[Intel-gfx] [PATCH 3/6] drm/i915: Optimize the VLV Punit wait a bit

[ville.syrjala at linux.intel.com]

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

Don't do needless udelay() calls if the Punit already completed
the frequency change.

Also double check things after the timeout to make sure the timeout
wasn't just caused by some scheduling delays.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 6dbcad7..6b98d45 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3078,14 +3078,20 @@ static void vlv_update_rps_cur_delay(struct drm_i915_private *dev_priv)
 
 	WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));
 
-	do {
-		pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
+	pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
+
+	while (pval & 1) {
 		if (time_after(jiffies, timeout)) {
-			DRM_DEBUG_DRIVER("timed out waiting for Punit\n");
+			pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
 			break;
 		}
+
 		udelay(10);
-	} while (pval & 1);
+		pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
+	}
+
+	if (pval & 1)
+		DRM_DEBUG_DRIVER("timed out waiting for Punit\n");
 
 	pval >>= 8;
 
-- 
1.8.1.5