drm/i915/chv: Use 16 and 32 for low and high drain latency precision.

Current chv spec teels we can only use either 16 or 32 bits as precision.

Although in the past VLV went from 16/32 to 32/64 and spec might not be updated,
these precision values brings stability and fixes some issues Wayne was facing.

Cc: Wayne Boyer <wayne.boyer@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Tested-by: Wayne Boyer <wayne.boyer@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[danvet: Sprinkle const as requested by Ville.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -4054,17 +4054,18 @@ enum punit_power_well {
 #define   DSPFW_PLANEA_WM1_HI_MASK	(1<<0)
 
 /* drain latency register values*/
+#define DRAIN_LATENCY_PRECISION_16	16
 #define DRAIN_LATENCY_PRECISION_32	32
 #define DRAIN_LATENCY_PRECISION_64	64
 #define VLV_DDL(pipe)			(VLV_DISPLAY_BASE + 0x70050 + 4 * (pipe))
-#define DDL_CURSOR_PRECISION_64		(1<<31)
-#define DDL_CURSOR_PRECISION_32		(0<<31)
+#define DDL_CURSOR_PRECISION_HIGH	(1<<31)
+#define DDL_CURSOR_PRECISION_LOW	(0<<31)
 #define DDL_CURSOR_SHIFT		24
-#define DDL_SPRITE_PRECISION_64(sprite)	(1<<(15+8*(sprite)))
-#define DDL_SPRITE_PRECISION_32(sprite)	(0<<(15+8*(sprite)))
+#define DDL_SPRITE_PRECISION_HIGH(sprite)	(1<<(15+8*(sprite)))
+#define DDL_SPRITE_PRECISION_LOW(sprite)	(0<<(15+8*(sprite)))
 #define DDL_SPRITE_SHIFT(sprite)	(8+8*(sprite))
-#define DDL_PLANE_PRECISION_64		(1<<7)
-#define DDL_PLANE_PRECISION_32		(0<<7)
+#define DDL_PLANE_PRECISION_HIGH	(1<<7)
+#define DDL_PLANE_PRECISION_LOW		(0<<7)
 #define DDL_PLANE_SHIFT			0
 #define DRAIN_LATENCY_MASK		0x7f
 

drivers/gpu/drm/i915/intel_pm.c

@@ -1345,6 +1345,7 @@ static bool vlv_compute_drain_latency(struct drm_crtc *crtc,
 				      int *prec_mult,
 				      int *drain_latency)
 {
+	struct drm_device *dev = crtc->dev;
 	int entries;
 	int clock = to_intel_crtc(crtc)->config.adjusted_mode.crtc_clock;
 
@@ -1355,6 +1356,10 @@ static bool vlv_compute_drain_latency(struct drm_crtc *crtc,
 		return false;
 
 	entries = DIV_ROUND_UP(clock, 1000) * pixel_size;
+	if (IS_CHERRYVIEW(dev))
+		*prec_mult = (entries > 128) ? DRAIN_LATENCY_PRECISION_32 :
+					       DRAIN_LATENCY_PRECISION_16;
+	else
 		*prec_mult = (entries > 128) ? DRAIN_LATENCY_PRECISION_64 :
 					       DRAIN_LATENCY_PRECISION_32;
 	*drain_latency = (64 * (*prec_mult) * 4) / entries;
@@ -1375,15 +1380,18 @@ static bool vlv_compute_drain_latency(struct drm_crtc *crtc,
 
 static void vlv_update_drain_latency(struct drm_crtc *crtc)
 {
-	struct drm_i915_private *dev_priv = crtc->dev->dev_private;
+	struct drm_device *dev = crtc->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	int pixel_size;
 	int drain_latency;
 	enum pipe pipe = intel_crtc->pipe;
 	int plane_prec, prec_mult, plane_dl;
+	const int high_precision = IS_CHERRYVIEW(dev) ?
+		DRAIN_LATENCY_PRECISION_32 : DRAIN_LATENCY_PRECISION_64;
 
-	plane_dl = I915_READ(VLV_DDL(pipe)) & ~(DDL_PLANE_PRECISION_64 |
-		   DRAIN_LATENCY_MASK | DDL_CURSOR_PRECISION_64 |
+	plane_dl = I915_READ(VLV_DDL(pipe)) & ~(DDL_PLANE_PRECISION_HIGH |
+		   DRAIN_LATENCY_MASK | DDL_CURSOR_PRECISION_HIGH |
 		   (DRAIN_LATENCY_MASK << DDL_CURSOR_SHIFT));
 
 	if (!intel_crtc_active(crtc)) {
@@ -1394,9 +1402,9 @@ static void vlv_update_drain_latency(struct drm_crtc *crtc)
 	/* Primary plane Drain Latency */
 	pixel_size = crtc->primary->fb->bits_per_pixel / 8;	/* BPP */
 	if (vlv_compute_drain_latency(crtc, pixel_size, &prec_mult, &drain_latency)) {
-		plane_prec = (prec_mult == DRAIN_LATENCY_PRECISION_64) ?
-					   DDL_PLANE_PRECISION_64 :
-					   DDL_PLANE_PRECISION_32;
+		plane_prec = (prec_mult == high_precision) ?
+					   DDL_PLANE_PRECISION_HIGH :
+					   DDL_PLANE_PRECISION_LOW;
 		plane_dl |= plane_prec | drain_latency;
 	}
 
@@ -1408,9 +1416,9 @@ static void vlv_update_drain_latency(struct drm_crtc *crtc)
 	/* Program cursor DL only if it is enabled */
 	if (intel_crtc->cursor_base &&
 	    vlv_compute_drain_latency(crtc, pixel_size, &prec_mult, &drain_latency)) {
-		plane_prec = (prec_mult == DRAIN_LATENCY_PRECISION_64) ?
-					   DDL_CURSOR_PRECISION_64 :
-					   DDL_CURSOR_PRECISION_32;
+		plane_prec = (prec_mult == high_precision) ?
+					   DDL_CURSOR_PRECISION_HIGH :
+					   DDL_CURSOR_PRECISION_LOW;
 		plane_dl |= plane_prec | (drain_latency << DDL_CURSOR_SHIFT);
 	}
 
@@ -1578,15 +1586,17 @@ static void valleyview_update_sprite_wm(struct drm_plane *plane,
 	int plane_prec;
 	int sprite_dl;
 	int prec_mult;
+	const int high_precision = IS_CHERRYVIEW(dev) ?
+		DRAIN_LATENCY_PRECISION_32 : DRAIN_LATENCY_PRECISION_64;
 
-	sprite_dl = I915_READ(VLV_DDL(pipe)) & ~(DDL_SPRITE_PRECISION_64(sprite) |
+	sprite_dl = I915_READ(VLV_DDL(pipe)) & ~(DDL_SPRITE_PRECISION_HIGH(sprite) |
 		    (DRAIN_LATENCY_MASK << DDL_SPRITE_SHIFT(sprite)));
 
 	if (enabled && vlv_compute_drain_latency(crtc, pixel_size, &prec_mult,
 						 &drain_latency)) {
-		plane_prec = (prec_mult == DRAIN_LATENCY_PRECISION_64) ?
-					   DDL_SPRITE_PRECISION_64(sprite) :
-					   DDL_SPRITE_PRECISION_32(sprite);
+		plane_prec = (prec_mult == high_precision) ?
+					   DDL_SPRITE_PRECISION_HIGH(sprite) :
+					   DDL_SPRITE_PRECISION_LOW(sprite);
 		sprite_dl |= plane_prec |
 			     (drain_latency << DDL_SPRITE_SHIFT(sprite));
 	}