linux-kernel - Re: [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock

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Message-ID: <20210806082818.k3awj72j2yb2bbhe@pali>
Date:   Fri, 6 Aug 2021 10:28:18 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Vladimir Vid <vladimir.vid@...tura.hr>, kabel@...nel.org,
        linux-clk@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for
 marvell,armada-3700-uart-clock

On Thursday 05 August 2021 17:30:19 Stephen Boyd wrote:
> > diff --git a/Documentation/devicetree/bindings/clock/armada3700-uart-clock.yaml b/Documentation/devicetree/bindings/clock/armada3700-uart-clock.yaml
> > new file mode 100644
> > index 000000000000..5ef04f3affda
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/armada3700-uart-clock.yaml
> > @@ -0,0 +1,49 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/clock/marvell,armada-3700-uart-clock#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +title: Marvell Armada 3720 UART clocks
> 
> Please add a newline here
> 
> > +properties:
> > +  compatible:
> > +    const: marvell,armada-3700-uart-clock
> 
> Please add a newline here
> 
> > +  reg:
> > +    items:
> > +      - description: UART Clock Control Register
> > +      - description: UART 2 Baud Rate Divisor Register
> 
> Please add a newline here
> 
> > +  clocks:
> > +    description: |
> > +      List of parent clocks suitable for UART from following set:
> > +        "TBG-A-P", "TBG-B-P", "TBG-A-S", "TBG-B-S", "xtal"
> > +      UART clock can use one from this set and when more are provided
> > +      then kernel would choose and configure the most suitable one.
> > +      It is suggest to specify at least one TBG clock to achieve
> > +      baudrates above 230400 and also to specify clock which bootloader
> > +      used for UART (most probably xtal) for smooth boot log on UART.
> 
> Please use items and const like clock-names for the clocks property.

It is already there, see below.

> The description makes me feel like the DT is configuring the choices
> available.

See description. It is kernel (driver) who is choosing one clock from
the set and then configure it a UART clock.

> Ideally, the clocks and clock-names properties are fixed in
> length and never change unless the compatible changes.
> 
> Please add a newline here
> 
> > +  clock-names:
> > +    items:
> > +      - const: TBG-A-P
> > +      - const: TBG-B-P
> > +      - const: TBG-A-S
> > +      - const: TBG-B-S
> > +      - const: xtal
> > +    minItems: 1
> > +    maxItems: 5
> 
> Please add a newline here
> 
> > +  '#clock-cells':
> > +    const: 1
> 
> Please add a newline here
> 
> > +required:
> > +  - compatible
> > +  - reg
> > +  - clocks
> > +  - clock-names
> > +  - '#clock-cells'
> 
> Please add a newline here
> 
> > +additionalProperties: false
> 
> Please add a newline here
> 
> > +examples:
> > +  - |
> > +    uartclk: uartclk@...00 {
> > +      compatible = "marvell,armada-3700-uart-clock";
> > +      reg = <0x12010 0x4>, <0x12210 0x4>;
> > +      clocks = <&tbg 0>, <&tbg 1>, <&tbg 2>, <&tbg 3>, <&xtalclk>;
> > +      clock-names = "TBG-A-P", "TBG-B-P", "TBG-A-S", "TBG-B-S", "xtal";
> > +      #clock-cells = <1>;
> > +    };