linux-kernel - Re: [PATCH] pwm: imx-tpm: keep channel state instead of counting

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Message-ID: <aXztQkefafsgFJvN@lizhi-Precision-Tower-5810>
Date: Fri, 30 Jan 2026 12:41:22 -0500
From: Frank Li <Frank.li@....com>
To: "Viorel Suman (OSS)" <viorel.suman@....nxp.com>
Cc: Uwe Kleine-König <ukleinek@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, linux-pwm@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pwm: imx-tpm: keep channel state instead of counting

On Fri, Jan 30, 2026 at 04:37:20PM +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 this problem by replacing counting logic with per-channel state handling.
>
> Signed-off-by: Viorel Suman (OSS) <viorel.suman@....nxp.com>
> ---
>  drivers/pwm/pwm-imx-tpm.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
> index 5b399de16d60..0f8643f4a70b 100644
> --- a/drivers/pwm/pwm-imx-tpm.c
> +++ b/drivers/pwm/pwm-imx-tpm.c
> @@ -62,7 +62,7 @@ struct imx_tpm_pwm_chip {
>  	void __iomem *base;
>  	struct mutex lock;
>  	u32 user_count;
> -	u32 enable_count;
> +	u32 enabled_channels;
>  	u32 real_period;
>  };
>
> @@ -166,6 +166,10 @@ static int pwm_imx_tpm_get_state(struct pwm_chip *chip,
>
>  	/* get channel status */
>  	state->enabled = FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val) ? true : false;
> +	if (state->enabled)
> +		tpm->enabled_channels |= BIT(pwm->hwpwm);
> +	else
> +		tpm->enabled_channels &= ~BIT(pwm->hwpwm);

Do you have lock for RMW? or you should atomic_or() and atomic_and()

Frank

>
>  	return 0;
>  }
> @@ -282,15 +286,19 @@ static int pwm_imx_tpm_apply_hw(struct pwm_chip *chip,
>  	}
>  	writel(val, tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));
>
> -	/* control the counter status */
> +	/* control the channel state */
>  	if (state->enabled != c.enabled) {
>  		val = readl(tpm->base + PWM_IMX_TPM_SC);
>  		if (state->enabled) {
> -			if (++tpm->enable_count == 1)
> +			if (tpm->enabled_channels == 0) {
>  				val |= PWM_IMX_TPM_SC_CMOD_INC_EVERY_CLK;
> +			}
> +			tpm->enabled_channels |= BIT(pwm->hwpwm);
>  		} else {
> -			if (--tpm->enable_count == 0)
> +			tpm->enabled_channels &= ~BIT(pwm->hwpwm);
> +			if (tpm->enabled_channels == 0) {
>  				val &= ~PWM_IMX_TPM_SC_CMOD;
> +			}
>  		}
>  		writel(val, tpm->base + PWM_IMX_TPM_SC);
>  	}
> @@ -394,7 +402,7 @@ static int pwm_imx_tpm_suspend(struct device *dev)
>  	struct imx_tpm_pwm_chip *tpm = dev_get_drvdata(dev);
>  	int ret;
>
> -	if (tpm->enable_count > 0)
> +	if (tpm->enabled_channels > 0)
>  		return -EBUSY;
>
>  	/*
> --
> 2.34.1
>