[PATCH] pwm: renesas-tpu: Fix runtime PM reference leak

[PATCH] pwm: renesas-tpu: Fix runtime PM reference leak

[Ruoyu Wang]

tpu_pwm_timer_start() used pm_runtime_get_sync() without checking its
return value before touching the TPU clock.  A failed runtime resume was
therefore ignored, and the callback continued into register access.

Use pm_runtime_resume_and_get() and propagate a failed resume.  Keep the
matching put when clock preparation fails after a successful resume.

tpu_pwm_disable() also needs to propagate a failed start so that the PWM
apply callback does not access registers while runtime PM is inactive.

This issue was found by a static analysis checker and confirmed by manual
source review.

Fixes: 99b82abb0a35 ("pwm: Add Renesas TPU PWM driver")
Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>
---
 drivers/pwm/pwm-renesas-tpu.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/pwm/pwm-renesas-tpu.c b/drivers/pwm/pwm-renesas-tpu.c
index 2196080b41770..c0bbe275275c8 100644
--- a/drivers/pwm/pwm-renesas-tpu.c
+++ b/drivers/pwm/pwm-renesas-tpu.c
@@ -149,10 +149,14 @@ static int tpu_pwm_timer_start(struct tpu_pwm_device *tpd)
 
 	if (!tpd->timer_on) {
 		/* Wake up device and enable clock. */
-		pm_runtime_get_sync(&tpd->tpu->pdev->dev);
+		ret = pm_runtime_resume_and_get(&tpd->tpu->pdev->dev);
+		if (ret < 0)
+			return ret;
+
 		ret = clk_prepare_enable(tpd->tpu->clk);
 		if (ret) {
 			dev_err(&tpd->tpu->pdev->dev, "cannot enable clock\n");
+			pm_runtime_put(&tpd->tpu->pdev->dev);
 			return ret;
 		}
 		tpd->timer_on = true;
@@ -382,15 +386,21 @@ static int tpu_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 	return 0;
 }
 
-static void tpu_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+static int tpu_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct tpu_device *tpu = to_tpu_device(chip);
 	struct tpu_pwm_device *tpd = &tpu->tpd[pwm->hwpwm];
+	int ret;
 
 	/* The timer must be running to modify the pin output configuration. */
-	tpu_pwm_timer_start(tpd);
+	ret = tpu_pwm_timer_start(tpd);
+	if (ret < 0)
+		return ret;
+
 	tpu_pwm_set_pin(tpd, TPU_PIN_INACTIVE);
 	tpu_pwm_timer_stop(tpd);
+
+	return 0;
 }
 
 static int tpu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
@@ -401,7 +411,10 @@ static int tpu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	if (state->polarity != pwm->state.polarity) {
 		if (enabled) {
-			tpu_pwm_disable(chip, pwm);
+			err = tpu_pwm_disable(chip, pwm);
+			if (err)
+				return err;
+
 			enabled = false;
 		}
 
@@ -412,7 +425,7 @@ static int tpu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	if (!state->enabled) {
 		if (enabled)
-			tpu_pwm_disable(chip, pwm);
+			return tpu_pwm_disable(chip, pwm);
 
 		return 0;
 	}
-- 
2.51.0

Re: [PATCH] pwm: renesas-tpu: Fix runtime PM reference leak

[Uwe Kleine-König]

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Hello,

On Fri, Aug 14, 2026 at 09:41:43PM +0800, Ruoyu Wang wrote:
> tpu_pwm_timer_start() used pm_runtime_get_sync() without checking its
> return value before touching the TPU clock.  A failed runtime resume was
> therefore ignored, and the callback continued into register access.
> 
> Use pm_runtime_resume_and_get() and propagate a failed resume.  Keep the
> matching put when clock preparation fails after a successful resume.
> 
> tpu_pwm_disable() also needs to propagate a failed start so that the PWM
> apply callback does not access registers while runtime PM is inactive.
> 
> This issue was found by a static analysis checker and confirmed by manual
> source review.
> 
> Fixes: 99b82abb0a35 ("pwm: Add Renesas TPU PWM driver")
> Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>

Looks good to me. While it's a fix, I think it's not very urgent, we
lived with that since 13 years and is very unlikely to trigger.

So I applied it to

https://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux.git pwm/for-nexxt

as 7.4-rc1 material. This branch isn't written in stone, so I'll still
take acks for the patch, and I will rebase it to 7.3-rc1 once that is
available.

Thanks for your contribution,
Uwe

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