[PATCH v2 0/2] PM: clk: Release clocks across runtime suspend

[Loic Poulain <loic.poulain@oss.qualcomm.com>]

pm_clk prepares each clock when it is acquired and keeps that reference
until the entry is removed, runtime suspend only dropping the enable
reference. A prepare reference propagates to the parents though, so a
leaf clock can pin an ancestor that only implements prepare/unprepare
for as long as the device exists. On Qualcomm platforms this is how the
RPM XO clock stays active across runtime and system suspend even though
all of its consumers are suspended.

Drivers that manage their own clock usually unprepare in runtime suspend
245 clk_disable_unprepare() call sites under drivers/ against 27 that
only disable. pm_clk is the outlier, and only because it cannot
sleep for a device that suspends with interrupts disabled. So rather
than asking each clock whether it must sleep, ask the device whether it
may.

Patch 1 derives the locking from pm_runtime_is_irq_safe() and drops
the bookkeeping, patch 2 then unprepares on suspend. IRQ-safe devices
keep the current behaviour.

A non-IRQ-safe device now prepares and unprepares on every runtime PM
cycle rather than once per lifetime.

Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
Changes in v2:
- Split into two patches: the locking rework, then the unprepare on
  suspend.
- Keep clk_is_enabled_when_prepared() in pm_clk_acquire(). v1 used
  dev->power.irq_safe there, which runs before probe() can call
  pm_runtime_irq_safe(), so the flag always read false.
- Drop the clock_op_might_sleep count, the pm_clk_op_lock() retry loop
  and the caller name argument.
- Reject an IRQ-safe device holding a clock that is enabled when
  prepared in __pm_clk_enable() rather than from an in_atomic() test in
  the locking helper.
- Link to v1: https://lore.kernel.org/r/20261030-clk-leak-v1-1-db8cb68a5a8d@oss.qualcomm.com

---
Loic Poulain (2):
      PM: clk: Derive PM clock locking from the device's IRQ safety
      PM: clk: Release the clock prepare reference across runtime suspend

 drivers/base/power/clock_ops.c | 145 +++++++++++++++++++----------------------
 include/linux/pm.h             |   1 -
 2 files changed, 68 insertions(+), 78 deletions(-)
---
base-commit: e726cf08ee6ba7e8b852c77760f12c59f90f1338
change-id: 20261030-clk-leak-3ea6f7c7da25

Best regards,
-- 
Loic Poulain <loic.poulain@oss.qualcomm.com>