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

["Boyer, Wayne" <wayne.boyer@intel.com>]

Tested-by: Wayne Boyer <wayne.boyer@intel.com>

Before this patch I was getting pipe underrun errors on pipe A and pipe C
when
running various workloads.  Shortly after the errors, the screens would go
black
and could not be recovered without rebooting.

With this patch I don't get the underrun errors and the machine has been
stable.

On 10/17/14, 8:05 AM, "Vivi, Rodrigo" <rodrigo.vivi@intel.com> wrote:

>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>
>---
> drivers/gpu/drm/i915/i915_reg.h | 13 +++++++------
> drivers/gpu/drm/i915/intel_pm.c | 40
>+++++++++++++++++++++++++---------------
> 2 files changed, 32 insertions(+), 21 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/i915_reg.h
>b/drivers/gpu/drm/i915/i915_reg.h
>index 6db369a..dcd5650 100644
>--- a/drivers/gpu/drm/i915/i915_reg.h
>+++ b/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
> 
>diff --git a/drivers/gpu/drm/i915/intel_pm.c
>b/drivers/gpu/drm/i915/intel_pm.c
>index daa99e7..50c3512 100644
>--- a/drivers/gpu/drm/i915/intel_pm.c
>+++ b/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;
> 
>@@ -1355,8 +1356,12 @@ static bool vlv_compute_drain_latency(struct
>drm_crtc *crtc,
> 		return false;
> 
> 	entries = DIV_ROUND_UP(clock, 1000) * pixel_size;
>-	*prec_mult = (entries > 128) ? DRAIN_LATENCY_PRECISION_64 :
>-				       DRAIN_LATENCY_PRECISION_32;
>+	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;
> 
> 	if (*drain_latency > DRAIN_LATENCY_MASK)
>@@ -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;
>+	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;
>+	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));
> 	}
>-- 
>1.9.3
>