When atmel_pwm_config() calculates and then sets the prescaler, it is
overwriting the channel's CMR register so we are losing the CPOL configuration.
As atmel_pwm_config() is always called before enabling a channel, inverting the
polarity doesn't work.
Fix that by reading CMR first and only overwriting the prescaler bits.
Signed-off-by: Alexandre Belloni <alexandre.bell...@free-electrons.com>
---
drivers/pwm/pwm-atmel.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index bf4144a14661..2d69e9c431dd 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -32,6 +32,7 @@
/* Bit field in CMR */
#define PWM_CMR_CPOL (1 << 9)
#define PWM_CMR_UPD_CDTY (1 << 10)
+#define PWM_CMR_CPRE_MSK 0xF
/* The following registers for PWM v1 */
#define PWMV1_CDTY 0x04
@@ -104,6 +105,7 @@ static int atmel_pwm_config(struct pwm_chip *chip, struct
pwm_device *pwm,
unsigned long clk_rate, prd, dty;
unsigned long long div;
unsigned int pres = 0;
+ u32 val;
int ret;
if (test_bit(PWMF_ENABLED, &pwm->flags) && (period_ns != pwm->period)) {
@@ -139,7 +141,10 @@ static int atmel_pwm_config(struct pwm_chip *chip, struct
pwm_device *pwm,
return ret;
}
- atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, pres);
+ /* It is necessary to preserve CPOL, inside CMR */
+ val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
+ val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK);
+ atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
atmel_pwm->config(chip, pwm, dty, prd);
clk_disable(atmel_pwm->clk);
--
1.8.3.2
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