linux-kernel - Re: [PATCH V2 0/3] Add S4 SoC clock controller driver

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Date:   Thu, 28 Jul 2022 11:03:18 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Yu Tu <yu.tu@...ogic.com>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH V2 0/3] Add S4 SoC clock controller driver


On Thu 28 Jul 2022 at 16:55, Yu Tu <yu.tu@...ogic.com> wrote:

> Hi Jerome,
> 	Thanks for your reply and explanation.
>
> On 2022/7/28 16:27, Jerome Brunet wrote:
>> [ EXTERNAL EMAIL ]
>> 
>> On Thu 28 Jul 2022 at 16:06, Yu Tu <yu.tu@...ogic.com> wrote:
>> 
>>> Hi JB，
>>>
>>> On 2022/7/28 15:08, Jerome Brunet wrote:
>>>> [ EXTERNAL EMAIL ]
>>>>
>>>> On Thu 28 Jul 2022 at 13:41, Yu Tu <yu.tu@...ogic.com> wrote:
>>>>
>>>>> 1. Add clock controller driver for S4 SOC.
>>>>>
>>>>> Yu Tu (3):
>>>>>     dt-bindings: clk: meson: add S4 SoC clock controller bindings
>>>>>     arm64: dts: meson: add S4 Soc clock controller in DT
>>>>>     clk: meson: s4: add s4 SoC clock controller driver
>>>>>
>>>>> V1 -> V2: Change format as discussed in the email.
>>>>>
>>>>> Link:https://lore.kernel.org/linux-amlogic/20220708062757.3662-1-yu.tu@amlogic.com/
>>>>>
>>>>>    .../bindings/clock/amlogic,gxbb-clkc.txt      |    1 +
>>>>>    MAINTAINERS                                   |    1 +
>>>>>    arch/arm64/boot/dts/amlogic/meson-s4.dtsi     |   11 +
>>>>>    drivers/clk/meson/Kconfig                     |   15 +
>>>>>    drivers/clk/meson/Makefile                    |    1 +
>>>>>    drivers/clk/meson/s4.c                        | 4732 +++++++++++++++++
>>>>>    drivers/clk/meson/s4.h                        |  296 ++
>>>>>    include/dt-bindings/clock/s4-clkc.h           |  146 +
>>>>>    8 files changed, 5203 insertions(+)
>>>>>    create mode 100644 drivers/clk/meson/s4.c
>>>>>    create mode 100644 drivers/clk/meson/s4.h
>>>>>    create mode 100644 include/dt-bindings/clock/s4-clkc.h
>>>>>
>>>>>
>>>>> base-commit: b293bc9286ee21824e93f0fcfed3b78fdfee01e6
>>>> Please don't post until you have addressed *ALL* the comments from the
>>>> previous version.
>>> The last email asked you to adopt A1 method, but you did not reply?
>>>
>>>> At first glance, I can see that this is still a single driver for
>>>> what is obviously 2 controllers with 2 register spaces. Simple comments
>>>> like the "<< 2" in the register declaration have not been addressed either.
>>> I understand that this should be a controller, just two address
>>> descriptions. One is the various PLL registers and one is the clock for
>>> the peripherals. And PLL is to provide a clock source for various
>>> peripheral clocks. So a clock controller is reasonable. I think you got
>>> it wrong.
>> I don't think I do. This looks exactly like the A1.
>> The post of that controller are still in the  archive and I am sure your
>> colleagues can give you the history.
>> You clearly have register regions providing clock, separated by
>> 0x8000. Claiming that as one big region is bad design.
>> There has been several remarks about using a big syscon on V1,
>> unaddressed too.
>> CCF has everything necessary in place to handle each register region
>> separately, properly and pass clock around.
>> You can handle it as a single controller, claiming the two regions
>> individually but:
>> # 1 - handling 2 different regmaps in the controller is going to be
>>        bigger mess than you think
>> # 2 - I am far from convinced there is any reason to do so
>> 
> It makes sense, as you say, to separate the two controllers. But I think
> the only thing that was forced apart was that the digital designers 
> didn't put these registers together when they were designing the chips.
>

One controller is providing all the base PLLs
The other is providing most (if not all) the devices clocks.
This does not look like coincidence or mistake to me.

> I'm going to separate the two controllers like you said.
>
>> 
>>>
>>> Ok, if you insist on using two clock controllers,, please provide your the
>>> reason and example code?
>>>
>>>> Seeing that, I have not reviewed this version further.
>>>> I won't until all the comments from v1 are either addressed or answer
>>>> Regards
>>>> Jerome
>>>> .
>> .