drm/i915: Rework sdvo proxy i2c locking

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

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 3c9e00d4ba5a5bcb176a23ff12621368ba83f38c..6698826954e15d98d55bb2b1e35e7520527c4f00 100644 (file)
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -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

diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index e58a47db9a9de354ecce771d657e9fb340ef59c0..c14c05e8a5437b1417e4556670dfb566ced20c70 100644 (file)
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -451,23 +451,24 @@ static const char * const cmd_status_names[] = {
        "Scaling not supported"
 };
 
-static bool intel_sdvo_write_cmd(struct intel_sdvo *intel_sdvo, u8 cmd,
-                                const void *args, int args_len)
+static bool __intel_sdvo_write_cmd(struct intel_sdvo *intel_sdvo, u8 cmd,
+                                  const void *args, int args_len,
+                                  bool unlocked)
 {
        u8 *buf, status;
        struct i2c_msg *msgs;
        int i, ret = true;
 
-        /* Would be simpler to allocate both in one go ? */        
+       /* Would be simpler to allocate both in one go ? */
        buf = kzalloc(args_len * 2 + 2, GFP_KERNEL);
        if (!buf)
                return false;
 
        msgs = kcalloc(args_len + 3, sizeof(*msgs), GFP_KERNEL);
        if (!msgs) {
-               kfree(buf);
+               kfree(buf);
                return false;
-        }
+       }
 
        intel_sdvo_debug_write(intel_sdvo, cmd, args, args_len);
 
@@ -498,7 +499,10 @@ static bool intel_sdvo_write_cmd(struct intel_sdvo *intel_sdvo, u8 cmd,
        msgs[i+2].len = 1;
        msgs[i+2].buf = &status;
 
-       ret = i2c_transfer(intel_sdvo->i2c, msgs, i+3);
+       if (unlocked)
+               ret = i2c_transfer(intel_sdvo->i2c, msgs, i+3);
+       else
+               ret = __i2c_transfer(intel_sdvo->i2c, msgs, i+3);
        if (ret < 0) {
                DRM_DEBUG_KMS("I2c transfer returned %d\n", ret);
                ret = false;
@@ -516,6 +520,12 @@ out:
        return ret;
 }
 
+static bool intel_sdvo_write_cmd(struct intel_sdvo *intel_sdvo, u8 cmd,
+                                const void *args, int args_len)
+{
+       return __intel_sdvo_write_cmd(intel_sdvo, cmd, args, args_len, true);
+}
+
 static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo,
                                     void *response, int response_len)
 {
@@ -602,13 +612,13 @@ static int intel_sdvo_get_pixel_multiplier(const struct drm_display_mode *adjust
                return 4;
 }
 
-static bool intel_sdvo_set_control_bus_switch(struct intel_sdvo *intel_sdvo,
-                                             u8 ddc_bus)
+static bool __intel_sdvo_set_control_bus_switch(struct intel_sdvo *intel_sdvo,
+                                               u8 ddc_bus)
 {
        /* This must be the immediately preceding write before the i2c xfer */
-       return intel_sdvo_write_cmd(intel_sdvo,
-                                   SDVO_CMD_SET_CONTROL_BUS_SWITCH,
-                                   &ddc_bus, 1);
+       return __intel_sdvo_write_cmd(intel_sdvo,
+                                     SDVO_CMD_SET_CONTROL_BUS_SWITCH,
+                                     &ddc_bus, 1, false);
 }
 
 static bool intel_sdvo_set_value(struct intel_sdvo *intel_sdvo, u8 cmd, const void *data, int len)
@@ -2926,7 +2936,7 @@ static int intel_sdvo_ddc_proxy_xfer(struct i2c_adapter *adapter,
 {
        struct intel_sdvo *sdvo = adapter->algo_data;
 
-       if (!intel_sdvo_set_control_bus_switch(sdvo, sdvo->ddc_bus))
+       if (!__intel_sdvo_set_control_bus_switch(sdvo, sdvo->ddc_bus))
                return -EIO;
 
        return sdvo->i2c->algo->master_xfer(sdvo->i2c, msgs, num);
@@ -2943,6 +2953,33 @@ static const struct i2c_algorithm intel_sdvo_ddc_proxy = {
        .functionality  = intel_sdvo_ddc_proxy_func
 };
 
+static void proxy_lock_bus(struct i2c_adapter *adapter,
+                          unsigned int flags)
+{
+       struct intel_sdvo *sdvo = adapter->algo_data;
+       sdvo->i2c->lock_ops->lock_bus(sdvo->i2c, flags);
+}
+
+static int proxy_trylock_bus(struct i2c_adapter *adapter,
+                            unsigned int flags)
+{
+       struct intel_sdvo *sdvo = adapter->algo_data;
+       return sdvo->i2c->lock_ops->trylock_bus(sdvo->i2c, flags);
+}
+
+static void proxy_unlock_bus(struct i2c_adapter *adapter,
+                            unsigned int flags)
+{
+       struct intel_sdvo *sdvo = adapter->algo_data;
+       sdvo->i2c->lock_ops->unlock_bus(sdvo->i2c, flags);
+}
+
+const struct i2c_lock_operations proxy_lock_ops = {
+       .lock_bus =    proxy_lock_bus,
+       .trylock_bus = proxy_trylock_bus,
+       .unlock_bus =  proxy_unlock_bus,
+};
+
 static bool
 intel_sdvo_init_ddc_proxy(struct intel_sdvo *sdvo,
                          struct drm_i915_private *dev_priv)
@@ -2955,6 +2992,7 @@ intel_sdvo_init_ddc_proxy(struct intel_sdvo *sdvo,
        sdvo->ddc.dev.parent = &pdev->dev;
        sdvo->ddc.algo_data = sdvo;
        sdvo->ddc.algo = &intel_sdvo_ddc_proxy;
+       sdvo->ddc.lock_ops = &proxy_lock_ops;
 
        return i2c_add_adapter(&sdvo->ddc) == 0;
 }