Re: [PATCH v4 4/7] pwm: Add support for Azoteq IQS620A PWM generator

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On Fri, Jan 17, 2020 at 02:35:57AM +0000, Jeff LaBundy wrote:
> +static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> +				 struct pwm_state *state)
> +{
> +	struct iqs620_pwm_private *iqs620_pwm;
> +
> +	iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
> +
> +	mutex_lock(&iqs620_pwm->lock);
> +
> +	/*
> +	 * Since the device cannot generate a 0% duty cycle, requests to do so
> +	 * cause subsequent calls to iqs620_pwm_get_state to report the output
> +	 * as disabled with duty cycle equal to that which was in use prior to
> +	 * the request. This is not ideal, but is the best compromise based on
> +	 * the capabilities of the device.
> +	 */
> +	state->enabled = iqs620_pwm->out_en;

Hmm, when .get_state is called first (before the first invokation of
.apply) .out_en doesn't represent the hardware's state but is false
unconditionally. This makes it hard to take over a running PWM setup by
the bootloader.

Best regards
Uwe

> +	state->duty_cycle = DIV_ROUND_UP((iqs620_pwm->duty_val + 1) *
> +					 IQS620_PWM_PERIOD_NS, 256);
> +
> +	mutex_unlock(&iqs620_pwm->lock);
> +
> +	state->period = IQS620_PWM_PERIOD_NS;
> +}

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |



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