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authorAlexandre Belloni <alexandre.belloni@free-electrons.com>2014-03-14 15:19:08 +0100
committerThierry Reding <thierry.reding@gmail.com>2014-03-18 20:47:31 +0100
commit8db9e29fe540c9640ea60f37ecf99d3a73bd12c5 (patch)
treed7458bb791e71432ad12fe47aa9380d78830733f /drivers/pwm/pwm-atmel.c
parent42586315b7b6e682bd4136a1a2bc2b1d50113487 (diff)
downloadlinux-8db9e29fe540c9640ea60f37ecf99d3a73bd12c5.tar.bz2
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>
Diffstat (limited to 'drivers/pwm/pwm-atmel.c')
-rw-r--r--drivers/pwm/pwm-atmel.c7
1 files changed, 6 insertions, 1 deletions
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);