[RFC Patch 1/4] mfd: AXP20x: Add power supply bindings documentation

Bruno Prémont
2014-11-03T20:02:44Z

Hi Maxime,

On Tue, 21 October 2014 Maxime Ripard <maxime.ripard@free-electrons.com> wrote:
> On Tue, Oct 21, 2014 at 06:09:16PM +0200, Bruno Pr?mont wrote:
> > On Tue, 21 October 2014 Lee Jones <lee.jones@linaro.org> wrote:
> > > On Mon, 20 Oct 2014, Bruno Pr?mont wrote:
> > > > ---
> > > > Note: the OCV values seem to have some defaults build into the
> > > > PMIC though may need adjustment if the used battery has a different
> > > > open circuit voltage curve.
> > > > As far as understood (these values are set in vendor driver but not
> > > > mentioned in chip documentation) they represent charge percentage
> > > > for some predefined voltages.
> > > >
> > > > If prefixing these values with "x-power," is preferred the following
> > > > patch should becomes a dependency:
> > > > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-June/267606.html
> > > > and users in patch 2/4, 4/4 need adjusting.
> > > >
> > > >
> > > > Documentation/devicetree/bindings/mfd/axp20x.txt | 20 +
> > > > 1 files changed, 20 insertions(+), 0 deletion(-)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/mfd/axp20x.txt b/Documentation/devicetree/bindings/mfd/axp20x.txt
> > > > index cc9e01b..8ea681c 100644
> > > > --- a/Documentation/devicetree/bindings/mfd/axp20x.txt
> > > > +++ b/Documentation/devicetree/bindings/mfd/axp20x.txt
> > > > @@ -28,6 +28,20 @@ Required properties:
> > > > (range: 750-1875). Default: 1.5MHz
> > > >
> > > > Optional properties for DCDCs:
> > > > +- backup: Settings for backup/RTC battery charger
> > > > + (Voltage in ?V, current in ?A)
> > > > + If not present, charger will be left untouched
> > > > +- battery.ocv: OCV capacity curve points (16 data values)
> > > > +- battery.resistance: internal battery resistance in m?
> > > > + (defaults to 100m?)
> > > > +- battery.capacity: Battery capacity in mAh
> > > > + If this attribute is missing, charger will be disabled
> > > > + unless there is a battery connected.
> > > > +- battery.temp_sensor: Description of temperautre sensor, 3 values
> > > > + - driver current (20?A, 40?A, 60?A or 80?A)
> > > > + - low temperature warning level (in ?V)
> > > > + - high temperature warning level (in ?V)
> > > > + If missing, temperature sensor gets disabled
> > > > - x-powers,dcdc-workmode: 1 for PWM mode, 0 for AUTO mode
> > > > Default: AUTO mode
> > > >
> > > > @@ -49,6 +63,12 @@ axp209: pmic at 34 {
> > > > ldo3in-supply = <&axp_ipsout_reg>;
> > > > ldo5in-supply = <&axp_ipsout_reg>;
> > > >
> > > > + backup = <3000000 200>;
> > > > + battery.ocv = <0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0>;
> > > > + battery.resistance = <0>;
> > > > + battery.capacity = <2000>;
> > > > + battery.temp_sensor = <20 1000000 4000000>;
> > >
> > > Since when do we use '.'s in property names?
> >
> > I've not found guidelines on this, but whatever is the right way to
> > name them, I'm open for suggestions.
>
> You can take a look at the ePAPR specs. Even if it's quite outdated,
> it still puts you in the right mindset.

There seems to be some kind of e-mail wall in front of this document.

> That being said, since they are driver-specific properties, they
> should be prefixed by the vendor name (here x-powers).
>
> And I think they all belong in a sub-node, just like what's been done
> for the regulators.

Doing something like this?:

--- a/arch/arm/boot/dts/sun7i-a20-cubietruck.dts
+++ b/arch/arm/boot/dts/sun7i-a20-cubietruck.dts
@@ -126,9 +126,11 @@
interrupt-controller;
#interrupt-cells = <1>;

- backup = <3000000 200>;
- battery.resistance = <100>;
- battery.capacity = <2000>;
+ x-powers,backup = <3000000 200>;
+ battery: battery at 0 {
+ x-powers,resistance = <100>;
+ x-powers,capacity = <2000>;
+ };
};
};

What are the rules to define the label after the colon?
Looking at the existing nodes it's either some address or a number...

and then the following in driver code (also adjusting the other
property names accessed)?:

@@ -678,11 +677,11 @@ static int axp20x_battery_config(struct platform_device *pdev,
if (ret)
return ret;

- np = of_node_get(axp20x->dev->of_node);
+ np = of_find_node_by_name(axp20x->dev->of_node, "battery");
if (!np)
return -ENODEV;

- ret = of_property_read_u32_array(np, "battery.ocv", ocv, 16);
+ ret = of_property_read_u32_array(np, "x-powers,ocv", ocv, 16);
for (i = 0; ret == 0 && i < ARRAY_SIZE(ocv); i++)
if (ocv[i] > 100) {
dev_warn(&pdev->dev, "OCV[%d] %u > 100\n", i, ocv[i]);

Bruno