On Mon, Oct 06, 2014 at 12:33:26PM +0100, Mark Rutland wrote: > On Mon, Oct 06, 2014 at 11:13:51AM +0100, Thierry Reding wrote: > > On Wed, Oct 01, 2014 at 04:53:01PM +0200, Boris Brezillon wrote: > > > From: Boris BREZILLON <boris.brezillon@xxxxxxxxxxxxxxxxxx> > > > > > > The HLCDC IP available in some Atmel SoCs (i.e. sam9x5i.e. at91sam9n12, > > > at91sam9x5 family or sama5d3 family) provide a PWM device. > > > > > > The DT bindings used for this PWM device is following the default 3 cells > > > bindings described in Documentation/devicetree/bindings/pwm/pwm.txt. > > > > > > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> > > > --- > > > .../devicetree/bindings/pwm/atmel-hlcdc-pwm.txt | 55 ++++++++++++++++++++++ > > > 1 file changed, 55 insertions(+) > > > create mode 100644 Documentation/devicetree/bindings/pwm/atmel-hlcdc-pwm.txt > > > > > > diff --git a/Documentation/devicetree/bindings/pwm/atmel-hlcdc-pwm.txt b/Documentation/devicetree/bindings/pwm/atmel-hlcdc-pwm.txt > > > new file mode 100644 > > > index 0000000..86ad3e2 > > > --- /dev/null > > > +++ b/Documentation/devicetree/bindings/pwm/atmel-hlcdc-pwm.txt > > > @@ -0,0 +1,55 @@ > > > +Device-Tree bindings for Atmel's HLCDC (High LCD Controller) PWM driver > > > + > > > +The Atmel HLCDC PWM is subdevice of the HLCDC MFD device. > > > +See ../mfd/atmel-hlcdc.txt for more details. > > > + > > > +Required properties: > > > + - compatible: value should be one of the following: > > > + "atmel,hlcdc-pwm" > > > + - pinctr-names: the pin control state names. Should contain "default". > > > + - pinctrl-0: should contain the pinctrl states described by pinctrl > > > + default. > > > + - #pwm-cells: should be set to 3. This PWM chip use the default 3 cells > > > + bindings defined in Documentation/devicetree/bindings/pwm/pwm.txt. > > > + The first cell encodes the PWM id (0 is the only acceptable value here, > > > + because the chip only provide one PWM). > > > + The second cell encodes the PWM period in nanoseconds. > > > + The third cell encodes the PWM flags (the only supported flag is > > > + PWM_POLARITY_INVERTED) > > > > Given that this already refers to the default 3 cells binding it doesn't > > need to repeat part of the contents of pwm.txt. > > Given that pwm.txt states: > > pwm-specifier : array of #pwm-cells specifying the given PWM > (controller specific) It also goes on to say that: " pwm-specifier typically encodes the chip-relative PWM number and the PWM period in nanoseconds. Optionally, the pwm-specifier can encode a number of flags (defined in <dt-bindings/pwm/pwm.h>) in a third cell: - PWM_POLARITY_INVERTED: invert the PWM signal polarity " > I'd leave it here. Just because pwm.txt gives an example of a controller > specific meaning for the pwm cells, I don't think we should rely on it > everywhere. If we do have a default meaning for a specifier and the majority (in case of PWM every single one) of the device-specific bindings use it, then I don't think it makes sense to duplicate information everywhere else. We've been doing the same thing across the kernel for a long time now, why should PWM be special? Thierry
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