lkml.org 
[lkml]   [2012]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] [PATCH] drm/i915: Fix race condition in accessing GMBUS
Date
GMBUS has several ports and each has it's own corresponding
I2C adpater. When multiple I2C adapters call gmbus_xfer() at
the same time there is a race condition in using the underlying
GMBUS controller. Fixing this by adding a mutex lock when calling
gmbus_xfer().

Signed-off-by: Yufeng Shen <miletus@chromium.org>
---
drivers/gpu/drm/i915/i915_drv.h | 2 ++
drivers/gpu/drm/i915/intel_i2c.c | 23 +++++++++++++++++------
2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 559fb6f..4ed9fd9 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -722,6 +722,8 @@ typedef struct drm_i915_private {
u8 corr;
spinlock_t *mchdev_lock;

+ struct mutex gmbus_mutex;
+
enum no_fbc_reason no_fbc_reason;

struct drm_mm_node *compressed_fb;
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index d98cee6..42569b1 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -232,11 +232,15 @@ 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;

@@ -320,7 +324,8 @@ done:
* 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",
@@ -330,9 +335,13 @@ timeout:
/* 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;
+ ret = -ENOMEM;
+ else
+ ret = intel_i2c_quirk_xfer(dev_priv, bus->force_bit, msgs, num);

- return 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)
@@ -379,6 +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];

--
1.7.3.4


\
 
 \ /
  Last update: 2012-02-10 18:53    [W:0.097 / U:40.796 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site