pwm: imx-tpm: count the number of enabled channels in probe

[PATCH v3] pwm: imx-tpm: count the number of enabled channels in probe

Posted by Viorel Suman (OSS) 3 weeks, 6 days ago

On a soft reset TPM PWM IP may preserve its internal state from
previous runtime, therefore on a subsequent OS boot and driver
probe "enable_count" value and TPM PWM IP internal channels
"enabled" states may get unaligned. In consequence on a suspend/resume
cycle the call "if (--tpm->enable_count == 0)" may lead to
"enable_count" overflow the system being blocked from entering
suspend due to:

   if (tpm->enable_count > 0)
       return -EBUSY;

Fix the problem by counting the enabled channels in probe function.

Signed-off-by: Viorel Suman (OSS) <viorel.suman@oss.nxp.com>
---
 drivers/pwm/pwm-imx-tpm.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
index 5b399de16d60..80fdb3303400 100644
--- a/drivers/pwm/pwm-imx-tpm.c
+++ b/drivers/pwm/pwm-imx-tpm.c
@@ -352,7 +352,7 @@ static int pwm_imx_tpm_probe(struct platform_device *pdev)
 	struct clk *clk;
 	void __iomem *base;
 	int ret;
-	unsigned int npwm;
+	unsigned int i, npwm;
 	u32 val;
 
 	base = devm_platform_ioremap_resource(pdev, 0);
@@ -382,6 +382,13 @@ static int pwm_imx_tpm_probe(struct platform_device *pdev)
 
 	mutex_init(&tpm->lock);
 
+	/* count the enabled channels */
+	for (i = 0; i < npwm; ++i) {
+		val = readl(base + PWM_IMX_TPM_CnSC(i));
+		if (FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val))
+			++tpm->enable_count;
+	}
+
 	ret = devm_pwmchip_add(&pdev->dev, chip);
 	if (ret)
 		return dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");
-- 
2.34.1

Re: [PATCH v3] pwm: imx-tpm: count the number of enabled channels in probe

Posted by Uwe Kleine-König 3 weeks, 4 days ago

Hello,

On Wed, Mar 11, 2026 at 02:33:09PM +0200, Viorel Suman (OSS) wrote:
> On a soft reset TPM PWM IP may preserve its internal state from
> previous runtime, therefore on a subsequent OS boot and driver
> probe "enable_count" value and TPM PWM IP internal channels
> "enabled" states may get unaligned. In consequence on a suspend/resume
> cycle the call "if (--tpm->enable_count == 0)" may lead to
> "enable_count" overflow the system being blocked from entering
> suspend due to:
> 
>    if (tpm->enable_count > 0)
>        return -EBUSY;
> 
> Fix the problem by counting the enabled channels in probe function.
> 
> Signed-off-by: Viorel Suman (OSS) <viorel.suman@oss.nxp.com>

Applied to
https://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux.git pwm/for-next

with Cc: stable. Given that the issue is already old (May 2019 in
5.2-rc1) I tend to not send it for inclusion into v7.0, but if something
more urgent pops up I'll probably send it along.

Best regards
Uwe

Re: [PATCH v3] pwm: imx-tpm: count the number of enabled channels in probe

Posted by Frank Li 3 weeks, 6 days ago

On Wed, Mar 11, 2026 at 02:33:09PM +0200, Viorel Suman (OSS) wrote:
> On a soft reset TPM PWM IP may preserve its internal state from
> previous runtime, therefore on a subsequent OS boot and driver
> probe "enable_count" value and TPM PWM IP internal channels
> "enabled" states may get unaligned. In consequence on a suspend/resume
> cycle the call "if (--tpm->enable_count == 0)" may lead to
> "enable_count" overflow the system being blocked from entering
> suspend due to:
>
>    if (tpm->enable_count > 0)
>        return -EBUSY;
>
> Fix the problem by counting the enabled channels in probe function.

Fix tag here

Frank
>
> Signed-off-by: Viorel Suman (OSS) <viorel.suman@oss.nxp.com>
> ---
>  drivers/pwm/pwm-imx-tpm.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
> index 5b399de16d60..80fdb3303400 100644
> --- a/drivers/pwm/pwm-imx-tpm.c
> +++ b/drivers/pwm/pwm-imx-tpm.c
> @@ -352,7 +352,7 @@ static int pwm_imx_tpm_probe(struct platform_device *pdev)
>  	struct clk *clk;
>  	void __iomem *base;
>  	int ret;
> -	unsigned int npwm;
> +	unsigned int i, npwm;
>  	u32 val;
>
>  	base = devm_platform_ioremap_resource(pdev, 0);
> @@ -382,6 +382,13 @@ static int pwm_imx_tpm_probe(struct platform_device *pdev)
>
>  	mutex_init(&tpm->lock);
>
> +	/* count the enabled channels */
> +	for (i = 0; i < npwm; ++i) {
> +		val = readl(base + PWM_IMX_TPM_CnSC(i));
> +		if (FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val))
> +			++tpm->enable_count;
> +	}
> +
>  	ret = devm_pwmchip_add(&pdev->dev, chip);
>  	if (ret)
>  		return dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");
> --
> 2.34.1
>

Re: [PATCH v3] pwm: imx-tpm: count the number of enabled channels in probe

Posted by Uwe Kleine-König 3 weeks, 6 days ago

On Wed, Mar 11, 2026 at 11:35:10AM -0400, Frank Li wrote:
> On Wed, Mar 11, 2026 at 02:33:09PM +0200, Viorel Suman (OSS) wrote:
> > On a soft reset TPM PWM IP may preserve its internal state from
> > previous runtime, therefore on a subsequent OS boot and driver
> > probe "enable_count" value and TPM PWM IP internal channels
> > "enabled" states may get unaligned. In consequence on a suspend/resume
> > cycle the call "if (--tpm->enable_count == 0)" may lead to
> > "enable_count" overflow the system being blocked from entering
> > suspend due to:
> >
> >    if (tpm->enable_count > 0)
> >        return -EBUSY;
> >
> > Fix the problem by counting the enabled channels in probe function.
> 
> Fix tag here

No need to resend just for that. I'll add

Fixes: 738a1cfec2ed ("pwm: Add i.MX TPM PWM driver support")
Cc: stable@vger.kernel.org

when committing.

Thanks
Uwe