linux-kernel - [PATCH 13/13 v4] drm/i915/intel_i2c: reuse GMBUS2 value read in polling loop

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Message-Id: <1332873382-29373-14-git-send-email-djkurtz@chromium.org>
Date:	Wed, 28 Mar 2012 02:36:22 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	Daniel Vetter <daniel@...ll.ch>, Keith Packard <keithp@...thp.com>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:	Benson Leung <bleung@...omium.org>,
	Yufeng Shen <miletus@...omium.org>,
	Daniel Kurtz <djkurtz@...omium.org>
Subject: [PATCH 13/13 v4] drm/i915/intel_i2c: reuse GMBUS2 value read in polling loop

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.

To avoid "assigning in if clause" checkpatch errors", use a ret variable
to store the wait_for macro return value.

Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
---
 drivers/gpu/drm/i915/intel_i2c.c |   32 ++++++++++++++++++++------------
 1 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index c71f3dc..174fc71 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -210,6 +210,7 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
 	int reg_offset = dev_priv->gpio_mmio_base;
 	u16 len = msg->len;
 	u8 *buf = msg->buf;
+	u32 gmbus2;
 
 	I915_WRITE(GMBUS1 + reg_offset,
 		   gmbus1 |
@@ -219,13 +220,15 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
 		   GMBUS_SLAVE_READ | GMBUS_SW_RDY);
 	POSTING_READ(GMBUS2 + reg_offset);
 	do {
+		int ret;
 		u32 val, loop = 0;
 
-		if (wait_for(I915_READ(GMBUS2 + reg_offset) &
-			     (GMBUS_SATOER | GMBUS_HW_RDY),
-			     50))
+		ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
+			       (GMBUS_SATOER | GMBUS_HW_RDY),
+			       50);
+		if (ret)
 			return -ETIMEDOUT;
-		if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER)
+		if (gmbus2 & GMBUS_SATOER)
 			return -ENXIO;
 
 		val = I915_READ(GMBUS3 + reg_offset);
@@ -245,6 +248,7 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)
 	u16 len = msg->len;
 	u8 *buf = msg->buf;
 	u32 val, loop;
+	u32 gmbus2;
 
 	val = loop = 0;
 	while (len && loop < 4) {
@@ -260,6 +264,7 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)
 		   GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
 	POSTING_READ(GMBUS2 + reg_offset);
 	while (len) {
+		int ret;
 		val = loop = 0;
 		do {
 			val |= *buf++ << (8 * loop);
@@ -268,11 +273,12 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)
 		I915_WRITE(GMBUS3 + reg_offset, val);
 		POSTING_READ(GMBUS2 + reg_offset);
 
-		if (wait_for(I915_READ(GMBUS2 + reg_offset) &
-			     (GMBUS_SATOER | GMBUS_HW_RDY),
-			     50))
+		ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
+			       (GMBUS_SATOER | GMBUS_HW_RDY),
+			       50);
+		if (ret)
 			return -ETIMEDOUT;
-		if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER)
+		if (gmbus2 & GMBUS_SATOER)
 			return -ENXIO;
 	}
 	return 0;
@@ -289,6 +295,7 @@ 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);
 
@@ -338,11 +345,12 @@ gmbus_xfer(struct i2c_adapter *adapter,
 		if (ret == -ENXIO)
 			goto clear_err;
 
-		if (wait_for(I915_READ(GMBUS2 + reg_offset) &
-			     (GMBUS_SATOER | GMBUS_HW_WAIT_PHASE),
-			     50))
+		ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
+			       (GMBUS_SATOER | GMBUS_HW_WAIT_PHASE),
+			       50);
+		if (ret)
 			goto timeout;
-		if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER)
+		if (gmbus2 & GMBUS_SATOER)
 			goto clear_err;
 	}
 
-- 
1.7.7.3

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