Re: [PATCH] rtc: ds1307: add trickle charger device tree binding

Mark Rutland
2014-08-28T16:11:14Z

On Thu, Aug 28, 2014 at 04:51:57PM +0100, Guenter Roeck wrote:
> On Thu, Aug 28, 2014 at 01:59:15PM +0100, Mark Rutland wrote:
> > On Thu, Aug 28, 2014 at 01:42:44PM +0100, Matti Vaittinen wrote:
> > > Patch adding support for specifying trickle charger setup from device
> > > tree. Patch is based on linux-next tree.
> > >
> > >
> > > Some DS13XX devices have "trickle chargers". Introduce a device tree binding
> > > for specifying the setup and register values.
> > >
> > > Signed-off-by: Matti Vaittinen <matti.vaittinen@nsn.com>
> > > ---
> > > .../devicetree/bindings/i2c/trivial-devices.txt | 1 -
> > > .../devicetree/bindings/rtc/dallas,ds1339.txt | 19 ++++++++++
> > > drivers/rtc/rtc-ds1307.c | 44 ++++++++++++++++++++--
> > > 3 files changed, 59 insertions(+), 5 deletions(-)
> > > create mode 100644 Documentation/devicetree/bindings/rtc/dallas,ds1339.txt
> > >
> > > diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
> > > index 6af570e..e9206a4 100644
> > > --- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt
> > > +++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
> > > @@ -35,7 +35,6 @@ catalyst,24c32 i2c serial eeprom
> > > cirrus,cs42l51 Cirrus Logic CS42L51 audio codec
> > > dallas,ds1307 64 x 8, Serial, I2C Real-Time Clock
> > > dallas,ds1338 I2C RTC with 56-Byte NV RAM
> > > -dallas,ds1339 I2C Serial Real-Time Clock
> > > dallas,ds1340 I2C RTC with Trickle Charger
> > > dallas,ds1374 I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output
> > > dallas,ds1631 High-Precision Digital Thermometer
> > > diff --git a/Documentation/devicetree/bindings/rtc/dallas,ds1339.txt b/Documentation/devicetree/bindings/rtc/dallas,ds1339.txt
> > > new file mode 100644
> > > index 0000000..9faf40e
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/rtc/dallas,ds1339.txt
> > > @@ -0,0 +1,19 @@
> > > +* Dallas DS1339 I2C Serial Real-Time Clock
> > > +
> > > +Required properties:
> > > +- compatible: Should contain "dallas,ds1339".
> > > +- reg: I2C address for chip
> > > +
> > > +Optional properties:
> > > +- trickle_setup : Used Trickle Charger configuration,
> > > + corresponding to 5 lowest bits in trickle charger register.
> >
> The value is provided via platform data, so it is platform specific
> and presumably needs to be configurable. I did, however, not find
> a single in-kernel driver which is actually setting it.
> So this is a good question.

I'm uncomfortable adding a field we don't understand to DT.

Is there any publicly-available documentation for the device?

> > s/_/-/ in property names please.
> >
> > What do these bits do? is there any documentation available?
> >
> > Why do they need to be in the DT?
> >
> > Why do we not have a higher-level description?
> >
> > > +- trickle_reg : Trickle charger register address. Defaults to 0x10 for ds1339.
> >
> > Is this expected to change? Why does this need to be in the DT?
> >
> A quick look into the code suggests that this is a chip specific register,
> and the register address is set by the driver depending on the chip type.
> I don't think it should be configurable via dt.

Ok.

Cheers,
Mark.