drm/edid: Add secondary GTF curve support

Before CVT-R, some monitors would advertise support for an alternative
GTF formula with lower blanking intervals.  Correctly identify such
monitors, and use the alternative formula when generating modes for
them.

Note that we only do this for "standard" timing descriptors (tuples of
hsize in characters / aspect ratio / vertical refresh).  Range-based
mode lists still only refer to the primary GTF curve.  It would be
possible to do better for the latter case, but monitors are required to
support the primary curve over the entire advertised range, so all it
would win you is a lower pixel clock and therefore possibly better image
quality on analog links.

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

1 files changed, 92 insertions, 27 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 6e999bd..3924a7b 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -64,7 +64,8 @@
 
 #define LEVEL_DMT	0
 #define LEVEL_GTF	1
-#define LEVEL_CVT	2
+#define LEVEL_GTF2	2
+#define LEVEL_CVT	3
 
 static struct edid_quirk {
 	char *vendor;
@@ -713,6 +714,71 @@ drm_monitor_supports_rb(struct edid *edid)
 	return ((edid->input & DRM_EDID_INPUT_DIGITAL) != 0);
 }
 
+static void
+find_gtf2(struct detailed_timing *t, void *data)
+{
+	u8 *r = (u8 *)t;
+	if (r[3] == EDID_DETAIL_MONITOR_RANGE && r[10] == 0x02)
+		*(u8 **)data = r;
+}
+
+/* Secondary GTF curve kicks in above some break frequency */
+static int
+drm_gtf2_hbreak(struct edid *edid)
+{
+	u8 *r = NULL;
+	drm_for_each_detailed_block((u8 *)edid, find_gtf2, &r);
+	return r ? (r[12] * 2) : 0;
+}
+
+static int
+drm_gtf2_2c(struct edid *edid)
+{
+	u8 *r = NULL;
+	drm_for_each_detailed_block((u8 *)edid, find_gtf2, &r);
+	return r ? r[13] : 0;
+}
+
+static int
+drm_gtf2_m(struct edid *edid)
+{
+	u8 *r = NULL;
+	drm_for_each_detailed_block((u8 *)edid, find_gtf2, &r);
+	return r ? (r[15] << 8) + r[14] : 0;
+}
+
+static int
+drm_gtf2_k(struct edid *edid)
+{
+	u8 *r = NULL;
+	drm_for_each_detailed_block((u8 *)edid, find_gtf2, &r);
+	return r ? r[16] : 0;
+}
+
+static int
+drm_gtf2_2j(struct edid *edid)
+{
+	u8 *r = NULL;
+	drm_for_each_detailed_block((u8 *)edid, find_gtf2, &r);
+	return r ? r[17] : 0;
+}
+
+/**
+ * standard_timing_level - get std. timing level(CVT/GTF/DMT)
+ * @edid: EDID block to scan
+ */
+static int standard_timing_level(struct edid *edid)
+{
+	if (edid->revision >= 2) {
+		if (edid->revision >= 4 && (edid->features & DRM_EDID_FEATURE_DEFAULT_GTF))
+			return LEVEL_CVT;
+		if (drm_gtf2_hbreak(edid))
+			return LEVEL_GTF2;
+		return LEVEL_GTF;
+	}
+	return LEVEL_DMT;
+}
+
 /*
  * 0 is reserved.  The spec says 0x01 fill for unused timings.  Some old
  * monitors fill with ascii space (0x20) instead.
@@ -734,8 +800,8 @@ bad_std_timing(u8 a, u8 b)
  * and convert them into a real mode using CVT/GTF/DMT.
  */
 static struct drm_display_mode *
-drm_mode_std(struct drm_connector *connector, struct std_timing *t,
-	     int revision, int timing_level)
+drm_mode_std(struct drm_connector *connector, struct edid *edid,
+	     struct std_timing *t, int revision)
 {
 	struct drm_device *dev = connector->dev;
 	struct drm_display_mode *m, *mode = NULL;
@@ -745,6 +811,7 @@ drm_mode_std(struct drm_connector *connector, struct std_timing *t,
 		>> EDID_TIMING_ASPECT_SHIFT;
 	unsigned vfreq = (t->vfreq_aspect & EDID_TIMING_VFREQ_MASK)
 		>> EDID_TIMING_VFREQ_SHIFT;
+	int timing_level = standard_timing_level(edid);
 
 	if (bad_std_timing(t->hsize, t->vfreq_aspect))
 		return NULL;
@@ -806,6 +873,23 @@ drm_mode_std(struct drm_connector *connector, struct std_timing *t,
 	case LEVEL_GTF:
 		mode = drm_gtf_mode(dev, hsize, vsize, vrefresh_rate, 0, 0);
 		break;
+	case LEVEL_GTF2:
+		/*
+		 * This is potentially wrong if there's ever a monitor with
+		 * more than one ranges section, each claiming a different
+		 * secondary GTF curve.  Please don't do that.
+		 */
+		mode = drm_gtf_mode(dev, hsize, vsize, vrefresh_rate, 0, 0);
+		if (drm_mode_hsync(mode) > drm_gtf2_hbreak(edid)) {
+			kfree(mode);
+			mode = drm_gtf_mode_complex(dev, hsize, vsize,
+						    vrefresh_rate, 0, 0,
+						    drm_gtf2_m(edid),
+						    drm_gtf2_2c(edid),
+						    drm_gtf2_k(edid),
+						    drm_gtf2_2j(edid));
+		}
+		break;
 	case LEVEL_CVT:
 		mode = drm_cvt_mode(dev, hsize, vsize, vrefresh_rate, 0, 0,
 				    false);
@@ -1042,19 +1126,6 @@ static int add_established_modes(struct drm_connector *connector, struct edid *e
 
 	return modes;
 }
-/**
- * stanard_timing_level - get std. timing level(CVT/GTF/DMT)
- * @edid: EDID block to scan
- */
-static int standard_timing_level(struct edid *edid)
-{
-	if (edid->revision >= 2) {
-		if (edid->revision >= 4 && (edid->features & DRM_EDID_FEATURE_DEFAULT_GTF))
-			return LEVEL_CVT;
-		return LEVEL_GTF;
-	}
-	return LEVEL_DMT;
-}
 
 /**
  * add_standard_modes - get std. modes from EDID and add them
@@ -1066,15 +1137,13 @@ static int standard_timing_level(struct edid *edid)
 static int add_standard_modes(struct drm_connector *connector, struct edid *edid)
 {
 	int i, modes = 0;
-	int timing_level;
-
-	timing_level = standard_timing_level(edid);
 
 	for (i = 0; i < EDID_STD_TIMINGS; i++) {
 		struct drm_display_mode *newmode;
 
-		newmode = drm_mode_std(connector, &edid->standard_timings[i],
-				       edid->revision, timing_level);
+		newmode = drm_mode_std(connector, edid,
+				       &edid->standard_timings[i],
+				       edid->revision);
 		if (newmode) {
 			drm_mode_probed_add(connector, newmode);
 			modes++;
@@ -1140,9 +1209,6 @@ range_pixel_clock(struct edid *edid, u8 *t)
 	return t[9] * 10000 + 5001;
 }
 
-/*
- * XXX fix this for GTF secondary curve formula
- */
 static bool
 mode_in_range(struct drm_display_mode *mode, struct edid *edid,
 	      struct detailed_timing *timing)
@@ -1339,7 +1405,6 @@ static int add_detailed_modes(struct drm_connector *connector,
 {
 	int i, modes = 0;
 	struct detailed_non_pixel *data = &timing->data.other_data;
-	int timing_level = standard_timing_level(edid);
 	int gtf = (edid->features & DRM_EDID_FEATURE_DEFAULT_GTF);
 	struct drm_display_mode *newmode;
 	struct drm_device *dev = connector->dev;
@@ -1370,8 +1435,8 @@ static int add_detailed_modes(struct drm_connector *connector,
 			struct drm_display_mode *newmode;
 
 			std = &data->data.timings[i];
-			newmode = drm_mode_std(connector, std, edid->revision,
-					       timing_level);
+			newmode = drm_mode_std(connector, edid, std,
+					       edid->revision);
 			if (newmode) {
 				drm_mode_probed_add(connector, newmode);
 				modes++;