linux-kernel - Re: [PATCH v3 6/7] dt-bindings: clock: meson: add A1 CPU clock controller bindings

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Date: Mon, 10 Jun 2024 14:18:26 +0300
From: Dmitry Rokosov <ddrokosov@...utedevices.com>
To: Jerome Brunet <jbrunet@...libre.com>
CC: <neil.armstrong@...aro.org>, <mturquette@...libre.com>,
	<sboyd@...nel.org>, <robh+dt@...nel.org>,
	<krzysztof.kozlowski+dt@...aro.org>, <khilman@...libre.com>,
	<martin.blumenstingl@...glemail.com>, <jian.hu@...ogic.com>,
	<kernel@...rdevices.ru>, <rockosov@...il.com>,
	<linux-amlogic@...ts.infradead.org>, <linux-clk@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v3 6/7] dt-bindings: clock: meson: add A1 CPU clock
 controller bindings

Hello Jerome,

Thank you for the review!

On Mon, Jun 10, 2024 at 12:04:09PM +0200, Jerome Brunet wrote:
> On Wed 15 May 2024 at 21:47, Dmitry Rokosov <ddrokosov@...utedevices.com> wrote:
> 
> > Add the documentation and dt bindings for Amlogic A1 CPU clock
> > controller.
> >
> > This controller consists of the general 'cpu_clk' and two main parents:
> > 'cpu fixed clock' and 'syspll'. The 'cpu fixed clock' is an internal
> > fixed clock, while the 'syspll' serves as an external input from the A1
> > PLL clock controller.
> >
> > Signed-off-by: Dmitry Rokosov <ddrokosov@...utedevices.com>
> > Reviewed-by: Rob Herring <robh@...nel.org>
> > ---
> >  .../bindings/clock/amlogic,a1-cpu-clkc.yaml   | 64 +++++++++++++++++++
> >  .../dt-bindings/clock/amlogic,a1-cpu-clkc.h   | 19 ++++++
> >  2 files changed, 83 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/clock/amlogic,a1-cpu-clkc.yaml
> >  create mode 100644 include/dt-bindings/clock/amlogic,a1-cpu-clkc.h
> >
> > diff --git a/Documentation/devicetree/bindings/clock/amlogic,a1-cpu-clkc.yaml b/Documentation/devicetree/bindings/clock/amlogic,a1-cpu-clkc.yaml
> > new file mode 100644
> > index 000000000000..f4958b315ed4
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/amlogic,a1-cpu-clkc.yaml
> > @@ -0,0 +1,64 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/clock/amlogic,a1-cpu-clkc.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Amlogic A1 CPU Clock Control Unit
> > +
> > +maintainers:
> > +  - Neil Armstrong <neil.armstrong@...aro.org>
> > +  - Jerome Brunet <jbrunet@...libre.com>
> > +  - Dmitry Rokosov <ddrokosov@...utedevices.com>
> > +
> > +properties:
> > +  compatible:
> > +    const: amlogic,a1-cpu-clkc
> > +
> > +  '#clock-cells':
> > +    const: 1
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    items:
> > +      - description: input fixed pll div2
> > +      - description: input fixed pll div3
> > +      - description: input sys pll
> > +      - description: input oscillator (usually at 24MHz)
> 
> According to the documentation, fdiv5 is also an input of the CPU clock
> tree.
> 
> That is typically the kind of things we'd prefer to get right from the
> beginning to avoid modifying the bindings later.
> 

Could you please share which documentation you are referencing? I have
the A113L documentation, and there is no mention of the CPU clock IP.
I retrieved below register map from the vendor's custom driver:

===
CPUCTRL_CLK_CTRL0

bits 1:0 - cpu_fsource_sel0
    0 - xtal
    1 - fclk_div2
    2 - fclk_div3

bit 2 - cpu_fsel0
    0 - cpu_fsource_sel0
    1 - cpu_fsource_div0

bit 3 - UNKNONWN

bits 9:4 - cpu_fsource_div0
    Divider value

bit 10 - cpu_fclk
    0 - cpu_fsel0
    1 - cpu_fsel1

bit 11 - cpu_clk
    0 - cpu_fclk
    1 - sys_pll

bits 15:12 - UNKNONWN

bits 17:16 - cpu_fsource_sel1
    0 - xtal
    1 - fclk_div2
    2 - fclk_div3

bit 18 - cpu_fsel1
    0 - cpu_fsource_sel1
    1 - cpu_fsource_div1

bit 19 - UNKNONWN

bits 25:20 - cpu_fsource_div1
    Divider value

bits 31:26 - UNKNONWN
===

As you can see it doesn't have any other inputs except fclk_div2,
fclk_div3, sys_pll and xtal.

> > +
> > +  clock-names:
> > +    items:
> > +      - const: fclk_div2
> > +      - const: fclk_div3
> > +      - const: sys_pll
> > +      - const: xtal
> > +
> > +required:
> > +  - compatible
> > +  - '#clock-cells'
> > +  - reg
> > +  - clocks
> > +  - clock-names
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/clock/amlogic,a1-pll-clkc.h>
> > +    apb {
> > +        #address-cells = <2>;
> > +        #size-cells = <2>;
> > +
> > +        clock-controller@...00000 {
> > +            compatible = "amlogic,a1-cpu-clkc";
> > +            reg = <0 0xfd000080 0 0x8>;
> 
> If reg is <0 0xfd000080 0 0x8> then node name should be clock-controller@...00080
> 

Okay, I will fix that example in the next version.

[...]

-- 
Thank you,
Dmitry