Re: [RFC 1/4] pwm: sifive: Add DT documentation for SiFive PWM Controller.
From: Thierry Reding <hidden>
Date: 2018-10-10 13:49:32
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linux-gpio, linux-pwm, linux-riscv, lkml
On Tue, Oct 09, 2018 at 11:51:22AM -0700, Atish Patra wrote:
quoted hunk ↗ jump to hunk
From: "Wesley W. Terpstra" <redacted> DT documentation for PWM controller added with updated compatible string. Signed-off-by: Wesley W. Terpstra <redacted> [Atish: Compatible string update] Signed-off-by: Atish Patra <redacted> --- .../devicetree/bindings/pwm/pwm-sifive.txt | 32 ++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 Documentation/devicetree/bindings/pwm/pwm-sifive.txtdiff --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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