[PATCH 6.1.y] pwm: imx-tpm: Count the number of enabled channels in probe

[Sasha Levin <sashal@kernel.org>]

From: "Viorel Suman (OSS)" <viorel.suman@oss.nxp.com>

[ Upstream commit 3962c24f2d14e8a7f8a23f56b7ce320523947342 ]

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: 738a1cfec2ed ("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>
[ substituted `base` with `tpm->base` and `npwm` with `tpm->chip.npwm` to match the older non-devm probe layout ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pwm/pwm-imx-tpm.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
index 081f511cd2130..e1caaef7dbd16 100644
--- a/drivers/pwm/pwm-imx-tpm.c
+++ b/drivers/pwm/pwm-imx-tpm.c
@@ -350,6 +350,7 @@ static int pwm_imx_tpm_probe(struct platform_device *pdev)
 {
 	struct imx_tpm_pwm_chip *tpm;
 	int ret;
+	unsigned int i;
 	u32 val;
 
 	tpm = devm_kzalloc(&pdev->dev, sizeof(*tpm), GFP_KERNEL);
@@ -383,6 +384,13 @@ static int pwm_imx_tpm_probe(struct platform_device *pdev)
 
 	mutex_init(&tpm->lock);
 
+	/* count the enabled channels */
+	for (i = 0; i < tpm->chip.npwm; ++i) {
+		val = readl(tpm->base + PWM_IMX_TPM_CnSC(i));
+		if (FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val))
+			++tpm->enable_count;
+	}
+
 	ret = pwmchip_add(&tpm->chip);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
-- 
2.53.0