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

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>
Fixes: 738a1cf ("pwm: Add i.MX TPM PWM driver support")
Link: https://patch.msgid.link/20260311123309.348904-1-viorel.suman@oss.nxp.com
Cc: stable@vger.kernel.org
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

Author: ViorelSuman

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");