Re: [PATCH 1/5] gpio: mvebu: fix pwm get_state period calculation

[Baruch Siach <baruch@xxxxxxxxxx>]

Hi Uwe,

On Mon, Jan 11 2021, Uwe Kleine-König wrote:
> $Subject ~= s/get_state/.get_state/ ?

Ack.

> On Mon, Jan 11, 2021 at 01:17:02PM +0200, Baruch Siach wrote:
>> The period is the sum of on and off values.
>> 
>> Reported-by: Russell King <linux@xxxxxxxxxxxxxxx>
>> Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support")
>> Signed-off-by: Baruch Siach <baruch@xxxxxxxxxx>
>> ---
>>  drivers/gpio/gpio-mvebu.c | 19 ++++++++-----------
>>  1 file changed, 8 insertions(+), 11 deletions(-)
>> 
>> diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
>> index 672681a976f5..a912a8fed197 100644
>> --- a/drivers/gpio/gpio-mvebu.c
>> +++ b/drivers/gpio/gpio-mvebu.c
>> @@ -676,20 +676,17 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip,
>>  	else
>>  		state->duty_cycle = 1;
>>  
>> +	val = (unsigned long long) u; /* on duration */
>>  	regmap_read(mvpwm->regs, mvebu_pwmreg_blink_off_duration(mvpwm), &u);
>> -	val = (unsigned long long) u * NSEC_PER_SEC;
>> +	val += (unsigned long long) u; /* period = on + off duration */
>> +	val *= NSEC_PER_SEC;
>>  	do_div(val, mvpwm->clk_rate);
>> -	if (val < state->duty_cycle) {
>> +	if (val > UINT_MAX)
>> +		state->period = UINT_MAX;
>> +	else if (val)
>> +		state->period = val;
>> +	else
>>  		state->period = 1;
>> -	} else {
>> -		val -= state->duty_cycle;
>> -		if (val > UINT_MAX)
>> -			state->period = UINT_MAX;
>> -		else if (val)
>> -			state->period = val;
>> -		else
>> -			state->period = 1;
>> -	}
>
> The patch looks good, the patch description could be a bit more verbose.
> Something like:
>
> 	Calculate the period as
>
> 		($on + $off) / clkrate
>
> 	instead of
>
> 		$off / clkrate - $on / clkrate
>
> 	.

I take this to refer to the next patch (2/5). This patch changes from
buggy

  $on / clkrate

to

  ($on + $off) / clkrate

baruch

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