[PATCH] clocksource: add devm_clocksource_register_*() helpers

[Daniel Lezcano]

Introduce device-managed helpers for clocksource registration.

The clocksource framework currently provides
__clocksource_register_scale() along with convenience wrappers for Hz
and kHz registration. However, drivers must handle error paths and
cleanup manually, typically by pairing registration with an explicit
clocksource_unregister() call.

Add a devm-based variant, __devm_clocksource_register_scale(), along
with devm_clocksource_register_hz() and
devm_clocksource_register_khz() helpers.

These helpers register the clocksource and attach a devres action to
automatically unregister it on driver detach or probe failure.

This simplifies driver code by:

* removing explicit cleanup paths
* ensuring correct teardown ordering
* aligning with the devm-based resource management model widely used
  across the kernel

While drivers can open-code devm_add_action_or_reset(), providing a
dedicated helper avoids duplication, reduces boilerplate, and ensures
consistent usage across drivers, following patterns used in other
subsystems.

This is also particularly useful for drivers built as modules, where
device-managed resource handling avoids manual cleanup in remove paths
and ensures correct teardown on module unload.

This helper is self-contained and can be adopted progressively by
drivers.

No functional change.

Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
---
 include/linux/clocksource.h | 15 +++++++++++++++
 kernel/time/clocksource.c   | 20 ++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 7c38190b10bf..c5b34c16602e 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -236,6 +236,9 @@ clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
  */
 extern int
 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
+extern int
+__devm_clocksource_register_scale(struct device *dev, struct clocksource *cs,
+				  u32 scale, u32 freq);
 extern void
 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
 
@@ -258,6 +261,18 @@ static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 	return __clocksource_register_scale(cs, 1000, khz);
 }
 
+static inline int devm_clocksource_register_hz(struct device *dev,
+					       struct clocksource *cs, u32 hz)
+{
+	return __devm_clocksource_register_scale(dev, cs, 1, hz);
+}
+
+static inline int devm_clocksource_register_khz(struct device *dev,
+						struct clocksource *cs, u32 khz)
+{
+	return __devm_clocksource_register_scale(dev, cs, 1000, khz);
+}
+
 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
 {
 	__clocksource_update_freq_scale(cs, 1, hz);
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index baee13a1f87f..313f6c88148e 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -1338,6 +1338,26 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
 }
 EXPORT_SYMBOL_GPL(__clocksource_register_scale);
 
+static void __devm_clocksource_unregister(void *data)
+{
+	struct clocksource *cs = data;
+
+	clocksource_unregister(cs);
+}
+
+int __devm_clocksource_register_scale(struct device *dev, struct clocksource *cs,
+				      u32 scale, u32 freq)
+{
+	int ret;
+
+	ret = __clocksource_register_scale(cs, scale, freq);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev, __devm_clocksource_unregister, cs);
+}
+EXPORT_SYMBOL_GPL(__devm_clocksource_register_scale);
+
 /*
  * Unbind clocksource @cs. Called with clocksource_mutex held
  */
-- 
2.43.0