drm/edid: Decode 3-byte CVT codes from EDID 1.4

Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_edid.c

@@ -897,6 +897,51 @@ static int drm_gtf_modes_for_range(struct drm_connector *connector,
 	return modes;
 }
 
+static int drm_cvt_modes(struct drm_connector *connector,
+			 struct detailed_timing *timing)
+{
+	int i, j, modes = 0;
+	struct drm_display_mode *newmode;
+	struct drm_device *dev = connector->dev;
+	struct cvt_timing *cvt;
+	const int rates[] = { 60, 85, 75, 60, 50 };
+
+	for (i = 0; i < 4; i++) {
+		int width, height;
+		cvt = &(timing->data.other_data.data.cvt[i]);
+
+		height = (cvt->code[0] + ((cvt->code[1] & 0xf0) << 8) + 1) * 2;
+		switch (cvt->code[1] & 0xc0) {
+		case 0x00:
+			width = height * 4 / 3;
+			break;
+		case 0x40:
+			width = height * 16 / 9;
+			break;
+		case 0x80:
+			width = height * 16 / 10;
+			break;
+		case 0xc0:
+			width = height * 15 / 9;
+			break;
+		}
+
+		for (j = 1; j < 5; j++) {
+			if (cvt->code[2] & (1 << j)) {
+				newmode = drm_cvt_mode(dev, width, height,
+						       rates[j], j == 0,
+						       false, false);
+				if (newmode) {
+					drm_mode_probed_add(connector, newmode);
+					modes++;
+				}
+			}
+		}
+	}
+
+	return modes;
+}
+
 static int add_detailed_modes(struct drm_connector *connector,
 			      struct detailed_timing *timing,
 			      struct edid *edid, u32 quirks, int preferred)
@@ -941,6 +986,9 @@ static int add_detailed_modes(struct drm_connector *connector,
 			}
 		}
 		break;
+	case EDID_DETAIL_CVT_3BYTE:
+		modes += drm_cvt_modes(connector, timing);
+		break;
 	default:
 		break;
 	}

include/drm/drm_edid.h

@@ -106,6 +106,10 @@ struct detailed_data_color_point {
 	u8 wpindex2[3];
 } __attribute__((packed));
 
+struct cvt_timing {
+	u8 code[3];
+} __attribute__((packed));
+
 struct detailed_non_pixel {
 	u8 pad1;
 	u8 type; /* ff=serial, fe=string, fd=monitor range, fc=monitor name
@@ -117,6 +121,7 @@ struct detailed_non_pixel {
 		struct detailed_data_monitor_range range;
 		struct detailed_data_wpindex color;
 		struct std_timing timings[5];
+		struct cvt_timing cvt[4];
 	} data;
 } __attribute__((packed));