Re: [PATCH v2 3/6] pwm: jz4740: Apply configuration atomically

Uwe Kleine-König
2019-07-22T19:35:06Z

Hello Paul,

On Fri, Jun 07, 2019 at 05:44:07PM +0200, Paul Cercueil wrote:
> -static int jz4740_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> - int duty_ns, int period_ns)
> +static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> + struct pwm_state *state)
> {
> struct jz4740_pwm_chip *jz4740 = to_jz4740(pwm->chip);
> unsigned long long tmp;
> unsigned long period, duty;
> unsigned int prescaler = 0;
> uint16_t ctrl;
> - bool is_enabled;
>
> - tmp = (unsigned long long)clk_get_rate(jz4740->clk) * period_ns;
> + tmp = (unsigned long long)clk_get_rate(jz4740->clk) * state->period;
> do_div(tmp, 1000000000);
> period = tmp;
>
> @@ -96,16 +95,14 @@ static int jz4740_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> if (prescaler == 6)
> return -EINVAL;
>
> - tmp = (unsigned long long)period * duty_ns;
> - do_div(tmp, period_ns);
> + tmp = (unsigned long long)period * state->duty_cycle;
> + do_div(tmp, state->period);
> duty = period - tmp;
>
> if (duty >= period)
> duty = period - 1;
>
> - is_enabled = jz4740_timer_is_enabled(pwm->hwpwm);
> - if (is_enabled)
> - jz4740_pwm_disable(chip, pwm);
> + jz4740_pwm_disable(chip, pwm);

I assume this stops the PWM. Does this complete the currently running
period? How does the PWM behave then? (Does it still drive the output?
If so, on which level?)

>
> jz4740_timer_set_count(pwm->hwpwm, 0);
> jz4740_timer_set_duty(pwm->hwpwm, duty);

Best regards
Uwe

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