[PATCH] PM: clk: Fix false-positive recursive PM clock mutex locking

[PATCH] PM: clk: Fix false-positive recursive PM clock mutex locking

[Daniel J Blueman]

pm_clk_suspend() and pm_clk_resume() hold psd->clock_mutex across
clk_prepare() and clk_unprepare() for sleeping clocks, with every instance
sharing one lockdep class. If a PM clock is provided by a device that also
uses PM clocks, clk_prepare() resumes the provider, which takes its own
clock mutex, triggering a lockdep report.

This shows up on the Qualcomm X1 with the LPASS WSA/RX/TX macros and the
varargs macro providing the "fsgen" clock:

  WARNING: possible recursive locking detected
  ...
   pm_clk_resume
   va_macro_runtime_resume [snd_soc_lpass_va_macro]
   ...
   clk_prepare
   pm_clk_resume
   wsa_macro_runtime_resume [snd_soc_lpass_wsa_macro]

Lock ordering is always consumer -> provider, so this is false-positive,
resulting in lockdep being turned off.

Fix this by giving each pm_clk_create()/devm_pm_clk_create() call site its
own lock class.

Scenario analysis and patch development was assisted by Claude Opus 5.5
under my instruction; detection and validation was performed on my Lenovo
Slim 7x with a X1E80100.

Fixes: eb667d0fbdd3 ("ASoC: codecs: lpass-va-macro: Switch to PM clock framework for runtime PM")
Signed-off-by: Daniel J Blueman <daniel@quora.org>
---
 drivers/base/power/clock_ops.c | 23 ++++++++++++++++-------
 include/linux/pm_clock.h       | 19 +++++++++++++++++--
 2 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
index 3b8ba27802a8..94f2aa090ce1 100644
--- a/drivers/base/power/clock_ops.c
+++ b/drivers/base/power/clock_ops.c
@@ -398,17 +398,26 @@ void pm_clk_init(struct device *dev)
 EXPORT_SYMBOL_GPL(pm_clk_init);
 
 /**
- * pm_clk_create - Create and initialize a device's list of PM clocks.
+ * __pm_clk_create - Create and initialize a device's list of PM clocks.
  * @dev: Device to create and initialize the list of PM clocks for.
+ * @key: Lockdep class key for the clock mutex.
  *
  * Allocate a struct pm_subsys_data object, initialize its lock and clock_list
  * members and make the @dev's power.subsys_data field point to it.
  */
-int pm_clk_create(struct device *dev)
+int __pm_clk_create(struct device *dev, struct lock_class_key *key)
 {
-	return dev_pm_get_subsys_data(dev);
+	int ret;
+
+	ret = dev_pm_get_subsys_data(dev);
+	if (ret)
+		return ret;
+
+	lockdep_set_class_and_name(&dev_to_psd(dev)->clock_mutex, key,
+				   "&psd->clock_mutex");
+	return 0;
 }
-EXPORT_SYMBOL_GPL(pm_clk_create);
+EXPORT_SYMBOL_GPL(__pm_clk_create);
 
 /**
  * pm_clk_destroy - Destroy a device's list of power management clocks.
@@ -451,17 +460,17 @@ static void pm_clk_destroy_action(void *data)
 	pm_clk_destroy(data);
 }
 
-int devm_pm_clk_create(struct device *dev)
+int __devm_pm_clk_create(struct device *dev, struct lock_class_key *key)
 {
 	int ret;
 
-	ret = pm_clk_create(dev);
+	ret = __pm_clk_create(dev, key);
 	if (ret)
 		return ret;
 
 	return devm_add_action_or_reset(dev, pm_clk_destroy_action, dev);
 }
-EXPORT_SYMBOL_GPL(devm_pm_clk_create);
+EXPORT_SYMBOL_GPL(__devm_pm_clk_create);
 
 /**
  * pm_clk_suspend - Disable clocks in a device's PM clock list.
diff --git a/include/linux/pm_clock.h b/include/linux/pm_clock.h
index c3b46fa358d3..d54681547f58 100644
--- a/include/linux/pm_clock.h
+++ b/include/linux/pm_clock.h
@@ -37,7 +37,7 @@ static inline bool pm_clk_no_clocks(struct device *dev)
 }
 
 extern void pm_clk_init(struct device *dev);
-extern int pm_clk_create(struct device *dev);
+extern int __pm_clk_create(struct device *dev, struct lock_class_key *key);
 extern void pm_clk_destroy(struct device *dev);
 extern int pm_clk_add(struct device *dev, const char *con_id);
 extern int pm_clk_add_clk(struct device *dev, struct clk *clk);
@@ -45,7 +45,22 @@ extern int of_pm_clk_add_clks(struct device *dev);
 extern void pm_clk_remove_clk(struct device *dev, struct clk *clk);
 extern int pm_clk_suspend(struct device *dev);
 extern int pm_clk_resume(struct device *dev);
-extern int devm_pm_clk_create(struct device *dev);
+extern int __devm_pm_clk_create(struct device *dev, struct lock_class_key *key);
+
+/* Per-call-site lockdep class, as clock mutexes of different devices nest */
+#define pm_clk_create(dev)						\
+({									\
+	static struct lock_class_key __key;				\
+									\
+	__pm_clk_create(dev, &__key);					\
+})
+
+#define devm_pm_clk_create(dev)						\
+({									\
+	static struct lock_class_key __key;				\
+									\
+	__devm_pm_clk_create(dev, &__key);				\
+})
 #else
 static inline bool pm_clk_no_clocks(struct device *dev)
 {
-- 
2.55.0