[Intel-gfx] [PATCH 5/5] drm/i915: Optimize VLV/CHV display FIFO updates

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Use I915_{READ,WRITE}_FW() for updating the DSPARB registers on
VLV/CHV. This is less expesive as we can grab the uncore.lock across
the entire sequence of reads and writes instead of each register
access grabbing it.

This also allows us to eliminate the dsparb lock entirely as the
uncore.lock now effectively protects the contents of the DSPARB
registers.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c |  1 -
 drivers/gpu/drm/i915/i915_drv.h |  3 ---
 drivers/gpu/drm/i915/intel_pm.c | 36 +++++++++++++++++++++---------------
 3 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index b1e9027a4f80..debb74a2b2a9 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -827,7 +827,6 @@ static int i915_driver_init_early(struct drm_i915_private *dev_priv,
 
 	spin_lock_init(&dev_priv->mm.object_stat_lock);
 	spin_lock_init(&dev_priv->mmio_flip_lock);
-	spin_lock_init(&dev_priv->wm.dsparb_lock);
 	mutex_init(&dev_priv->sb_lock);
 	mutex_init(&dev_priv->modeset_restore_lock);
 	mutex_init(&dev_priv->av_mutex);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 3002996ddbed..6af0b1d33cab 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2375,9 +2375,6 @@ struct drm_i915_private {
 	} sagv_status;
 
 	struct {
-		/* protects DSPARB registers on pre-g4x/vlv/chv */
-		spinlock_t dsparb_lock;
-
 		/*
 		 * Raw watermark latency values:
 		 * in 0.1us units for WM0,
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 99e09f63d4b3..24cdc13a416a 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -1358,13 +1358,19 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state,
 
 	trace_vlv_fifo_size(crtc, sprite0_start, sprite1_start, fifo_size);
 
-	spin_lock(&dev_priv->wm.dsparb_lock);
+	/*
+	 * uncore.lock serves a double purpose here. It allows us to
+	 * use the less expensive I915_{READ,WRITE}_FW() functions, and
+	 * it protects the DSPARB registers from getting clobbered by
+	 * parallel updates from multiple pipes.
+	 */
+	spin_lock(&dev_priv->uncore.lock);
 
 	switch (crtc->pipe) {
 		uint32_t dsparb, dsparb2, dsparb3;
 	case PIPE_A:
-		dsparb = I915_READ(DSPARB);
-		dsparb2 = I915_READ(DSPARB2);
+		dsparb = I915_READ_FW(DSPARB);
+		dsparb2 = I915_READ_FW(DSPARB2);
 
 		dsparb &= ~(VLV_FIFO(SPRITEA, 0xff) |
 			    VLV_FIFO(SPRITEB, 0xff));
@@ -1376,12 +1382,12 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state,
 		dsparb2 |= (VLV_FIFO(SPRITEA_HI, sprite0_start >> 8) |
 			   VLV_FIFO(SPRITEB_HI, sprite1_start >> 8));
 
-		I915_WRITE(DSPARB, dsparb);
-		I915_WRITE(DSPARB2, dsparb2);
+		I915_WRITE_FW(DSPARB, dsparb);
+		I915_WRITE_FW(DSPARB2, dsparb2);
 		break;
 	case PIPE_B:
-		dsparb = I915_READ(DSPARB);
-		dsparb2 = I915_READ(DSPARB2);
+		dsparb = I915_READ_FW(DSPARB);
+		dsparb2 = I915_READ_FW(DSPARB2);
 
 		dsparb &= ~(VLV_FIFO(SPRITEC, 0xff) |
 			    VLV_FIFO(SPRITED, 0xff));
@@ -1393,12 +1399,12 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state,
 		dsparb2 |= (VLV_FIFO(SPRITEC_HI, sprite0_start >> 8) |
 			   VLV_FIFO(SPRITED_HI, sprite1_start >> 8));
 
-		I915_WRITE(DSPARB, dsparb);
-		I915_WRITE(DSPARB2, dsparb2);
+		I915_WRITE_FW(DSPARB, dsparb);
+		I915_WRITE_FW(DSPARB2, dsparb2);
 		break;
 	case PIPE_C:
-		dsparb3 = I915_READ(DSPARB3);
-		dsparb2 = I915_READ(DSPARB2);
+		dsparb3 = I915_READ_FW(DSPARB3);
+		dsparb2 = I915_READ_FW(DSPARB2);
 
 		dsparb3 &= ~(VLV_FIFO(SPRITEE, 0xff) |
 			     VLV_FIFO(SPRITEF, 0xff));
@@ -1410,16 +1416,16 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state,
 		dsparb2 |= (VLV_FIFO(SPRITEE_HI, sprite0_start >> 8) |
 			   VLV_FIFO(SPRITEF_HI, sprite1_start >> 8));
 
-		I915_WRITE(DSPARB3, dsparb3);
-		I915_WRITE(DSPARB2, dsparb2);
+		I915_WRITE_FW(DSPARB3, dsparb3);
+		I915_WRITE_FW(DSPARB2, dsparb2);
 		break;
 	default:
 		break;
 	}
 
-	POSTING_READ(DSPARB);
+	POSTING_READ_FW(DSPARB);
 
-	spin_unlock(&dev_priv->wm.dsparb_lock);
+	spin_unlock(&dev_priv->uncore.lock);
 }
 
 #undef VLV_FIFO
-- 
2.10.2