RE: [PATCH v1 3/3] dt-bindings: riscv: convert pwm bindings to json-schema

[Sagar Kadam <sagar.kadam@openfive.com>]

Hello Rob,

> -----Original Message-----
> From: Rob Herring <robh@kernel.org>
> Sent: Wednesday, September 23, 2020 2:07 AM
> To: Sagar Kadam <sagar.kadam@openfive.com>
> Cc: linux-pwm@vger.kernel.org; linux-kernel@vger.kernel.org; linux-
> riscv@lists.infradead.org; devicetree@vger.kernel.org; linux-
> clk@vger.kernel.org; mturquette@baylibre.com; sboyd@kernel.org; Paul
> Walmsley ( Sifive) <paul.walmsley@sifive.com>; palmer@dabbelt.com;
> tglx@linutronix.de; jason@lakedaemon.net; maz@kernel.org;
> thierry.reding@gmail.com; u.kleine-koenig@pengutronix.de;
> lee.jones@linaro.org; aou@eecs.berkeley.edu; Yash Shah
> <yash.shah@openfive.com>
> Subject: Re: [PATCH v1 3/3] dt-bindings: riscv: convert pwm bindings to json-
> schema
> 
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> 
> On Thu, Sep 10, 2020 at 04:14:04PM +0530, Sagar Kadam wrote:
> > Convert device tree bindings for SiFive's PWM controller to YAML
> > format.
> >
> > Signed-off-by: Sagar Kadam <sagar.kadam@sifive.com>
> > ---
> >  .../devicetree/bindings/pwm/pwm-sifive.txt         | 33 ----------
> >  .../devicetree/bindings/pwm/pwm-sifive.yaml        | 72
> ++++++++++++++++++++++
> >  2 files changed, 72 insertions(+), 33 deletions(-)  delete mode
> > 100644 Documentation/devicetree/bindings/pwm/pwm-sifive.txt
> >  create mode 100644
> > Documentation/devicetree/bindings/pwm/pwm-sifive.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/pwm/pwm-sifive.txt
> > b/Documentation/devicetree/bindings/pwm/pwm-sifive.txt
> > deleted file mode 100644
> > index 3d1dd7b0..0000000
> > --- a/Documentation/devicetree/bindings/pwm/pwm-sifive.txt
> > +++ /dev/null
> > @@ -1,33 +0,0 @@
> > -SiFive PWM controller
> > -
> > -Unlike most other PWM controllers, the SiFive PWM controller
> > currently only -supports one period for all channels in the PWM. All
> > PWMs need to run at -the same period. The period also has significant
> > restrictions on the values -it can achieve, which the driver rounds to the
> nearest achievable period.
> > -PWM RTL that corresponds to the IP block version numbers can be found
> > -here:
> > -
> > -https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/de
> > vices/pwm
> > -
> > -Required properties:
> > -- compatible: Should be "sifive,<chip>-pwm" and "sifive,pwm<version>".
> > -  Supported compatible strings are: "sifive,fu540-c000-pwm" for the
> > SiFive
> > -  PWM v0 as integrated onto the SiFive FU540 chip, and "sifive,pwm0"
> > for the
> > -  SiFive PWM v0 IP block with no chip integration tweaks.
> > -  Please refer to sifive-blocks-ip-versioning.txt for details.
> > -- reg: physical base address and length of the controller's registers
> > -- clocks: Should contain a clock identifier for the PWM's parent clock.
> > -- #pwm-cells: Should be 3. See pwm.yaml in this directory
> > -  for a description of the cell format.
> > -- interrupts: one interrupt per PWM channel
> > -
> > -Examples:
> > -
> > -pwm:  pwm@10020000 {
> > -     compatible = "sifive,fu540-c000-pwm", "sifive,pwm0";
> > -     reg = <0x0 0x10020000 0x0 0x1000>;
> > -     clocks = <&tlclk>;
> > -     interrupt-parent = <&plic>;
> > -     interrupts = <42 43 44 45>;
> > -     #pwm-cells = <3>;
> > -};
> > diff --git a/Documentation/devicetree/bindings/pwm/pwm-sifive.yaml
> > b/Documentation/devicetree/bindings/pwm/pwm-sifive.yaml
> > new file mode 100644
> > index 0000000..415d053
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/pwm/pwm-sifive.yaml
> > @@ -0,0 +1,72 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) # Copyright
> > +(C) 2020 SiFive, Inc.
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/pwm/pwm-sifive.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: SiFive PWM controller
> > +
> > +maintainers:
> > +  - Yash Shah <yash.shah@sifive.com>
> > +  - Sagar Kadam <sagar.kadam@sifive.com>
> > +  - Paul Walmsley <paul.walmsley@sifive.com>
> > +
> > +description:
> > +  Unlike most other PWM controllers, the SiFive PWM controller
> > +currently
> > +  only supports one period for all channels in the PWM. All PWMs need
> > +to
> > +  run at the same period. The period also has significant
> > +restrictions on
> > +  the values it can achieve, which the driver rounds to the nearest
> > +  achievable period. PWM RTL that corresponds to the IP block version
> > +  numbers can be found here -
> > +
> > +
> > + https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/d
> > + evices/pwm
> > +
> > +properties:
> > +  compatible:
> > +    items:
> > +      - const: sifive,fu540-c000-pwm
> > +      - const: sifive,pwm0
> > +    description:
> > +      Should be "sifive,<chip>-pwm" and "sifive,pwm<version>". Supported
> > +      compatible strings are "sifive,fu540-c000-pwm" for the SiFive PWM v0
> > +      as integrated onto the SiFive FU540 chip, and "sifive,pwm0" for the
> > +      SiFive PWM v0 IP block with no chip integration tweaks.
> > +      Please refer to sifive-blocks-ip-versioning.txt for details.
> > +
> > +  reg:
> > +    maxItems: 1
> > +    description: Physical base address and length of the controller's
> > + registers
> 
> Drop description.
Okay.
> 
> > +
> > +  clocks:
> > +    description: Should contain a clock identifier for the PWM's parent
> clock.
> 
> How many clocks?
> 
PWM IP block instance is clocked with single clock (tlclk).
> > +
> > +  "#pwm-cells":
> > +    const: 3
> > +    description:
> > +      Should be 3. See pwm.yaml in this directory for a description of the
> > +      cell format.
> 
> Drop.
Okay, I will drop this description.
> 
> > +
> > +  interrupts:
> > +    maxItems: 1
> 
> Is it 1 or...
> 
> > +    description: One interrupt per PWM channel.
> 
> one per channel?
> 
Each PWM instance in FU540-C000 has 4 independent comparator's 
each capable of generating interrupts.  So maxItems need to be 4 and I can 
include it in description something like:
 " description: 
        Each PWM instance in FU540-C000 has 4 comparators. One interrupt per comparator" 
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - clocks
> > +  - "#pwm-cells"
> > +  - interrupts
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    pwm:  pwm@10020000 {
> > +      compatible = "sifive,fu540-c000-pwm", "sifive,pwm0";
> > +      reg = <0x10020000 0x1000>;
> > +      clocks = <&tlclk>;
> > +      interrupt-parent = <&plic>;
> > +      interrupts = <42 43 44 45>;
> 
> Split entries:
> 
> interrupts = <42>, <43>, <44>, <45>;
> 
Yes, I will split entries as suggested.

Thanks & BR,
Sagar
> > +      #pwm-cells = <3>;
> > +    };
> > --
> > 2.7.4
> >