[PATCH v2] pwm: atmel: Enable clk when pwm already enabled in bootloader

[Guiting Shen]

The driver would never call clk_enable() if the PWM channel was already
enabled in bootloader which lead to dump the warning message "the PWM
clock already disabled" when turning off the PWM channel.

Add atmel_pwm_enable_clk_if_on() in probe function to enable clock if
the PWM channel was already enabled in bootloader.

Signed-off-by: Guiting Shen <aarongt.shen@xxxxxxxxx>
---
 drivers/pwm/pwm-atmel.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index cdbc23649032..ced4ad3c68b2 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -464,6 +464,31 @@ static const struct of_device_id atmel_pwm_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids);
 
+static int atmel_pwm_enable_clk_if_on(struct atmel_pwm_chip *atmel_pwm)
+{
+	unsigned int i;
+	int err;
+	u32 sr;
+
+	sr = atmel_pwm_readl(atmel_pwm, PWM_SR);
+	if (!sr)
+		return 0;
+
+	for (i = 0; i < atmel_pwm->chip.npwm; i++) {
+		if (!(sr & (1 << i)))
+			continue;
+
+		err = clk_enable(atmel_pwm->clk);
+		if (err) {
+			dev_err(atmel_pwm->chip.dev,
+				"failed to enable clock: %pe\n", ERR_PTR(err));
+			return err;
+		}
+	}
+
+	return 0;
+}
+
 static int atmel_pwm_probe(struct platform_device *pdev)
 {
 	struct atmel_pwm_chip *atmel_pwm;
@@ -496,6 +521,10 @@ static int atmel_pwm_probe(struct platform_device *pdev)
 	atmel_pwm->chip.ops = &atmel_pwm_ops;
 	atmel_pwm->chip.npwm = 4;
 
+	ret = atmel_pwm_enable_clk_if_on(atmel_pwm);
+	if (ret < 0)
+		goto unprepare_clk;
+
 	ret = pwmchip_add(&atmel_pwm->chip);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to add PWM chip %d\n", ret);
-- 
2.25.1