From 894c957383bef0cd48b2528fe09a1647bd23acc2 Mon Sep 17 00:00:00 2001
From: Yufeng Shen <miletus@chromium.org>
Date: Mon, 13 Feb 2012 17:36:54 -0500
Subject: [PATCH] --- yaml --- r: 293599 b: refs/heads/master c:
 8a8ed1f5143b3df312e436ab15290e4a7ca6a559 h: refs/heads/master i:   293597:
 657468e7caab58b58f73da16296c87003bdfae5b   293595:
 317b765fee804a4a688307a26a18f9e85bbc3911   293591:
 e85339a7125cc2bd8b23ae7d8a5f99096fb7e750   293583:
 96ec1c51125c98991467b252030f6c736b561c3d   293567:
 26128c43cc1c4302980a1f6db5eaf6fd527e27d6 v: v3

---
 [refs]                                 |  2 +-
 trunk/drivers/gpu/drm/i915/i915_drv.h  |  4 ++++
 trunk/drivers/gpu/drm/i915/intel_i2c.c | 24 +++++++++++++++++-------
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index 6eb2e4624fc4..aca780eea0a1 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b1d7e4b41fd0f72ea8149056778db5d737739305
+refs/heads/master: 8a8ed1f5143b3df312e436ab15290e4a7ca6a559
diff --git a/trunk/drivers/gpu/drm/i915/i915_drv.h b/trunk/drivers/gpu/drm/i915/i915_drv.h
index caec1fdb7dda..8e3eb5e282a1 100644
--- a/trunk/drivers/gpu/drm/i915/i915_drv.h
+++ b/trunk/drivers/gpu/drm/i915/i915_drv.h
@@ -313,6 +313,10 @@ typedef struct drm_i915_private {
 		u32 reg0;
 	} *gmbus;
 
+	/** gmbus_mutex protects against concurrent usage of the single hw gmbus
+	 * controller on different i2c buses. */
+	struct mutex gmbus_mutex;
+
 	struct pci_dev *bridge_dev;
 	struct intel_ring_buffer ring[I915_NUM_RINGS];
 	uint32_t next_seqno;
diff --git a/trunk/drivers/gpu/drm/i915/intel_i2c.c b/trunk/drivers/gpu/drm/i915/intel_i2c.c
index d30ccccb9d73..fc75d71de53b 100644
--- a/trunk/drivers/gpu/drm/i915/intel_i2c.c
+++ b/trunk/drivers/gpu/drm/i915/intel_i2c.c
@@ -233,11 +233,15 @@ gmbus_xfer(struct i2c_adapter *adapter,
 					       struct intel_gmbus,
 					       adapter);
 	struct drm_i915_private *dev_priv = adapter->algo_data;
-	int i, reg_offset;
+	int i, reg_offset, ret;
 
-	if (bus->force_bit)
-		return intel_i2c_quirk_xfer(dev_priv,
+	mutex_lock(&dev_priv->gmbus_mutex);
+
+	if (bus->force_bit) {
+		ret = intel_i2c_quirk_xfer(dev_priv,
 					    bus->force_bit, msgs, num);
+		goto out;
+	}
 
 	reg_offset = HAS_PCH_SPLIT(dev_priv->dev) ? PCH_GMBUS0 - GMBUS0 : 0;
 
@@ -321,7 +325,8 @@ gmbus_xfer(struct i2c_adapter *adapter,
 	 * start of the next xfer, till then let it sleep.
 	 */
 	I915_WRITE(GMBUS0 + reg_offset, 0);
-	return i;
+	ret = i;
+	goto out;
 
 timeout:
 	DRM_INFO("GMBUS timed out, falling back to bit banging on pin %d [%s]\n",
@@ -331,9 +336,12 @@ gmbus_xfer(struct i2c_adapter *adapter,
 	/* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */
 	bus->force_bit = intel_gpio_create(dev_priv, bus->reg0 & 0xff);
 	if (!bus->force_bit)
-		return -ENOMEM;
-
-	return intel_i2c_quirk_xfer(dev_priv, bus->force_bit, msgs, num);
+		ret = -ENOMEM;
+	else
+		ret = intel_i2c_quirk_xfer(dev_priv, bus->force_bit, msgs, num);
+out:
+	mutex_unlock(&dev_priv->gmbus_mutex);
+	return ret;
 }
 
 static u32 gmbus_func(struct i2c_adapter *adapter)
@@ -380,6 +388,8 @@ int intel_setup_gmbus(struct drm_device *dev)
 	if (dev_priv->gmbus == NULL)
 		return -ENOMEM;
 
+	mutex_init(&dev_priv->gmbus_mutex);
+
 	for (i = 0; i < GMBUS_NUM_PORTS; i++) {
 		struct intel_gmbus *bus = &dev_priv->gmbus[i];