[PATCH V5 1/4] clk: meson: S4: add support for Amlogic S4 SoC PLL clock driver and bindings

[Jerome Brunet]

On Wed 23 Nov 2022 at 14:53, Krzysztof Kozlowski <krzysztof.kozlowski at linaro.org> wrote:

> On 23/11/2022 14:23, Neil Armstrong wrote:
>> Hi,
>> 
>> On 23/11/2022 12:16, Yu Tu wrote:
>>> Hi Krzysztof,
>>>      Thank you for your reply.
>>>
>>> On 2022/11/23 18:08, Krzysztof Kozlowski wrote:
>>>> [ EXTERNAL EMAIL ]
>>>>
>>>> On 23/11/2022 03:13, Yu Tu wrote:
>>>>> Add the S4 PLL clock controller found and bindings in the s4 SoC family.
>>>>>
>>>>> Signed-off-by: Yu Tu <yu.tu at amlogic.com>
>>>>> ---
>>>>>   .../bindings/clock/amlogic,s4-pll-clkc.yaml   |  51 +
>>>>
>>>> This is v5 and still bindings are here? Bindings are always separate
>>>> patches. Use subject prefixes matching the subsystem (git log --oneline
>>>> -- ...).
>>>>
>>>> And this was split, wasn't it? What happened here?!?
>>>
>>> Put bindings and clock driver patch together from Jerome. Maybe you can read this chat history.
>>> https://lore.kernel.or/all/1jy1v6z14n.fsf@starbuckisacylon.baylibre.com/
>> 
>> Jerome was asking you to send 2 patchsets, one with :
>> - bindings in separate patches
>> - drivers in separate patches
>> and a second with DT changes.

Indeed, this is what was asked. It is aligned with Krzysztof's request.

>> 
>> Then when the bindings + clocks patches are merged, a pull request of the bindings
>> can be done to me so I can merge it with DT.
>> 
>>>
>>>>
>>>>
>>>>>   MAINTAINERS                                   |   1 +
>>>>>   drivers/clk/meson/Kconfig                     |  13 +
>>>>>   drivers/clk/meson/Makefile                    |   1 +
>>>>>   drivers/clk/meson/s4-pll.c                    | 875 ++++++++++++++++++
>>>>>   drivers/clk/meson/s4-pll.h                    |  88 ++
>>>>>   .../dt-bindings/clock/amlogic,s4-pll-clkc.h   |  30 +
>>>>>   7 files changed, 1059 insertions(+)
>>>>>   create mode 100644 Documentation/devicetree/bindings/clock/amlogic,s4-pll-clkc.yaml
>>>>>   create mode 100644 drivers/clk/meson/s4-pll.c
>>>>>   create mode 100644 drivers/clk/meson/s4-pll.h
>>>>>   create mode 100644 include/dt-bindings/clock/amlogic,s4-pll-clkc.h
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/clock/amlogic,s4-pll-clkc.yaml b/Documentation/devicetree/bindings/clock/amlogic,s4-pll-clkc.yaml
>>>>> new file mode 100644
>>>>> index 000000000000..fd517e8ef14f
>>>>> --- /dev/null
>>>>> +++ b/Documentation/devicetree/bindings/clock/amlogic,s4-pll-clkc.yaml
>>>>> @@ -0,0 +1,51 @@
>>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>>> +%YAML 1.2
>>>>> +---
>>>>> +$id: http://devicetree.org/schemas/clock/amlogic,s4-pll-clkc.yaml#
>>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>>> +
>>>>> +title: Amlogic Meson S serials PLL Clock Controller
>>>>> +
>>>>> +maintainers:
>>>>> +  - Neil Armstrong <narmstrong at baylibre.com>
>>>>> +  - Jerome Brunet <jbrunet at baylibre.com>
>>>>> +  - Yu Tu <yu.hu at amlogic.com>
>>>>> +
>>>> One blank line.
>>>
>>>   I will delete this, on next version patch.
>>>
>>>>
>>>>> +
>>>>> +properties:
>>>>> +  compatible:
>>>>> +    const: amlogic,s4-pll-clkc
>>>>> +
>>>>> +  reg:
>>>>> +    maxItems: 1
>>>>> +
>>>>> +  clocks:
>>>>> +    maxItems: 1
>>>>> +
>>>>> +  clock-names:
>>>>> +    items:
>>>>> +      - const: xtal
>>>>> +
>>>>> +  "#clock-cells":
>>>>> +    const: 1
>>>>> +
>>>>> +required:
>>>>> +  - compatible
>>>>> +  - reg
>>>>> +  - clocks
>>>>> +  - clock-names
>>>>> +  - "#clock-cells"
>>>>> +
>>>>> +additionalProperties: false
>>>>> +
>>>>> +examples:
>>>>> +  - |
>>>>> +    clkc_pll: clock-controller at fe008000 {
>>>>> +      compatible = "amlogic,s4-pll-clkc";
>>>>> +      reg = <0xfe008000 0x1e8>;
>>>>> +      clocks = <&xtal>;
>>>>> +      clock-names = "xtal";
>>>>> +      #clock-cells = <1>;
>>>>> +    };
>>>>
>>>>
>>>>> +#endif /* __MESON_S4_PLL_H__ */
>>>>> diff --git a/include/dt-bindings/clock/amlogic,s4-pll-clkc.h b/include/dt-bindings/clock/amlogic,s4-pll-clkc.h
>>>>> new file mode 100644
>>>>> index 000000000000..345f87023886
>>>>> --- /dev/null
>>>>> +++ b/include/dt-bindings/clock/amlogic,s4-pll-clkc.h
>>>>
>>>> This belongs to bindings patch, not driver.
>>>>
>>>>> @@ -0,0 +1,30 @@
>>>>> +/* SPDX-License-Identifier: (GPL-2.0+ OR MIT) */
>>>>> +/*
>>>>> + * Copyright (c) 2021 Amlogic, Inc. All rights reserved.
>>>>> + * Author: Yu Tu <yu.tu at amlogic.com>
>>>>> + */
>>>>> +
>>>>> +#ifndef _DT_BINDINGS_CLOCK_AMLOGIC_S4_PLL_CLKC_H
>>>>> +#define _DT_BINDINGS_CLOCK_AMLOGIC_S4_PLL_CLKC_H
>>>>> +
>>>>> +/*
>>>>> + * CLKID index values
>>>>> + */
>>>>> +
>>>>> +#define CLKID_FIXED_PLL            1
>>>>> +#define CLKID_FCLK_DIV2            3
>>>>
>>>> Indexes start from 0 and are incremented by 1. Not by 2.
>>>>
>>>> NAK.
>>>
>>> I remember Jerome discussing this with you.You can look at this submission history.
>>> https://lore.kernel.org/all/c088e01c-0714-82be-8347-6140daf56640@linaro.org/
>> 
>> Historically we did that by only exposing part of the numbers, controlling which
>> clocks were part of the bindings.
>> 
>> But it seems this doesn't make sens anymore, maybe it would be time to put all the
>> clock ids in the bindings for this new SoC and break with the previous strategy.

Krzysztof and I agreed there is nothing wrong with the current
approach, I believe.

It does not prevent someone from using an un-exposed clock, sure, or
exposing it in the future if necessary.

However, I think it clearly shows that an un-exposed element is not
expected to be used by an external consumers. It should be enough to
trigger a discussion if this expectation is wrong.

>
> So the outcome of the previous discussion was somewhere later in that
> thread:
>
>> It is just a choice to not expose some IDs.
>> It is not tied to the implementation at all.
>> I think we actually follow the rules and the idea behind it.
>
>
> Best regards,
> Krzysztof