pwm-leds calls .config() and .disable() in a row. This exhibits that it may happen that the channel gets disabled before CDTY has been updated with CUPD. The issue gets quite worse with long periods. So, ensure that at least one period has past before disabling the channel by polling ISR.
Signed-off-by: Alexandre Belloni <[email protected]> --- drivers/pwm/pwm-atmel.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c index 89f9ca41d9af..054db5aacd7a 100644 --- a/drivers/pwm/pwm-atmel.c +++ b/drivers/pwm/pwm-atmel.c @@ -8,6 +8,7 @@ */ #include <linux/clk.h> +#include <linux/delay.h> #include <linux/err.h> #include <linux/io.h> #include <linux/module.h> @@ -21,6 +22,7 @@ #define PWM_ENA 0x04 #define PWM_DIS 0x08 #define PWM_SR 0x0C +#define PWM_ISR 0x1C /* Bit field in SR */ #define PWM_SR_ALL_CH_ON 0x0F @@ -243,6 +245,17 @@ static int atmel_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm) static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm) { struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip); + unsigned long timeout = jiffies + 2 * HZ; + + /* + * Wait for at least a complete period to have passed before disabling a + * channel to be sure that CDTY has been updated + */ + atmel_pwm_readl(atmel_pwm, PWM_ISR); + + while (!(atmel_pwm_readl(atmel_pwm, PWM_ISR) & (1 << pwm->hwpwm)) && + time_before(jiffies, timeout)) + usleep_range(10, 100); atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm); -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
