Re: [PATCH 13/14] regulator: pwm: Support extra continuous mode cases

[Brian Norris <briannorris@chromium.org>]

Hi Boris,

On Fri, Jun 03, 2016 at 10:23:11AM +0200, Boris Brezillon wrote:
> The continuous mode allows one to declare a PWM regulator without having
> to declare the voltage <-> dutycycle association table. It works fine as
> long as your voltage(dutycycle) function is linear, but also has the
> following constraints:
> 
> - dutycycle for min_uV = 0%
> - dutycycle for max_uV = 100%
> - dutycycle for min_uV < dutycycle for max_uV
> 
> While the linearity constraint is acceptable for now, we sometimes need to
> restrict of the PWM range (to limit the maximum/minimum voltage for
> example) or have a min_uV_dutycycle > max_uV_dutycycle (this could be
> tweaked with PWM polarity, but not all PWMs support inverted polarity).
> 
> Add the pwm-dutycycle-range and pwm-dutycycle-unit DT properties to define
> such constraints. If those properties are not defined, the PWM regulator
> use the default pwm-dutycycle-range = <0 100> and
> pwm-dutycycle-unit = <100> values (existing behavior).
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> ---
>  drivers/regulator/pwm-regulator.c | 80 ++++++++++++++++++++++++++++++++++-----
>  1 file changed, 71 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/regulator/pwm-regulator.c b/drivers/regulator/pwm-regulator.c
> index c39ecd1..2e70eb1 100644
> --- a/drivers/regulator/pwm-regulator.c
> +++ b/drivers/regulator/pwm-regulator.c

...

> @@ -132,31 +141,67 @@ static int pwm_regulator_is_enabled(struct regulator_dev *dev)
>  static int pwm_regulator_get_voltage(struct regulator_dev *rdev)
>  {
>  	struct pwm_regulator_data *drvdata = rdev_get_drvdata(rdev);
> +	unsigned int min_uV_duty = drvdata->continuous.min_uV_dutycycle;
> +	unsigned int max_uV_duty = drvdata->continuous.max_uV_dutycycle;
> +	unsigned int duty_unit = drvdata->continuous.dutycycle_unit;
>  	int min_uV = rdev->constraints->min_uV;
> -	int diff = rdev->constraints->max_uV - min_uV;
> +	int max_uV = rdev->constraints->max_uV;
> +	int diff_uV = max_uV - min_uV;
>  	struct pwm_state pstate;
> +	unsigned int diff_duty;
> +	unsigned int voltage;
>  
>  	pwm_get_state(drvdata->pwm, &pstate);
>  
> -	return min_uV + pwm_get_relative_duty_cycle(&pstate, diff);
> +	voltage = pwm_get_relative_duty_cycle(&pstate, duty_unit);
> +
> +	if (max_uV_duty < min_uV_duty) {

I still might have appreciated a comment above this line (and similar
in set_voltage()) to help explain why max can be less than min -- you
have it in the commit message, but nowhere in the code. Not a big deal,
and the code looks otherwise good:

Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>


> +		voltage = min_uV_duty - voltage;
> +		diff_duty = min_uV_duty - max_uV_duty;
> +	} else {
> +		voltage = voltage - min_uV_duty;
> +		diff_duty = max_uV_duty - min_uV_duty;
> +	}
> +
> +	voltage = DIV_ROUND_CLOSEST_ULL((u64)voltage * diff_uV, diff_duty);
> +
> +	return voltage + min_uV;
>  }
>  
>  static int pwm_regulator_set_voltage(struct regulator_dev *rdev,
> -					int min_uV, int max_uV,
> -					unsigned *selector)
> +				     int req_min_uV, int req_max_uV,
> +				     unsigned int *selector)
>  {
>  	struct pwm_regulator_data *drvdata = rdev_get_drvdata(rdev);
> +	unsigned int min_uV_duty = drvdata->continuous.min_uV_dutycycle;
> +	unsigned int max_uV_duty = drvdata->continuous.max_uV_dutycycle;
> +	unsigned int duty_unit = drvdata->continuous.dutycycle_unit;
>  	unsigned int ramp_delay = rdev->constraints->ramp_delay;
> -	unsigned int req_diff = min_uV - rdev->constraints->min_uV;
> +	int min_uV = rdev->constraints->min_uV;
> +	int max_uV = rdev->constraints->max_uV;
> +	int diff_uV = max_uV - min_uV;
>  	struct pwm_state pstate;
> -	unsigned int diff;
> +	unsigned int diff_duty;
> +	unsigned int dutycycle;
>  	int ret;
>  
>  	pwm_prepare_new_state(drvdata->pwm, &pstate);
> -	diff = rdev->constraints->max_uV - rdev->constraints->min_uV;
>  
> -	/* We pass diff as the scale to get a uV precision. */
> -	pwm_set_relative_duty_cycle(&pstate, req_diff, diff);
> +	if (max_uV_duty < min_uV_duty)
> +		diff_duty = min_uV_duty - max_uV_duty;
> +	else
> +		diff_duty = max_uV_duty - min_uV_duty;
> +
> +	dutycycle = DIV_ROUND_CLOSEST_ULL((u64)(req_min_uV - min_uV) *
> +					  diff_duty,
> +					  diff_uV);
> +
> +	if (max_uV_duty < min_uV_duty)
> +		dutycycle = min_uV_duty - dutycycle;
> +	else
> +		dutycycle = min_uV_duty + dutycycle;
> +
> +	pwm_set_relative_duty_cycle(&pstate, dutycycle, duty_unit);
>  
>  	ret = pwm_apply_state(drvdata->pwm, &pstate);
>  	if (ret) {

[...]

Brian