[PATCH v4] pwm: atmel: Enable clk when pwm already enabled in bootloader

From: Guiting Shen
Date: Wed Jul 12 2023 - 09:44:12 EST


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 | 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