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>

2 files changed, 53 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index cc8e6968271..30af8f3e642 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/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;
         }
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 9087557fd83..d33c3e03860 100644
--- a/include/drm/drm_edid.h
+++ b/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));