[Intel-gfx] [PATCH] drm/i915: Rework sdvo proxy i2c locking
Daniel Vetter
daniel.vetter at ffwll.ch
Wed Jul 26 13:26:47 UTC 2017
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 at chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
drivers/gpu/drm/i915/intel_i2c.c | 36 +++++++++++++++++++++--
drivers/gpu/drm/i915/intel_sdvo.c | 62 +++++++++++++++++++++++++++++++--------
2 files changed, 84 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 3c9e00d4ba5a..6698826954e1 100644
--- 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 bea8152ae859..f09221dcd4c0 100644
--- 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 @@ static bool intel_sdvo_write_cmd(struct intel_sdvo *intel_sdvo, u8 cmd,
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)
@@ -2924,7 +2934,7 @@ 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);
@@ -2941,6 +2951,33 @@ 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)
@@ -2953,6 +2990,7 @@ 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;
}
--
2.13.3
More information about the Intel-gfx
mailing list