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, 54 insertions, 27 deletions

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 76d63394c77..d460b6c472d 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -276,35 +276,29 @@ struct drm_display_mode *drm_cvt_mode(struct drm_device *dev, int hdisplay,
 EXPORT_SYMBOL(drm_cvt_mode);
 
 /**
- * drm_gtf_mode - create the modeline based on GTF algorithm
+ * drm_gtf_mode_complex - create the modeline based on full GTF algorithm
  *
  * @dev		:drm device
  * @hdisplay	:hdisplay size
  * @vdisplay	:vdisplay size
  * @vrefresh	:vrefresh rate.
  * @interlaced	:whether the interlace is supported
- * @margins	:whether the margin is supported
+ * @margins	:desired margin size
+ * @GTF_[MCKJ]  :extended GTF formula parameters
  *
  * LOCKING.
  * none.
  *
- * return the modeline based on GTF algorithm
- *
- * This function is to create the modeline based on the GTF algorithm.
- * Generalized Timing Formula is derived from:
- *	GTF Spreadsheet by Andy Morrish (1/5/97)
- *	available at http://www.vesa.org
+ * return the modeline based on full GTF algorithm.
  *
- * And it is copied from the file of xserver/hw/xfree86/modes/xf86gtf.c.
- * What I have done is to translate it by using integer calculation.
- * I also refer to the function of fb_get_mode in the file of
- * drivers/video/fbmon.c
+ * GTF feature blocks specify C and J in multiples of 0.5, so we pass them
+ * in here multiplied by two.  For a C of 40, pass in 80.
  */
-struct drm_display_mode *drm_gtf_mode(struct drm_device *dev, int hdisplay,
-				      int vdisplay, int vrefresh,
-				      bool interlaced, int margins)
-{
-	/* 1) top/bottom margin size (% of height) - default: 1.8, */
+struct drm_display_mode *
+drm_gtf_mode_complex(struct drm_device *dev, int hdisplay, int vdisplay,
+		     int vrefresh, bool interlaced, int margins,
+		     int GTF_M, int GTF_2C, int GTF_K, int GTF_2J)
+{	/* 1) top/bottom margin size (% of height) - default: 1.8, */
 #define	GTF_MARGIN_PERCENTAGE		18
 	/* 2) character cell horizontal granularity (pixels) - default 8 */
 #define	GTF_CELL_GRAN			8
@@ -316,17 +310,9 @@ struct drm_display_mode *drm_gtf_mode(struct drm_device *dev, int hdisplay,
 #define H_SYNC_PERCENT			8
 	/* min time of vsync + back porch (microsec) */
 #define MIN_VSYNC_PLUS_BP		550
-	/* blanking formula gradient */
-#define GTF_M				600
-	/* blanking formula offset */
-#define GTF_C				40
-	/* blanking formula scaling factor */
-#define GTF_K				128
-	/* blanking formula scaling factor */
-#define GTF_J				20
 	/* C' and M' are part of the Blanking Duty Cycle computation */
-#define GTF_C_PRIME		(((GTF_C - GTF_J) * GTF_K / 256) + GTF_J)
-#define GTF_M_PRIME		(GTF_K * GTF_M / 256)
+#define GTF_C_PRIME	((((GTF_2C - GTF_2J) * GTF_K / 256) + GTF_2J) / 2)
+#define GTF_M_PRIME	(GTF_K * GTF_M / 256)
 	struct drm_display_mode *drm_mode;
 	unsigned int hdisplay_rnd, vdisplay_rnd, vfieldrate_rqd;
 	int top_margin, bottom_margin;
@@ -470,7 +456,48 @@ struct drm_display_mode *drm_gtf_mode(struct drm_device *dev, int hdisplay,
 
 	return drm_mode;
 }
+EXPORT_SYMBOL(drm_gtf_mode_complex);
+
+/**
+ * drm_gtf_mode - create the modeline based on GTF algorithm
+ *
+ * @dev		:drm device
+ * @hdisplay	:hdisplay size
+ * @vdisplay	:vdisplay size
+ * @vrefresh	:vrefresh rate.
+ * @interlaced	:whether the interlace is supported
+ * @margins	:whether the margin is supported
+ *
+ * LOCKING.
+ * none.
+ *
+ * return the modeline based on GTF algorithm
+ *
+ * This function is to create the modeline based on the GTF algorithm.
+ * Generalized Timing Formula is derived from:
+ *	GTF Spreadsheet by Andy Morrish (1/5/97)
+ *	available at http://www.vesa.org
+ *
+ * And it is copied from the file of xserver/hw/xfree86/modes/xf86gtf.c.
+ * What I have done is to translate it by using integer calculation.
+ * I also refer to the function of fb_get_mode in the file of
+ * drivers/video/fbmon.c
+ *
+ * Standard GTF parameters:
+ * M = 600
+ * C = 40
+ * K = 128
+ * J = 20
+ */
+struct drm_display_mode *
+drm_gtf_mode(struct drm_device *dev, int hdisplay, int vdisplay, int vrefresh,
+	     bool lace, int margins)
+{
+	return drm_gtf_mode_complex(dev, hdisplay, vdisplay, vrefresh, lace,
+				    margins, 600, 40 * 2, 128, 20 * 2);
+}
 EXPORT_SYMBOL(drm_gtf_mode);
+
 /**
  * drm_mode_set_name - set the name on a mode
  * @mode: name will be set in this mode