On Fri Jan 17, 2025 at 10:33 AM CET, Uwe Kleine-König wrote:
> Hello Mathieu,
>
> On Mon, Jan 13, 2025 at 01:42:27PM +0100, mathieu.dubois-briand@xxxxxxxxxxx wrote:
> > From: Kamel Bouhara <kamel.bouhara@xxxxxxxxxxx>
...
> > +static int max7360_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > + const struct pwm_state *state)
> > +{
> > + struct max7360_pwm *max7360_pwm;
> > + u64 duty_steps;
> > + int ret;
> > +
> > + if (state->polarity != PWM_POLARITY_NORMAL)
> > + return -EINVAL;
> > +
> > + if (state->period != MAX7360_PWM_PERIOD_NS) {
> > + dev_warn(&chip->dev,
> > + "unsupported pwm period: %llu, should be %u\n",
> > + state->period, MAX7360_PWM_PERIOD_NS);
> > + return -EINVAL;
>
> Please don't emit error messages in .apply(). Also a driver is supposed
> to round down .period, so any value >= MAX7360_PWM_PERIOD_NS should be
> accepted.
>
> Also note that you might want to implement the waveform callbacks
> instead of .apply() and .get_state() for the more modern abstraction
> (with slightly different rounding rules).
>
Sure, I just switched to the waveform callbacks, it was quite
straightforward.
> > +static int max7360_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> > + struct pwm_state *state)
> > +{
...
> > + state->duty_cycle = mul_u64_u64_div_u64(val, MAX7360_PWM_PERIOD_NS,
> > + MAX7360_PWM_MAX_RES);
>
> You have to round up here. I would expect that the checks in the core
> (with PWM_DEBUG=1) help you catching this type of error. In your case
> changing the configuration to
>
> .period = 2000000,
> .duty_cycle = 234379,
>
> should yield some hint in the kernel log.
>
Thanks for the reproduce steps: I saw the bug and fixed it. Also
MAX7360_PWM_MAX_RES had to be set to 255 and not 256...
> > + return 0;
> > +}
>
> Best regards
> Uwe
I also fixed all other points mentioned in your mail. Thanks again for your review.
--
Mathieu Dubois-Briand, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
