[Intel-gfx] [PATCH] drm/drm_edid: Refactor HFVSDB parsing for DSC1.2

[Ankit Nautiyal]

DSC capabilities are given in bytes 11-13 of VSDB (i.e. bytes 8-10 of
SCDS). Since minimum length of Data block is 7, all bytes greater than 7
must be read only after checking the length of the data block.

This patch adds check for data block length before reading relavant DSC
bytes. It also corrects min DSC BPC to 8, and minor refactoring for
better readability, and proper log messages.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/drm_edid.c | 124 +++++++++++++++++++++++--------------
 1 file changed, 77 insertions(+), 47 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index bbc25e3b7220..f683a8d5fd31 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -5703,12 +5703,58 @@ static void drm_parse_ycbcr420_deep_color_info(struct drm_connector *connector,
 	hdmi->y420_dc_modes = dc_mask;
 }
 
+static void drm_parse_dsc_slice_info(u8 dsc_max_slices,
+				     struct drm_hdmi_dsc_cap *hdmi_dsc)
+{
+	switch (dsc_max_slices) {
+	case 1:
+		hdmi_dsc->max_slices = 1;
+		hdmi_dsc->clk_per_slice = 340;
+		break;
+	case 2:
+		hdmi_dsc->max_slices = 2;
+		hdmi_dsc->clk_per_slice = 340;
+		break;
+	case 3:
+		hdmi_dsc->max_slices = 4;
+		hdmi_dsc->clk_per_slice = 340;
+		break;
+	case 4:
+		hdmi_dsc->max_slices = 8;
+		hdmi_dsc->clk_per_slice = 340;
+		break;
+	case 5:
+		hdmi_dsc->max_slices = 8;
+		hdmi_dsc->clk_per_slice = 400;
+		break;
+	case 6:
+		hdmi_dsc->max_slices = 12;
+		hdmi_dsc->clk_per_slice = 400;
+		break;
+	case 7:
+		hdmi_dsc->max_slices = 16;
+		hdmi_dsc->clk_per_slice = 400;
+		break;
+	case 0:
+	default:
+		hdmi_dsc->max_slices = 0;
+		hdmi_dsc->clk_per_slice = 0;
+	}
+}
+
 /* Sink Capability Data Structure */
 static void drm_parse_hdmi_forum_scds(struct drm_connector *connector,
 				      const u8 *hf_scds)
 {
 	struct drm_display_info *display = &connector->display_info;
 	struct drm_hdmi_info *hdmi = &display->hdmi;
+	u8 db_length = hf_scds[0] & 0x1F;
+	u8 dsc_max_frl_rate;
+	u8 dsc_max_slices;
+	struct drm_hdmi_dsc_cap *hdmi_dsc = &hdmi->dsc_cap;
+
+	if (db_length < 7 || db_length > 31)
+		return;
 
 	display->has_hdmi_infoframe = true;
 
@@ -5749,17 +5795,25 @@ static void drm_parse_hdmi_forum_scds(struct drm_connector *connector,
 
 	if (hf_scds[7]) {
 		u8 max_frl_rate;
-		u8 dsc_max_frl_rate;
-		u8 dsc_max_slices;
-		struct drm_hdmi_dsc_cap *hdmi_dsc = &hdmi->dsc_cap;
 
-		DRM_DEBUG_KMS("hdmi_21 sink detected. parsing edid\n");
 		max_frl_rate = (hf_scds[7] & DRM_EDID_MAX_FRL_RATE_MASK) >> 4;
+		if (max_frl_rate)
+			DRM_DEBUG_KMS("HDMI2.1 FRL support detected\n");
+
 		drm_get_max_frl_rate(max_frl_rate, &hdmi->max_lanes,
 				     &hdmi->max_frl_rate_per_lane);
+
+		drm_parse_ycbcr420_deep_color_info(connector, hf_scds);
+	}
+
+	if (db_length < 11)
+		return;
+
+	if (hf_scds[11]) {
 		hdmi_dsc->v_1p2 = hf_scds[11] & DRM_EDID_DSC_1P2;
 
 		if (hdmi_dsc->v_1p2) {
+			DRM_DEBUG_KMS("HDMI DSC1.2 support detected\n");
 			hdmi_dsc->native_420 = hf_scds[11] & DRM_EDID_DSC_NATIVE_420;
 			hdmi_dsc->all_bpp = hf_scds[11] & DRM_EDID_DSC_ALL_BPP;
 
@@ -5770,52 +5824,28 @@ static void drm_parse_hdmi_forum_scds(struct drm_connector *connector,
 			else if (hf_scds[11] & DRM_EDID_DSC_10BPC)
 				hdmi_dsc->bpc_supported = 10;
 			else
-				hdmi_dsc->bpc_supported = 0;
-
-			dsc_max_frl_rate = (hf_scds[12] & DRM_EDID_DSC_MAX_FRL_RATE_MASK) >> 4;
-			drm_get_max_frl_rate(dsc_max_frl_rate, &hdmi_dsc->max_lanes,
-					     &hdmi_dsc->max_frl_rate_per_lane);
-			hdmi_dsc->total_chunk_kbytes = hf_scds[13] & DRM_EDID_DSC_TOTAL_CHUNK_KBYTES;
-
-			dsc_max_slices = hf_scds[12] & DRM_EDID_DSC_MAX_SLICES;
-			switch (dsc_max_slices) {
-			case 1:
-				hdmi_dsc->max_slices = 1;
-				hdmi_dsc->clk_per_slice = 340;
-				break;
-			case 2:
-				hdmi_dsc->max_slices = 2;
-				hdmi_dsc->clk_per_slice = 340;
-				break;
-			case 3:
-				hdmi_dsc->max_slices = 4;
-				hdmi_dsc->clk_per_slice = 340;
-				break;
-			case 4:
-				hdmi_dsc->max_slices = 8;
-				hdmi_dsc->clk_per_slice = 340;
-				break;
-			case 5:
-				hdmi_dsc->max_slices = 8;
-				hdmi_dsc->clk_per_slice = 400;
-				break;
-			case 6:
-				hdmi_dsc->max_slices = 12;
-				hdmi_dsc->clk_per_slice = 400;
-				break;
-			case 7:
-				hdmi_dsc->max_slices = 16;
-				hdmi_dsc->clk_per_slice = 400;
-				break;
-			case 0:
-			default:
-				hdmi_dsc->max_slices = 0;
-				hdmi_dsc->clk_per_slice = 0;
-			}
+				/* Supports min 8 BPC if DSC1.2 is supported*/
+				hdmi_dsc->bpc_supported = 8;
 		}
 	}
 
-	drm_parse_ycbcr420_deep_color_info(connector, hf_scds);
+	if (db_length < 12)
+		return;
+
+	if (hdmi_dsc->v_1p2 && hf_scds[12]) {
+		dsc_max_slices = hf_scds[12] & DRM_EDID_DSC_MAX_SLICES;
+		drm_parse_dsc_slice_info(dsc_max_slices, hdmi_dsc);
+
+		dsc_max_frl_rate = (hf_scds[12] & DRM_EDID_DSC_MAX_FRL_RATE_MASK) >> 4;
+		drm_get_max_frl_rate(dsc_max_frl_rate, &hdmi_dsc->max_lanes,
+				     &hdmi_dsc->max_frl_rate_per_lane);
+	}
+
+	if (db_length < 13)
+		return;
+
+	if (hdmi_dsc->v_1p2 && hf_scds[13])
+		hdmi_dsc->total_chunk_kbytes = hf_scds[13] & DRM_EDID_DSC_TOTAL_CHUNK_KBYTES;
 }
 
 static void drm_parse_hdmi_deep_color_info(struct drm_connector *connector,
-- 
2.25.1