[PATCH v4] 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 at gmail.com>
---
 drivers/pwm/pwm-atmel.c | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index cdbc23649032..28ea0f7267ca 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -36,7 +36,7 @@
 #define PWM_SR			0x0C
 #define PWM_ISR			0x1C
 /* Bit field in SR */
-#define PWM_SR_ALL_CH_ON	0x0F
+#define PWM_SR_ALL_CH_MASK	0x0F
 
 /* The following register is PWM channel related registers */
 #define PWM_CH_REG_OFFSET	0x200
@@ -464,6 +464,37 @@ 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 & PWM_SR_ALL_CH_MASK))
+		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 for pwm #%d: %pe\n",
+							i, ERR_PTR(err));
+
+			while (i--) {
+				if (sr & (1 << i))
+					clk_disable(atmel_pwm->clk);
+			}
+			return err;
+		}
+	}
+
+	return 0;
+}
+
 static int atmel_pwm_probe(struct platform_device *pdev)
 {
 	struct atmel_pwm_chip *atmel_pwm;
@@ -504,8 +535,15 @@ static int atmel_pwm_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, atmel_pwm);
 
+	ret = atmel_pwm_enable_clk_if_on(atmel_pwm);
+	if (ret < 0)
+		goto remove_pwmchip;
+
 	return ret;
 
+remove_pwmchip:
+	pwmchip_remove(&atmel_pwm->chip);
+
 unprepare_clk:
 	clk_unprepare(atmel_pwm->clk);
 	return ret;
-- 
2.25.1