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

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Date:   Thu, 28 Jul 2022 17:52:57 +0800
From:   Yu Tu <yu.tu@...ogic.com>
To:     Jerome Brunet <jbrunet@...libre.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 2022/7/28 17:03, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
> 
> 
> 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.
Thanks for your reply. Looks like I got it wrong. However, I will talk 
to the chip designer about whether it is possible to put these registers 
in the later chip so that it may be easier for our software to process.

> 
>> 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
>>>>> .
>>> .
> 
> .