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drm/i915: Rework sdvo proxy i2c locking

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lockdep complaints about a locking recursion for the i2c bus lock
because both the sdvo ddc proxy bus and the gmbus nested within use
the same locking class. It's not really a deadlock since we never nest
the other way round, but it's annoying.

Fix it by pulling the gmbus locking into the i2c lock_ops for both
i2c_adapater and making sure that the ddc_proxy_xfer function is
entirely lockless.

Re-layouting the extracted function resulted in some whitespace
cleanups, I figured we might as well keep them.

v2: Review from Chris:
- s/locked/unlocked/ since I got the naming backwards
- Use the vfuncs of the proxied adatper instead of re-rolling copies.
  That's more consistent with the other proxying we're doing.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170726132647.31833-1-daniel.vetter@ffwll.ch
This commit is contained in:
Daniel Vetter
2017-07-26 15:26:47 +02:00
parent 8fb6a5df46
commit a85066840d
2 changed files with 84 additions and 14 deletions
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36
drivers/gpu/drm/i915/intel_i2c.c
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@@ -592,7 +592,6 @@ gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
int ret;
intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
mutex_lock(&dev_priv->gmbus_mutex);
if (bus->force_bit) {
ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
@@ -604,7 +603,6 @@ gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
bus->force_bit |= GMBUS_FORCE_BIT_RETRY;
}
mutex_unlock(&dev_priv->gmbus_mutex);
intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);
return ret;
@@ -624,6 +622,39 @@ static const struct i2c_algorithm gmbus_algorithm = {
.functionality = gmbus_func
};
static void gmbus_lock_bus(struct i2c_adapter *adapter,
unsigned int flags)
{
struct intel_gmbus *bus = to_intel_gmbus(adapter);
struct drm_i915_private *dev_priv = bus->dev_priv;
mutex_lock(&dev_priv->gmbus_mutex);
}
static int gmbus_trylock_bus(struct i2c_adapter *adapter,
unsigned int flags)
{
struct intel_gmbus *bus = to_intel_gmbus(adapter);
struct drm_i915_private *dev_priv = bus->dev_priv;
return mutex_trylock(&dev_priv->gmbus_mutex);
}
static void gmbus_unlock_bus(struct i2c_adapter *adapter,
unsigned int flags)
{
struct intel_gmbus *bus = to_intel_gmbus(adapter);
struct drm_i915_private *dev_priv = bus->dev_priv;
mutex_unlock(&dev_priv->gmbus_mutex);
}
const struct i2c_lock_operations gmbus_lock_ops = {
.lock_bus = gmbus_lock_bus,
.trylock_bus = gmbus_trylock_bus,
.unlock_bus = gmbus_unlock_bus,
};
/**
* intel_gmbus_setup - instantiate all Intel i2c GMBuses
* @dev_priv: i915 device private
@@ -665,6 +696,7 @@ int intel_setup_gmbus(struct drm_i915_private *dev_priv)
bus->dev_priv = dev_priv;
bus->adapter.algo = &gmbus_algorithm;
bus->adapter.lock_ops = &gmbus_lock_ops;
/*
* We wish to retry with bit banging