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

Boris Brezillon
2016-06-04T06:30:09Z

On Fri, 3 Jun 2016 14:03:08 -0700
Brian Norris <briannorris@chromium.org> wrote:

> 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:

Sure, I'll add more comments in the next version.

Thanks,

Boris

>
> 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

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering