linux-kernel - Re: [PATCH v4 2/2] hwmon: pmbus: max20730: adjust the vout reading given voltage divider

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Date:   Sun, 4 Oct 2020 20:07:36 -0700
From:   Chu Lin <linchuyuan@...gle.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     jdelvare@...e.com, robh+dt@...nel.org, linux-hwmon@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] hwmon: pmbus: max20730: adjust the vout reading
 given voltage divider

On Sun, Oct 4, 2020 at 8:43 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On Sun, Oct 04, 2020 at 03:14:45AM +0000, Chu Lin wrote:
> > Problem:
> > We use voltage dividers so that the voltage presented at the voltage
> > sense pins is confusing. We might need to convert these readings to more
> > meaningful readings given the voltage divider.
> >
> > Solution:
> > Read the voltage divider resistance from dts and convert the voltage
> > reading to a more meaningful reading.
> >
> > Testing:
> > max20730 with voltage divider
> >
> > Signed-off-by: Chu Lin <linchuyuan@...gle.com>
> > ---
> > ChangeLog v1 -> v2
> >   hwmon: pmbus: max20730:
> >   - Don't do anything to the ret if an error is returned from pmbus_read_word
> >   - avoid overflow when doing multiplication
> >
> > ChangeLog v2 -> v3
> >   dt-bindings: hwmon: max20730:
> >   - Provide the binding documentation in yaml format
> >   hwmon: pmbus: max20730:
> >   - No change
> >
> > ChangeLog v3 -> v4
> >   dt-bindings: hwmon: max20730:
> >   - Fix highefficiency to high efficiency in description
> >   - Fix presents to present in vout-voltage-divider
> >   - Add additionalProperties: false
> >   hwmon: pmbus: max20730:
> >   - No change
>
> You claim that there have been no changes since v2 of this patch,
> yet you dropped my Reviewed-by: tag. Any reason ?
>
> Guenter
Sorry for the confusion. I thought I can't tag the patch with the Review-by tag.
Just to make sure I do correctly next time, once you tagged a certain
patch in the batch
If there is no change from version to version for this patch, I should
carry the tags when
submitting new revisions. Also, please let me know what is the best
way to fix this revision?
Should I submit a new V5 with the tag attached?

Sincerely,
Chu

>
> >
> >  drivers/hwmon/pmbus/max20730.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >
> > diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c
> > index a151a2b588a5..fbf2f1e6c969 100644
> > --- a/drivers/hwmon/pmbus/max20730.c
> > +++ b/drivers/hwmon/pmbus/max20730.c
> > @@ -31,6 +31,7 @@ struct max20730_data {
> >       struct pmbus_driver_info info;
> >       struct mutex lock;      /* Used to protect against parallel writes */
> >       u16 mfr_devset1;
> > +     u32 vout_voltage_divider[2];
> >  };
> >
> >  #define to_max20730_data(x)  container_of(x, struct max20730_data, info)
> > @@ -114,6 +115,14 @@ static int max20730_read_word_data(struct i2c_client *client, int page,
> >               max_c = max_current[data->id][(data->mfr_devset1 >> 5) & 0x3];
> >               ret = val_to_direct(max_c, PSC_CURRENT_OUT, info);
> >               break;
> > +     case PMBUS_READ_VOUT:
> > +             ret = pmbus_read_word_data(client, page, phase, reg);
> > +             if (ret > 0 && data->vout_voltage_divider[0] && data->vout_voltage_divider[1]) {
> > +                     u64 temp = DIV_ROUND_CLOSEST_ULL((u64)ret * data->vout_voltage_divider[1],
> > +                                                      data->vout_voltage_divider[0]);
> > +                     ret = clamp_val(temp, 0, 0xffff);
> > +             }
> > +             break;
> >       default:
> >               ret = -ENODATA;
> >               break;
> > @@ -364,6 +373,15 @@ static int max20730_probe(struct i2c_client *client,
> >       data->id = chip_id;
> >       mutex_init(&data->lock);
> >       memcpy(&data->info, &max20730_info[chip_id], sizeof(data->info));
> > +     if (of_property_read_u32_array(client->dev.of_node, "vout-voltage-divider",
> > +                                    data->vout_voltage_divider,
> > +                                    ARRAY_SIZE(data->vout_voltage_divider)) != 0)
> > +             memset(data->vout_voltage_divider, 0, sizeof(data->vout_voltage_divider));
> > +     if (data->vout_voltage_divider[1] < data->vout_voltage_divider[0]) {
> > +             dev_err(dev,
> > +                     "The total resistance of voltage divider is less than output resistance\n");
> > +             return -ENODEV;
> > +     }
> >
> >       ret = i2c_smbus_read_word_data(client, MAX20730_MFR_DEVSET1);
> >       if (ret < 0)
> > --
> > 2.28.0.806.g8561365e88-goog
> >