Lockdep validator complains recursive locking and deadlock when two
different regmap instances are called in a nested order, as regmap
groups locks by default. That happens easily for example when both
I2C client and I2C adapter are using regmap. As a solution, add
configuration option to pass custom lock class key for lockdep
validator.
Here is example schema, where nested regmap calls are issued, when
more than 1 block uses regmap.
__________ ___________ ___________
| USB IF | | demod | | tuner |
|----------| |-----------| |-----------|
| |--I2C--|-----/ ----|--I2C--| |
|I2C master| | I2C mux | | I2C slave |
|__________| |___________| |___________|
Cc: Lars-Peter Clausen <lars@xxxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Antti Palosaari <crope@xxxxxx>
---
drivers/base/regmap/regmap.c | 3 +++
include/linux/regmap.h | 5 +++++
2 files changed, 8 insertions(+)
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index d2f8a81..56064d3 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -559,6 +559,9 @@ struct regmap *regmap_init(struct device *dev,
mutex_init(&map->mutex);
map->lock = regmap_lock_mutex;
map->unlock = regmap_unlock_mutex;
+ if (config->lockdep_lock_class_key)
+ lockdep_set_class(&map->mutex,
+ config->lockdep_lock_class_key);
}
map->lock_arg = map;
}
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index c5ed83f..f930370 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -134,6 +134,10 @@ typedef void (*regmap_unlock)(void *);
* @lock_arg: this field is passed as the only argument of lock/unlock
* functions (ignored in case regular lock/unlock functions
* are not overridden).
+ * @lock_class_key: Custom lock class key for lockdep validator. Use that when
+ * regmap in question is used for bus master IO in order to avoid
+ * false lockdep nested locking warning. Valid only when regmap
+ * default mutex locking is used.
* @reg_read: Optional callback that if filled will be used to perform
* all the reads from the registers. Should only be provided for
* devices whose read operation cannot be represented as a simple
@@ -197,6 +201,7 @@ struct regmap_config {
regmap_lock lock;
regmap_unlock unlock;
void *lock_arg;
+ struct lock_class_key *lockdep_lock_class_key;
int (*reg_read)(void *context, unsigned int reg, unsigned int *val);
int (*reg_write)(void *context, unsigned int reg, unsigned int val);
--
http://palosaari.fi/
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
