[PATCH v4 1/9] i2c: atr: Fix lockdep for nested ATRs

Cosmin Tanislav
2025-04-28T10:25:26Z

From: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>

When we have an ATR, and another ATR as a subdevice of the first ATR,
we get lockdep warnings for the i2c_atr.lock and
i2c_atr_chan.orig_addrs_lock. This is because lockdep uses a static key
for the locks, and doesn't see the locks of the separate ATR instances
as separate.

Fix this by generating a dynamic lock key per lock instance.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
---
drivers/i2c/i2c-atr.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
index 1aeaecacc26c..a79ca87e8bbd 100644
--- a/drivers/i2c/i2c-atr.c
+++ b/drivers/i2c/i2c-atr.c
@@ -68,11 +68,13 @@ struct i2c_atr_alias_pool {
* @atr: The parent I2C ATR
* @chan_id: The ID of this channel
* @alias_pairs_lock: Mutex protecting @alias_pairs
+ * @alias_pairs_lock_key: Lock key for @alias_pairs_lock
* @alias_pairs: List of @struct i2c_atr_alias_pair containing the
* assigned aliases
* @alias_pool: Pool of available client aliases
*
* @orig_addrs_lock: Mutex protecting @orig_addrs
+ * @orig_addrs_lock_key: Lock key for @orig_addrs_lock
* @orig_addrs: Buffer used to store the original addresses during transmit
* @orig_addrs_size: Size of @orig_addrs
*/
@@ -83,11 +85,13 @@ struct i2c_atr_chan {

/* Lock alias_pairs during attach/detach */
struct mutex alias_pairs_lock;
+ struct lock_class_key alias_pairs_lock_key;
struct list_head alias_pairs;
struct i2c_atr_alias_pool *alias_pool;

/* Lock orig_addrs during xfer */
struct mutex orig_addrs_lock;
+ struct lock_class_key orig_addrs_lock_key;
u16 *orig_addrs;
unsigned int orig_addrs_size;
};
@@ -100,6 +104,7 @@ struct i2c_atr_chan {
* @priv: Private driver data, set with i2c_atr_set_driver_data()
* @algo: The &struct i2c_algorithm for adapters
* @lock: Lock for the I2C bus segment (see &struct i2c_lock_operations)
+ * @lock_key: Lock key for @lock
* @max_adapters: Maximum number of adapters this I2C ATR can have
* @alias_pool: Optional common pool of available client aliases
* @i2c_nb: Notifier for remote client add & del events
@@ -115,6 +120,7 @@ struct i2c_atr {
struct i2c_algorithm algo;
/* lock for the I2C bus segment (see struct i2c_lock_operations) */
struct mutex lock;
+ struct lock_class_key lock_key;
int max_adapters;

struct i2c_atr_alias_pool *alias_pool;
@@ -683,7 +689,8 @@ struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
if (!atr)
return ERR_PTR(-ENOMEM);

- mutex_init(&atr->lock);
+ lockdep_register_key(&atr->lock_key);
+ mutex_init_with_key(&atr->lock, &atr->lock_key);

atr->parent = parent;
atr->dev = dev;
@@ -711,6 +718,7 @@ struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
i2c_atr_free_alias_pool(atr->alias_pool);
err_destroy_mutex:
mutex_destroy(&atr->lock);
+ lockdep_unregister_key(&atr->lock_key);
kfree(atr);

return ERR_PTR(ret);
@@ -727,6 +735,7 @@ void i2c_atr_delete(struct i2c_atr *atr)
bus_unregister_notifier(&i2c_bus_type, &atr->i2c_nb);
i2c_atr_free_alias_pool(atr->alias_pool);
mutex_destroy(&atr->lock);
+ lockdep_unregister_key(&atr->lock_key);
kfree(atr);
}
EXPORT_SYMBOL_NS_GPL(i2c_atr_delete, "I2C_ATR");
@@ -761,8 +770,10 @@ int i2c_atr_add_adapter(struct i2c_atr *atr, struct i2c_atr_adap_desc *desc)
chan->atr = atr;
chan->chan_id = chan_id;
INIT_LIST_HEAD(&chan->alias_pairs);
- mutex_init(&chan->alias_pairs_lock);
- mutex_init(&chan->orig_addrs_lock);
+ lockdep_register_key(&chan->alias_pairs_lock_key);
+ lockdep_register_key(&chan->orig_addrs_lock_key);
+ mutex_init_with_key(&chan->alias_pairs_lock, &chan->alias_pairs_lock_key);
+ mutex_init_with_key(&chan->orig_addrs_lock, &chan->orig_addrs_lock_key);

snprintf(chan->adap.name, sizeof(chan->adap.name), "i2c-%d-atr-%d",
i2c_adapter_id(parent), chan_id);
@@ -839,6 +850,8 @@ int i2c_atr_add_adapter(struct i2c_atr *atr, struct i2c_atr_adap_desc *desc)
fwnode_handle_put(dev_fwnode(&chan->adap.dev));
mutex_destroy(&chan->orig_addrs_lock);
mutex_destroy(&chan->alias_pairs_lock);
+ lockdep_unregister_key(&chan->orig_addrs_lock_key);
+ lockdep_unregister_key(&chan->alias_pairs_lock_key);
kfree(chan);
return ret;
}
@@ -876,6 +889,8 @@ void i2c_atr_del_adapter(struct i2c_atr *atr, u32 chan_id)
fwnode_handle_put(fwnode);
mutex_destroy(&chan->orig_addrs_lock);
mutex_destroy(&chan->alias_pairs_lock);
+ lockdep_unregister_key(&chan->orig_addrs_lock_key);
+ lockdep_unregister_key(&chan->alias_pairs_lock_key);
kfree(chan->orig_addrs);
kfree(chan);
}
--
2.49.0