[PATCH AUTOSEL 5.10 17/39] PM: runtime: Clear power.needs_force_resume in pm_runtime_reinit()

[Sasha Levin <sashal@kernel.org>]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

[ Upstream commit 89d9cec3b1e9c49bae9375a2db6dc49bc7468af0 ]

Clear power.needs_force_resume in pm_runtime_reinit() in case it has
been set by pm_runtime_force_suspend() invoked from a driver remove
callback.

Suggested-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://patch.msgid.link/9495163.CDJkKcVGEf@rjwysocki.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

**Backport Status: YES**

This commit is a clear bugfix that should be backported to stable kernel
trees for the following reasons:

1. **It fixes a real bug**: The commit addresses a specific issue where
   `power.needs_force_resume` flag is not cleared in
   `pm_runtime_reinit()` when a device is removed. If a driver calls
   `pm_runtime_force_suspend()` from its remove callback (which sets
   `needs_force_resume = 1`), this flag remains set even after the
   device is removed and potentially re-probed.

2. **The fix is minimal and contained**: The change adds just 5 lines of
   code (including comments) to clear a single flag. The modification
   is:
  ```c
  dev->power.needs_force_resume = false;
  ```
  This is a very low-risk change that only affects the specific
  condition being fixed.

3. **It prevents state leakage**: Looking at the code flow:
   - `pm_runtime_force_suspend()` sets `dev->power.needs_force_resume =
     1` (line in runtime.c)
   - When a driver is removed, `pm_runtime_remove()` calls
     `pm_runtime_reinit()`
   - Without this fix, if the device is re-probed, it would still have
     `needs_force_resume = 1` from the previous instance
   - This could lead to incorrect PM runtime behavior where
     `pm_runtime_force_resume()` would incorrectly think it needs to
     resume a device that was never suspended in the current probe cycle

4. **Related to previous stable fixes**: The git history shows a
   previous commit `c745253e2a69` ("PM: runtime: Fix unpaired parent
   child_count for force_resume") was already marked for stable (4.16+),
   indicating that issues with the `needs_force_resume` flag have been
   problematic enough to warrant stable backports.

5. **Clear bug scenario**: The commit message describes a specific
   scenario where this happens - when `pm_runtime_force_suspend()` is
   called from a driver remove callback. This is a legitimate use case
   where drivers want to ensure devices are suspended before removal.

6. **No architectural changes**: This is purely a bugfix that clears a
   flag that should have been cleared during reinitialization. It
   doesn't introduce new features or change any APIs.

The fix ensures proper PM runtime state management across device removal
and re-probing cycles, which is important for system stability and
correct power management behavior.

 drivers/base/power/runtime.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 58d376b1cd68..7e912d2ed427 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1716,6 +1716,11 @@ void pm_runtime_reinit(struct device *dev)
 				pm_runtime_put(dev->parent);
 		}
 	}
+	/*
+	 * Clear power.needs_force_resume in case it has been set by
+	 * pm_runtime_force_suspend() invoked from a driver remove callback.
+	 */
+	dev->power.needs_force_resume = false;
 }
 
 /**
-- 
2.39.5