On Tue, Oct 09, 2018 at 11:51:22AM -0700, Atish Patra wrote: > From: "Wesley W. Terpstra" <[email protected]> > > DT documentation for PWM controller added with updated compatible > string. > > Signed-off-by: Wesley W. Terpstra <[email protected]> > [Atish: Compatible string update] > Signed-off-by: Atish Patra <[email protected]> > --- > .../devicetree/bindings/pwm/pwm-sifive.txt | 32 > ++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > create mode 100644 Documentation/devicetree/bindings/pwm/pwm-sifive.txt > > diff --git a/Documentation/devicetree/bindings/pwm/pwm-sifive.txt > b/Documentation/devicetree/bindings/pwm/pwm-sifive.txt > new file mode 100644 > index 00000000..532b10fc > --- /dev/null > +++ b/Documentation/devicetree/bindings/pwm/pwm-sifive.txt > @@ -0,0 +1,32 @@ > +SiFive PWM controller > + > +Unlike most other PWM controllers, the SiFive PWM controller currently only > +supports one period for all channels in the PWM. This is set globally in DTS. > +The period also has significant restrictions on the values it can achieve, > +which the driver rounds to the nearest achievable frequency.
What restrictions are these? If "nearest achievable" is too far off the target period it might be preferable to error out. > +Required properties: > +- compatible: should be one of > + "sifive,fu540-c000-pwm0","sifive,pwm0". What's the '0' in here? A version number? > + PWM controller is HiFive Unleashed specific chip which warrants a > + specific compatible string. The second string is kept for backward > + compatibility until a firmware update with latest compatible string. > +- reg: physical base address and length of the controller's registers > +- clocks: The frequency the controller runs at > +- #pwm-cells: Should be 2. > + The first cell is the PWM channel number > + The second cell is the PWM polarity > +- sifive,approx-period: the driver will get as close to this period as it can Given the above comment, maybe "sifive,period"? Thierry
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