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drm/i915: Fix race condition in accessing GMBUS 

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().

v2: Moved gmbus_mutex below intel_gmbus and added comments.
Rebased to drm-intel-next-queued.

Signed-off-by: Yufeng Shen <miletus@chromium.org>
[danvet: Shortened the gmbus_mutex comment a bit and add the patch
revision comment to the commit message.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Yufeng Shen 2012-02-13 17:36:54 -05:00 committed by Daniel Vetter
parent b1d7e4b41f
commit 8a8ed1f514
2 changed files with 21 additions and 7 deletions
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4
drivers/gpu/drm/i915/i915_drv.h
View File

@ -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;

24
drivers/gpu/drm/i915/intel_i2c.c
View File

@ -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 @@ 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",
@ -331,9 +336,12 @@ 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;
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];