp_downstream_debug(struct seq_file *m,
 
 		if (bpc > 0)
 			seq_printf(m, "\t\tMax bpc: %d\n", bpc);
+
+		if (type == DP_DS_PORT_TYPE_HDMI) {
+			bool ycbcr422_passthru = port_cap[3] &
+						 DP_DS_YCBCR422_PASSTHRU_SUPPORT;
+			bool ycbcr420_passthru = port_cap[3] &
+						 DP_DS_YCBCR420_PASSTHRU_SUPPORT;
+			bool ycbcr422_convert = port_cap[3] &
+						DP_DS_CONV_YCBCR444_TO_YCBCR422_SUPPORT;
+			bool ycbcr420_convert = port_cap[3] &
+						DP_DS_CONV_YCBCR444_TO_YCBCR420_SUPPORT;
+			seq_printf(m, "\t\tHDMI YCbCr 4:2:2 pass-through support: %s\n",
+				   ycbcr422_passthru ? "yes" : "no");
+			seq_printf(m, "\t\tHDMI YCbCr 4:2:0  pass-through support: %s\n",
+				   ycbcr420_passthru ? "yes" : "no");
+			seq_printf(m, "\t\tHDMI YCbCr 4:4:4 to YCbCr 4:2:2 Convert support: %s\n",
+				   ycbcr422_convert ? "yes" : "no");
+			seq_printf(m, "\t\tHDMI YCbCr 4:4:4 to YCbCr 4:2:0 Convert support: %s\n",
+				   ycbcr420_convert ? "yes" : "no");
+		}
 	}
 }
 EXPORT_SYMBOL(drm_dp_downstream_debug);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 262faf9e5e94..d61eadaba769 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -391,6 +391,11 @@
 # define DP_DS_10BPC		            1
 # define DP_DS_12BPC		            2
 # define DP_DS_16BPC		            3
+/* offset 3 for HDMI */
+# define DP_DS_YCBCR422_PASSTHRU_SUPPORT    (1 << 1) /* 1.4 */
+# define DP_DS_YCBCR420_PASSTHRU_SUPPORT    (1 << 2)
+# define DP_DS_CONV_YCBCR444_TO_YCBCR422_SUPPORT (1 << 3)
+# define DP_DS_CONV_YCBCR444_TO_YCBCR420_SUPPORT (1 << 4)
 
 #define DP_MAX_DOWNSTREAM_PORTS		    0x10
 
-- 
2.24.1

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