linux-kernel - Re: [PATCH 12/12] arm64: dts: exynos: Add Exynos850 SoC support

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Date:   Fri, 6 Aug 2021 14:32:00 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>
Cc:     Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
        Ryu Euiyoul <ryu.real@...sung.com>,
        Tom Gall <tom.gall@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH 12/12] arm64: dts: exynos: Add Exynos850 SoC support

On 06/08/2021 14:07, Sam Protsenko wrote:
> On Fri, 6 Aug 2021 at 10:49, Krzysztof Kozlowski
> <krzysztof.kozlowski@...onical.com> wrote:
>>
>> On 06/08/2021 01:06, Sam Protsenko wrote:
>>> On Sat, 31 Jul 2021 at 12:03, Krzysztof Kozlowski
>>> <krzysztof.kozlowski@...onical.com> wrote:
>>>
>>>>>
>>>>> This patch adds minimal SoC support. Particular board device tree files
>>>>> can include exynos850.dtsi file to get SoC related nodes, and then
>>>>> reference those nodes further as needed.
>>>>>
>>>>> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
>>>>> ---
>>>>>  .../boot/dts/exynos/exynos850-pinctrl.dtsi    | 782 ++++++++++++++++++
>>>>>  arch/arm64/boot/dts/exynos/exynos850-usi.dtsi |  30 +
>>>>>  arch/arm64/boot/dts/exynos/exynos850.dtsi     | 245 ++++++
>>>>
>>>> Not buildable. Missing Makefile, missing DTS. Please submit with initial
>>>> DTS, otherwise no one is able to verify it even compiles.
>>>>
>>>
>>> This device is not available for purchase yet. I'll send the patch for
>>> board dts once it's announced. I can do all the testing for now, if
>>> you have any specific requests. Would it be possible for us to review
>>> and apply only SoC support for now? Will send v2 soon...
>>
>> What you propose is equal to adding a driver (C source code) without
>> ability to compile it. What's the point of having it in the kernel? It's
>> unverifiable, unbuildable and unusable.
>>
> 
> Yes, I understand. That's adding code with no users, and it's not a
> good practice.
> 
>> We can review the DTSI however merging has to be with a DTS. Usually the
>> SoC vendor adds first an evalkit (e.g. SMDK board). Maybe you have one
>> for Exynos850? Otherwise if you cannot disclose the actual board, the
>> DTSI will have to wait. You can submit drivers, though.
>>
> 
> Sure, let's go this way. I'll send v2 soon. Improving patches and
> having Reviewed-by tag for those would good enough for me at this
> point. I'll continue to prepare another Exynos850 related patches
> until the actual board is announced, like proper clock driver, reset,
> MMC, etc. Is it ok if I send those for a review too (so I can fix all
> issues ahead)?

Sure, prepare all necessary drivers earlier. I suspect clocks will be a
real pain because of significant changes modeled in vendor kernel. I
remember Paweł Chmiel (+Cc) was doing something for these:
https://github.com/PabloPL/linux/tree/exynos7420

I mentioned before - you should also modify the chipid driver. Check
also other drivers in drivers/soc/samsung, although some are needed only
for suspend&resume.

BTW, Paweł,
How is your Exynos7420 progress? :)

> And should I maybe add RFC tag for those?

No need. Drivers can be merged before DTS users.

Best regards,
Krzysztof