On Fri, Sep 13, 2013 at 10:13:15AM +0100, Ivan T. Ivanov wrote: > Hi Mark, > > On Thu, 2013-09-12 at 17:28 +0100, Mark Rutland wrote: > > On Thu, Aug 29, 2013 at 02:27:52PM +0100, Ivan T. Ivanov wrote: > > > From: "Ivan T. Ivanov" <iivanov@xxxxxxxxxx> > > > > > > The Qualcomm Universal Peripherial (QUP) wraps I2C mini-core and > > > provide input and output FIFO's for it. I2C controller can operate > > > as master with supported bus speeds of 100Kbps and 400Kbps. > > > > > > Signed-off-by: Ivan T. Ivanov <iivanov@xxxxxxxxxx> > > > --- > > > Documentation/devicetree/bindings/i2c/i2c-qup.txt | 99 +++++++++++++++++++++ > > > 1 file changed, 99 insertions(+) > > > create mode 100644 Documentation/devicetree/bindings/i2c/i2c-qup.txt > > > > > > diff --git a/Documentation/devicetree/bindings/i2c/i2c-qup.txt b/Documentation/devicetree/bindings/i2c/i2c-qup.txt > > > new file mode 100644 > > > index 0000000..c682726 > > > --- /dev/null > > > +++ b/Documentation/devicetree/bindings/i2c/i2c-qup.txt > > > @@ -0,0 +1,99 @@ > > > +Qualcomm Universal Periferial (QUP) I2C controller s/Periferial/Peripheral/ ? > > > + > > > +Required properties: > > > + - compatible : should be "qcom,i2c-qup" > > > + - reg : Offset and length of the register region for the device > > > + - interrupts : core interrupt > > > > How about the following: > > > > - interrupts: interrupt-specifier for the core interrupt. > > Ok. > > > > > > + > > > + - pinctrl-names: Should contain only one value - "default". > > > + - pinctrl-0: Should specify pin control group used for this controller. > > > + > > > + - clocks : phandles to clock instances of the device tree nodes > > > > Clocks aren't just phandles, they have a clock-specifier component. This > > should probably be something like: > > > > - clocks: a list of phandle + clock-specifier pairs for each entry in > > clock-names > > Right now MSM clocks [1] are just phandles, I should add #clock-cells = <0>. I see no reason to strongly tie the binding to a particular set of clocks when it's easy to make it generic. What if a new platform uses QUP, but its clocks have a number of clock-cells? As clock-specifiers may be zero cells, describing this as a phandle + clock-specifier pair means this will work with any clock provider following the common clock bindings. > > > > > > + - clock-names : > > > + "core" : Allow access to FIFO buffers and registers > > > > Huh? That description doesn't seem to descripe the hardware. > > How about: Allow access to I2C core FIFO buffers and registers. My only concern here is the words "allow access", as that seems odd in the context of a hardware description. It seems most bindings don't describe what the clocks do as that's defined in the manual for a piece of hardware anyway, so unfortunately I don't have a good example. I think something like the below would be more in keeping with what's expected: "core": Clock controlling the FIFO buffers and registers > > > > > > + "iface" : Clock used by QUP interface > > > > Which interface? The slave interface the CPUs access, or the interface > > to the I2C devices? > > > My understanding for this is that QUP is wrapping I2C core. QUP is > interface to I2C core. Ok. > > > > > Are these the only clock inputs to the device? > > Yep. Ok. > > > > > Is there a regulator input that might need to be specified? > > > > No. Power management is done via clock gating. Ok. > > > > + > > > + - #address-cells : should be <1> Address cells for I2C device address > > > + - #size-cells : should be <0> I2C addresses have no size component. > > > + > > > +Optional properties : > > > + - Child nodes conforming to i2c bus binding > > > + - clock-frequency : Desired I2C bus clock frequency in Hz. If > > > + not set thedefault frequency is 100kHz > > > > Why is this necessary? > > This is how I2C bus frequency could be specified. It is standard > I2C property. Not sure that I get the question. Not all i2c bindings have this, but I see many do. Never mind. > > > > > > + - qcom,src-freq : Frequency of the source clocking this bus in Hz. > > > + Divider value is set based on soruce-frequency and > > > + desired I2C bus frequency. If this value is not > > > + provided, the source clock is assumed to be running > > > + at 19.2 MHz. > > > > This looks like it should be a clock input. > > Thanks, I will change it. Great! Cheers, Mark. -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
