linux-kernel - Re: [PATCH 5/5] riscv: dts: add clock generator for Sophgo SG2042 SoC

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Date:   Wed, 15 Nov 2023 10:34:29 +0800
From:   Chen Wang <unicorn_wang@...look.com>
To:     Samuel Holland <samuel.holland@...ive.com>,
        Conor Dooley <conor@...nel.org>,
        Chen Wang <unicornxw@...il.com>
Cc:     aou@...s.berkeley.edu, chao.wei@...hgo.com,
        krzysztof.kozlowski+dt@...aro.org, mturquette@...libre.com,
        palmer@...belt.com, paul.walmsley@...ive.com,
        richardcochran@...il.com, robh+dt@...nel.org, sboyd@...nel.org,
        devicetree@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        haijiao.liu@...hgo.com, xiaoguang.xing@...hgo.com
Subject: Re: [PATCH 5/5] riscv: dts: add clock generator for Sophgo SG2042 SoC


On 2023/11/15 10:15, Samuel Holland wrote:
> On 2023-11-14 7:34 PM, Chen Wang wrote:
>> On 2023/11/15 1:31, Conor Dooley wrote:
>>> On Mon, Nov 13, 2023 at 09:20:11PM +0800, Chen Wang wrote:
>>>> From: Chen Wang <unicorn_wang@...look.com>
>>>>
>>>> Add clock generator node to device tree for SG2042, and enable clock for
>>>> uart0.
>>>>
>>>> Signed-off-by: Chen Wang <unicorn_wang@...look.com>
>>>> ---
>>>>    arch/riscv/boot/dts/sophgo/sg2042-clock.dtsi | 76 ++++++++++++++++++++
>>> There's no need to create an entirely new file for this.
>> Agree, I will merge this into sg2042.dtsi in next revision.
>>>>    arch/riscv/boot/dts/sophgo/sg2042.dtsi       | 10 +++
>>>>    2 files changed, 86 insertions(+)
>>>>    create mode 100644 arch/riscv/boot/dts/sophgo/sg2042-clock.dtsi
>>>>
>>>> diff --git a/arch/riscv/boot/dts/sophgo/sg2042-clock.dtsi
>>>> b/arch/riscv/boot/dts/sophgo/sg2042-clock.dtsi
>>>> new file mode 100644
>>>> index 000000000000..66d2723fab35
>>>> --- /dev/null
>>>> +++ b/arch/riscv/boot/dts/sophgo/sg2042-clock.dtsi
>>>> @@ -0,0 +1,76 @@
>>>> +// SPDX-License-Identifier: (GPL-2.0 OR MIT)
>>>> +/*
>>>> + * Copyright (C) 2023 Sophgo Technology Inc. All rights reserved.
>>>> + */
>>>> +
>>>> +/ {
>>>> +    cgi: oscillator {
>>>> +        compatible = "fixed-clock";
>>>> +        clock-frequency = <25000000>;
>>>> +        clock-output-names = "cgi";
>>>> +        #clock-cells = <0>;
>>>> +    };
>>> What actually is this oscillator?
>>> Is it provided by another clock controller on the SoC, or is it provided
>>> by an oscillator on the board?
>> This oscillator is an individual ic chip outside the SoC on the board, that's
>> why I list it outside soc node.
>>
>> Actually the "cgi" is abbrevation for "Clock Generation IC chip".
> Since the oscillator is outside the SoC, this node (or at least its
> clock-frequency property) belongs in the board devicetree, not the SoC .dtsi.
> See [1].
>
> Regards,
> Samuel
>
> [1]:
> https://lore.kernel.org/linux-riscv/b5401052-e803-9788-64d6-82b2737533ce@linaro.org/

Thank you Samuel, I have learned this and will correct this in next 
revision.