Re: [PATCH v2 2/3] hwmon: (pmbus) Add list_voltage to pmbus ops

[Marten Lindahl <martenli@axis.com>]

On Fri, Jun 10, 2022 at 04:16:46PM +0200, Guenter Roeck wrote:
> On 6/10/22 04:47, Mårten Lindahl wrote:
> > When checking if a regulator supports a voltage range, the regulator
> > needs to have a list_voltage callback set to the regulator_ops or else
> > -EINVAL will be returned. This support does not exist for the pmbus
> > regulators, so this patch adds pmbus_regulator_list_voltage to the
> > pmbus_regulator_ops.
> > 
> > Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
> > ---
> >   drivers/hwmon/pmbus/pmbus_core.c | 50 ++++++++++++++++++++++++++++++++
> >   1 file changed, 50 insertions(+)
> > 
> > diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> > index 478dda49a45f..24ba4b2b03d4 100644
> > --- a/drivers/hwmon/pmbus/pmbus_core.c
> > +++ b/drivers/hwmon/pmbus/pmbus_core.c
> > @@ -2711,6 +2711,55 @@ static int pmbus_regulator_set_voltage(struct regulator_dev *rdev, int min_uv,
> >   	return _pmbus_write_word_data(client, s.page, PMBUS_VOUT_COMMAND, (u16)val);
> >   }
> >   
> > +static int pmbus_regulator_list_voltage(struct regulator_dev *rdev,
> > +					 unsigned int selector)
> > +{
> > +	struct device *dev = rdev_get_dev(rdev);
> > +	struct i2c_client *client = to_i2c_client(dev->parent);
> > +	struct pmbus_data *data = i2c_get_clientdata(client);
> > +	struct pmbus_sensor s = {
> > +		.page = rdev_get_id(rdev),
> > +		.class = PSC_VOLTAGE_OUT,
> > +		.convert = true,
> > +		.data = -1,
> > +	};
> > +	int val = DIV_ROUND_CLOSEST(rdev->desc->min_uV +
> > +				    (rdev->desc->uV_step * selector),
> > +				    1000); /* convert to mV */
> > +
> > +	if (!data->vout_low[s.page]) {
> > +		if (pmbus_check_word_register(client, s.page, PMBUS_MFR_VOUT_MIN))
> > +			s.data = _pmbus_read_word_data(client, s.page, 0xff,
> > +						       PMBUS_MFR_VOUT_MIN);
> > +		if (s.data < 0) {
> > +			s.data = _pmbus_read_word_data(client, s.page, 0xff,
> > +						       PMBUS_VOUT_MARGIN_LOW);
> > +			if (s.data < 0)
> > +				return s.data;
> > +		}
> > +		data->vout_low[s.page] = pmbus_reg2data(data, &s);
> > +	}
> > +
> > +	if (!data->vout_high[s.page]) {
> > +		s.data = -1;
> > +		if (pmbus_check_word_register(client, s.page, PMBUS_MFR_VOUT_MAX))
> > +			s.data = _pmbus_read_word_data(client, s.page, 0xff,
> > +						       PMBUS_MFR_VOUT_MAX);
> > +		if (s.data < 0) {
> > +			s.data = _pmbus_read_word_data(client, s.page, 0xff,
> > +						       PMBUS_VOUT_MARGIN_HIGH);
> > +			if (s.data < 0)
> > +				return s.data;
> > +		}
> > +		data->vout_high[s.page] = pmbus_reg2data(data, &s);
> > +	}
> > +

Hi Guenter!
> 
> The code above is similar to the same code in the first patch. Please
> move it into a function (in the first patch).

Ok, I will do that. I think it will be one function for low_margin and
one for high_margin.

> 
> > +	if (val >= data->vout_low[s.page] && val <= data->vout_high[s.page])
> > +		return val * 1000; /* unit is uV */
> > +
> > +	return 0;
> 
> Other drivers return -EINVAL here. Should this be returned as well
> if rdev->desc->min_uV or rdev->desc->uV_step is 0, if selector
> is out of range, or if data->vout_low[s.page] / data->vout_high[s.page]
> is 0 ?

I will add some more checks. I will try to follow what the description
of list_voltages says in include/linux/regulator/driver.h, but it's a
bit free for interpretation, thinking of what counts as unusable
voltages :)

* @list_voltage: Return one of the supported voltages, in microvolts; zero
*	if the selector indicates a voltage that is unusable on this system;
*	or negative errno.  Selectors range from zero to one less than
*	regulator_desc.n_voltages.  Voltages may be reported in any order.

I guess, as long as a voltage is inside of the low/high margins it is a
valid voltage (even though high and/or low is 0).

Kind regards
Mårten

> 
> Thanks,
> Guenter
> 
> > +}
> > +
> >   const struct regulator_ops pmbus_regulator_ops = {
> >   	.enable = pmbus_regulator_enable,
> >   	.disable = pmbus_regulator_disable,
> > @@ -2718,6 +2767,7 @@ const struct regulator_ops pmbus_regulator_ops = {
> >   	.get_error_flags = pmbus_regulator_get_error_flags,
> >   	.get_voltage = pmbus_regulator_get_voltage,
> >   	.set_voltage = pmbus_regulator_set_voltage,
> > +	.list_voltage = pmbus_regulator_list_voltage,
> >   };
> >   EXPORT_SYMBOL_NS_GPL(pmbus_regulator_ops, PMBUS);
> >   
>