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pwm: atmel: Fix polarity handling 

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.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Alexandre Belloni 2014-03-14 15:19:08 +01:00 committed by Thierry Reding
parent 42586315b7
commit 8db9e29fe5
1 changed files with 6 additions and 1 deletions
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7
drivers/pwm/pwm-atmel.c
View File

@ -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);