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

Brian Norris
2016-06-03T21:03:08Z

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