Hello Miquel,
On Sun, May 03, 2020 at 12:54:53PM +0200, Miquel Raynal wrote:
> +static u8 max7313_pwm_get_intensity(struct pca953x_chip *pca_chip,
> + unsigned int idx)
> +{
> + struct device *dev = &pca_chip->client->dev;
> + unsigned int reg, shift, val, output;
> + u8 intensity;
> + bool phase;
> + int ret;
> +
> + /* Retrieve the intensity */
> + reg = MAX7313_INTENSITY + (idx / PWM_PER_REG);
> + shift = (idx % PWM_PER_REG) ? PWM_BITS_PER_REG : 0;
I would find
shift = (idx % PWM_PER_REG) * PWM_BITS_PER_REG
more natural here as your formula only works for PWM_PER_REG = 2.
> + mutex_lock(&pca_chip->i2c_lock);
> + ret = regmap_read(pca_chip->regmap, reg, &val);
> + mutex_unlock(&pca_chip->i2c_lock);
> + if (ret < 0) {
> + dev_err(dev, "Cannot retrieve PWM intensity (%d)\n", ret);
Please use %pe for error codes.
> + return 0;
> + }
> +
> + val >>= shift;
> + val &= PWM_INTENSITY_MASK;
> +
> + /* Retrieve the phase */
> + reg = pca953x_recalc_addr(pca_chip, pca_chip->regs->output, idx, 0, 0);
> +
> + mutex_lock(&pca_chip->i2c_lock);
> + ret = regmap_read(pca_chip->regmap, reg, &output);
> + mutex_unlock(&pca_chip->i2c_lock);
> + if (ret < 0) {
> + dev_err(dev, "Cannot retrieve PWM phase (%d)\n", ret);
> + return 0;
> + }
> +
> + phase = output & BIT(idx % BANK_SZ);
Would it make sense to cache the phase value to reduce register access
and locking here?
> [...]
> +static int max7313_pwm_apply(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + const struct pwm_state *state)
> +{
> + struct max7313_pwm *max_pwm = to_max7313_pwm(chip);
> + struct pca953x_chip *pca_chip = to_pca953x(max_pwm);
> + unsigned int intensity, active;
> + int ret = 0;
> +
> + if (!state->enabled ||
> + state->period < PWM_PERIOD_NS ||
> + state->polarity != PWM_POLARITY_NORMAL)
> + return -EINVAL;
You could simulate state->enabled = false using duty_cycle = 0.
> + /* Convert the duty-cycle to be in the [0;16] range */
> + intensity = max7313_pwm_duty_to_intensity(state->duty_cycle);
This might return a value > 16 if state->duty_cycle > PWM_PERIOD_NS.
I suggest to do
duty_cycle = min(state->duty_cycle, PWM_PERIOD_NS);
and use that value instead of state->duty_cycle.
> + /*
> + * The hardware is supposedly glitch-free when changing the intensity,
> + * unless we need to flip the blink phase to reach an extremity or the
> + * other of the spectrum (0/16 from phase 1, 16/16 from phase 0).
s/other of/other end of/. I don't understand the difference between
extremity and "other end of the spectrum".
> + */
> + return max7313_pwm_set_state(pca_chip, pwm, intensity);
> +}
> +
> +static void max7313_pwm_get_state(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + struct pwm_state *state)
> +{
> + struct max7313_pwm *max_pwm = to_max7313_pwm(chip);
> + struct pca953x_chip *pca_chip = to_pca953x(max_pwm);
> + u8 intensity;
> +
> + state->enabled = true;
> + state->period = PWM_PERIOD_NS;
> + state->polarity = PWM_POLARITY_NORMAL;
> +
> + intensity = max7313_pwm_get_intensity(pca_chip, pwm->hwpwm);
> + state->duty_cycle = max7313_pwm_intensity_to_duty(intensity);
Please round up the division in max7313_pwm_intensity_to_duty().
(The reasoning is: with rounding down the following can happen:
/* this configures for 15/16 */
pwm_apply_state(pwm, { .duty_cycle = 31249, .period = 31250 });
/* assume this called your .get_state callback */
pwm_get_state(pwm, &state);
/*
* we now have
* state.duty_cycle = 29296;
* state.period = 31250;
* right?
*/
/* this configures for 14/16 because 29296 * 16 / 31250 < 15 */
pwm_apply_state(pwm, &state);
But I want this to be idempotent, i.e. pwm_get_state has to round up and
then return .duty_cycle = 29297 in the above example which is enough to
let .apply_state() configure 15/16 again. Enabling PWM_DEBUG should
catch this.)
> +};
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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