[PATCH v3 3/4] drm/i915: Skip CURBASE write when nothing changed

[ville.syrjala@linux.intel.com]

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

Only write CURBASE when something about the cursor changed. Also
eliminate the unnecessary posting read after writing CURCNTR.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 82c0ad1..60c1aa4 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8322,16 +8322,18 @@ static void i9xx_update_cursor(struct drm_crtc *crtc, u32 base)
 			cntl |= CURSOR_PIPE_CSC_ENABLE;
 	}
 
-	if (intel_crtc->cursor_cntl != cntl) {
+	if (intel_crtc->cursor_cntl != cntl)
 		I915_WRITE(CURCNTR(pipe), cntl);
-		POSTING_READ(CURCNTR(pipe));
-		intel_crtc->cursor_cntl = cntl;
-	}
+
+	if (intel_crtc->cursor_cntl == cntl &&
+	    intel_crtc->cursor_base == base)
+		return;
 
 	/* and commit changes on next vblank */
 	I915_WRITE(CURBASE(pipe), base);
 	POSTING_READ(CURBASE(pipe));
 
+	intel_crtc->cursor_cntl = cntl;
 	intel_crtc->cursor_base = base;
 }
 
-- 
1.8.5.5

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