From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH] rtc: ds1307: add trickle charger device tree binding Date: Thu, 28 Aug 2014 09:48:25 -0700 Message-ID: <20140828164825.GA12153@roeck-us.net> References: <20140828124237.GA29102@fi-ourus-dhcp00977.emea.nsn-net.net> <20140828125915.GJ14650@leverpostej> <20140828155157.GB23677@roeck-us.net> <20140828161025.GO14650@leverpostej> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20140828161025.GO14650@leverpostej> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mark Rutland Cc: Matti Vaittinen , "a.zummo-BfzFCNDTiLLj+vYz1yj4TQ@public.gmane.org" , "jason-NLaQJdtUoK4Be96aLqz0jA@public.gmane.org" , "jic23-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" , "arno-LkuqDEemtHBg9hUCZPvPmw@public.gmane.org" , "jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org" , "san-KGKi0rHxN0fKWSuBa/xFvVpr/1R2p/CL@public.gmane.org" , "hs-ynQEQJNshbs@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "rtc-linux-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org" , Sverdlin Alexander List-Id: devicetree@vger.kernel.org On Thu, Aug 28, 2014 at 05:10:25PM +0100, Mark Rutland wrote: > 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 > > > > --- > > > > .../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? > Lots ;-) http://datasheets.maximintegrated.com/en/ds/DS1307.pdf http://datasheets.maximintegrated.com/en/ds/DS1337.pdf http://datasheets.maximintegrated.com/en/ds/DS1338.pdf http://datasheets.maximintegrated.com/en/ds/DS1339.pdf http://datasheets.maximintegrated.com/en/ds/DS1340.pdf http://datasheets.maximintegrated.com/en/ds/DS1388.pdf http://datasheets.maximintegrated.com/en/ds/DS3231.pdf Code suggests that DS1339, DS1339, and DS1340 have the register. Looking into the datasheets, the configuration consists of two parts: - diode connected or not - trickle charger resistor value (250, 2000, or 4000 ohm) Given that, it seems to me that those values should be configured explicitly instead of using a binary value, and that the driver should perform the conversion from dt entry to register value. Note that the relevant bits are the lower 4 bits, not the lower 5 bits, so the above text is wrong. Guenter -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html