[PATCH] hwrng: atmel: fix usage_count leak when autosuspend_delay is negative

[Guangshuo Li]

atmel_trng_probe() calls pm_runtime_use_autosuspend(), but neither the
probe failure path nor atmel_trng_remove() calls the matching
pm_runtime_dont_use_autosuspend() before disabling runtime PM.

If the autosuspend delay is set to a negative value while autosuspend
is enabled, the runtime PM core increments usage_count to prevent
runtime suspend. Without calling pm_runtime_dont_use_autosuspend()
during teardown, this reference is not dropped and usage_count remains
unbalanced.

Add the missing pm_runtime_dont_use_autosuspend() calls to both the
probe failure and remove paths before disabling runtime PM.

This issue was found by manual code inspection.

Fixes: c4f51eab6ce0 ("hwrng: atmel - add runtime pm support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
---
 drivers/char/hw_random/atmel-rng.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/char/hw_random/atmel-rng.c b/drivers/char/hw_random/atmel-rng.c
index 4ebbc44fecf0..6265d9a8d140 100644
--- a/drivers/char/hw_random/atmel-rng.c
+++ b/drivers/char/hw_random/atmel-rng.c
@@ -150,6 +150,7 @@ static int atmel_trng_probe(struct platform_device *pdev)
 
 	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
 	if (ret) {
+		pm_runtime_dont_use_autosuspend(&pdev->dev);
 		pm_runtime_disable(&pdev->dev);
 		pm_runtime_set_suspended(&pdev->dev);
 #ifndef CONFIG_PM
@@ -165,6 +166,7 @@ static void atmel_trng_remove(struct platform_device *pdev)
 	struct atmel_trng *trng = platform_get_drvdata(pdev);
 
 	atmel_trng_cleanup(trng);
+	pm_runtime_dont_use_autosuspend(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 	pm_runtime_set_suspended(&pdev->dev);
 }
-- 
2.43.0