From 8a8ed1f5143b3df312e436ab15290e4a7ca6a559 Mon Sep 17 00:00:00 2001 From: Yufeng Shen Date: Mon, 13 Feb 2012 17:36:54 -0500 Subject: [PATCH] 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 [danvet: Shortened the gmbus_mutex comment a bit and add the patch revision comment to the commit message.] Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_drv.h | 4 ++++ drivers/gpu/drm/i915/intel_i2c.c | 24 +++++++++++++++++------- 2 files changed, 21 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index caec1fd..8e3eb5e 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/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/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index d30cccc..fc75d71 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/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 @@ 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]; -- 2.7.4