[PATCH 11/11 v3] drm/i915/intel_i2c: reuse GMBUS2 value read in polling loop

[Daniel Kurtz]

Save the GMBUS2 value read while polling for state changes, and then
reuse this value when determining for which reason the loops were exited.
This is a small optimization which saves a couple of bus accesses for
memory mapped IO registers.

Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_i2c.c |   17 +++++++++--------
 1 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 9619bde..7674c89 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -214,6 +214,7 @@ gmbus_xfer(struct i2c_adapter *adapter,
 	struct drm_i915_private *dev_priv = bus->dev_priv;
 	int i, reg_offset;
 	int ret = 0;
+	u32 gmbus2 = 0;
 
 	mutex_lock(&dev_priv->gmbus_mutex);
 
@@ -268,12 +269,12 @@ gmbus_xfer(struct i2c_adapter *adapter,
 			do {
 				u32 val, loop = 0;
 
-				if (wait_for(I915_READ(GMBUS2 + reg_offset) &
+				if (wait_for((gmbus2 = I915_READ(GMBUS2 +
+								 reg_offset)) &
 					     (GMBUS_SATOER | GMBUS_HW_RDY),
 					     50))
 					goto timeout;
-				if (I915_READ(GMBUS2 + reg_offset) &
-				    GMBUS_SATOER)
+				if (gmbus2 & GMBUS_SATOER)
 					goto clear_err;
 
 				val = I915_READ(GMBUS3 + reg_offset);
@@ -308,21 +309,21 @@ gmbus_xfer(struct i2c_adapter *adapter,
 				I915_WRITE(GMBUS3 + reg_offset, val);
 				POSTING_READ(GMBUS2 + reg_offset);
 
-				if (wait_for(I915_READ(GMBUS2 + reg_offset) &
+				if (wait_for((gmbus2 = I915_READ(GMBUS2 +
+								 reg_offset)) &
 					     (GMBUS_SATOER | GMBUS_HW_RDY),
 					     50))
 					goto timeout;
-				if (I915_READ(GMBUS2 + reg_offset) &
-				    GMBUS_SATOER)
+				if (gmbus2 & GMBUS_SATOER)
 					goto clear_err;
 			}
 		}
 
-		if (wait_for(I915_READ(GMBUS2 + reg_offset) &
+		if (wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
 			     (GMBUS_SATOER | GMBUS_HW_WAIT_PHASE),
 			     50))
 			goto timeout;
-		if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER)
+		if (gmbus2 & GMBUS_SATOER)
 			goto clear_err;
 	}
 
-- 
1.7.7.3