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

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Message-Id: <20260130143720.778514-1-viorel.suman@oss.nxp.com>
Date: Fri, 30 Jan 2026 16:37:20 +0200
From: "Viorel Suman (OSS)" <viorel.suman@....nxp.com>
To: Uwe Kleine-König <ukleinek@...nel.org>,
	Frank Li <Frank.Li@....com>,
	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
Cc: Viorel Suman <viorel.suman@....nxp.com>
Subject: [PATCH] pwm: imx-tpm: keep channel state instead of counting

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);
 
 	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