Re: [PATCH v6] staging: greybus: introduce pwm_ops::apply

[chensong <chensong_2000@189.cn>]

hi Alex,

On 2022/3/18 下午8:15, Alex Elder wrote:
> On 3/18/22 4:57 AM, Song Chen wrote:
>> Introduce newer .apply function in pwm_ops to replace legacy operations
>> including enable, disable, config and set_polarity.
>>
>> This guarantees atomic changes of the pwm controller configuration.
>>
>> Signed-off-by: Song Chen <chensong_2000@189.cn>
> 
> I had another comment suggestion but you've been through enough.
> Thanks for working this to completion.

sorry about that, i probably missed it somehow. Thanks for the 
understanding.

Song

> 
> Reviewed-by: Alex Elder <elder@linaro.org>
> 
>>
>> ---
>> v2:
>> 1, define duty_cycle and period as u64 in gb_pwm_config_operation.
>> 2, define duty and period as u64 in gb_pwm_config_request.
>> 3, disable before configuring duty and period if the eventual goal
>>     is a disabled state.
>>
>> v3:
>> Regarding duty_cycle and period, I read more discussion in this thread,
>> min, warn or -EINVAL, seems no perfect way acceptable for everyone.
>> How about we limit their value to INT_MAX and throw a warning at the
>> same time when they are wrong?
>>
>> v4:
>> 1, explain why legacy operations are replaced.
>> 2, cap the value of period and duty to U32_MAX.
>>
>> v5:
>> 1, revise commit message.
>>
>> v6:
>> 1, revise commit message.
>> 2, explain why capping the value of period and duty to U32_MAX in
>>     comment.
>> ---
>>   drivers/staging/greybus/pwm.c | 64 ++++++++++++++++++++++-------------
>>   1 file changed, 40 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/staging/greybus/pwm.c 
>> b/drivers/staging/greybus/pwm.c
>> index 891a6a672378..ad20ec24031e 100644
>> --- a/drivers/staging/greybus/pwm.c
>> +++ b/drivers/staging/greybus/pwm.c
>> @@ -204,43 +204,59 @@ static void gb_pwm_free(struct pwm_chip *chip, 
>> struct pwm_device *pwm)
>>       gb_pwm_deactivate_operation(pwmc, pwm->hwpwm);
>>   }
>> -static int gb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>> -             int duty_ns, int period_ns)
>> +static int gb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>> +            const struct pwm_state *state)
>>   {
>> +    int err;
>> +    bool enabled = pwm->state.enabled;
>> +    u64 period = state->period;
>> +    u64 duty_cycle = state->duty_cycle;
>>       struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
>> -    return gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_ns, 
>> period_ns);
>> -};
>> +    /* Set polarity */
>> +    if (state->polarity != pwm->state.polarity) {
>> +        if (enabled) {
>> +            gb_pwm_disable_operation(pwmc, pwm->hwpwm);
>> +            enabled = false;
>> +        }
>> +        err = gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, 
>> state->polarity);
>> +        if (err)
>> +            return err;
>> +    }
>> -static int gb_pwm_set_polarity(struct pwm_chip *chip, struct 
>> pwm_device *pwm,
>> -                   enum pwm_polarity polarity)
>> -{
>> -    struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
>> +    if (!state->enabled) {
>> +        if (enabled)
>> +            gb_pwm_disable_operation(pwmc, pwm->hwpwm);
>> +        return 0;
>> +    }
>> -    return gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, polarity);
>> -};
>> +    /*
>> +     * Set period and duty cycle
>> +     *
>> +     * PWM privodes 64-bit period and duty_cycle, but greybus only 
>> accepts
>> +     * 32-bit, so their values have to be limited to U32_MAX.
>> +     */
>> +    if (period > U32_MAX)
>> +        period = U32_MAX;
>> -static int gb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
>> -{
>> -    struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
>> +    if (duty_cycle > period)
>> +        duty_cycle = period;
>> -    return gb_pwm_enable_operation(pwmc, pwm->hwpwm);
>> -};
>> +    err = gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_cycle, period);
>> +    if (err)
>> +        return err;
>> -static void gb_pwm_disable(struct pwm_chip *chip, struct pwm_device 
>> *pwm)
>> -{
>> -    struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
>> +    /* enable/disable */
>> +    if (!enabled)
>> +        return gb_pwm_enable_operation(pwmc, pwm->hwpwm);
>> -    gb_pwm_disable_operation(pwmc, pwm->hwpwm);
>> -};
>> +    return 0;
>> +}
>>   static const struct pwm_ops gb_pwm_ops = {
>>       .request = gb_pwm_request,
>>       .free = gb_pwm_free,
>> -    .config = gb_pwm_config,
>> -    .set_polarity = gb_pwm_set_polarity,
>> -    .enable = gb_pwm_enable,
>> -    .disable = gb_pwm_disable,
>> +    .apply = gb_pwm_apply,
>>       .owner = THIS_MODULE,
>>   };
> 
>