On 29/09/2013 12:12, Bo Shen wrote:
> Hi Alexandre,
>
> On 9/28/2013 04:10, Alexandre Belloni wrote:
>> I found that disabling a pwm while it is at a low level will actually
>> put it
>> back at a high level. The main symptom is that leds-pwm is calling
>> pwm_disable()
>> after setting the duty cycle to 0. Hence, instead of getting a
>> switched off LED,
>> you get an LED lit up at full brightness.
>>
>> Solve that by using the request and free callbacks to enable and
>> disable the
>> pwm channels and the clock.
>>
>> Signed-off-by: Alexandre Belloni <alexandre.bell...@free-electrons.com>
>> ---
>>
>> This patch applies after:
>> [PATCH v4] PWM: atmel-pwm: add PWM controller driver
>>
>> drivers/pwm/pwm-atmel.c | 14 +++++---------
>> 1 file changed, 5 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
>> index 6af7a50..4526e71 100644
>> --- a/drivers/pwm/pwm-atmel.c
>> +++ b/drivers/pwm/pwm-atmel.c
>> @@ -209,7 +209,7 @@ static int atmel_pwm_set_polarity(struct pwm_chip
>> *chip, struct pwm_device *pwm,
>> return 0;
>> }
>>
>> -static int atmel_pwm_enable(struct pwm_chip *chip, struct pwm_device
>> *pwm)
>> +static int atmel_pwm_request(struct pwm_chip *chip, struct
>> pwm_device *pwm)
>> {
>> struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
>> int ret;
>> @@ -225,23 +225,19 @@ static int atmel_pwm_enable(struct pwm_chip
>> *chip, struct pwm_device *pwm)
>> return 0;
>> }
>>
>> -static void atmel_pwm_disable(struct pwm_chip *chip, struct
>> pwm_device *pwm)
>> +static void atmel_pwm_free(struct pwm_chip *chip, struct pwm_device
>> *pwm)
>> {
>> struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
>> - u32 val;
>>
>> atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm);
>> -
>> - val = atmel_pwm_readl(atmel_pwm, PWM_SR);
>> - if ((val & PWM_SR_ALL_CH_ON) == 0)
>> - clk_disable(atmel_pwm->clk);
>> + clk_disable(atmel_pwm->clk);
>> }
>>
>> static const struct pwm_ops atmel_pwm_ops = {
>> .config = atmel_pwm_config,
>> .set_polarity = atmel_pwm_set_polarity,
>> - .enable = atmel_pwm_enable,
>> - .disable = atmel_pwm_disable,
>> + .request = atmel_pwm_request,
>> + .free = atmel_pwm_free,
>
> This will cause pwmadd_chip failure.
>
> Code from <drivers/pwm/core.c>, in function: pwmadd_chip()
> ---8>---
> if (!chip || !chip->dev || !chip->ops || !chip->ops->config ||
> !chip->ops->enable || !chip->ops->disable)
> return -EINVAL;
> ---<8---
>
You are right, I tested with dummy pwm_enable/pwm_disable functions and
removed them before sending the patch, thinking they weren't needed.
I'll respin that patch.
>> .owner = THIS_MODULE,
>> };
>>
>
> Best Regards,
> Bo Shen
>
--
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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