linux-kernel - Re: [PATCH 00/12] Add minimal support for Exynos850 SoC

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Date:   Sat, 31 Jul 2021 10:12:47 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>
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 00/12] Add minimal support for Exynos850 SoC

On 31/07/2021 09:29, Krzysztof Kozlowski wrote:
> On 30/07/2021 21:02, Sam Protsenko wrote:
>> Hi Krzysztof,
>>
>> On Fri, 30 Jul 2021 at 20:21, Krzysztof Kozlowski
>> <krzysztof.kozlowski@...onical.com> wrote:
>>>
>>> On 30/07/2021 17:18, Krzysztof Kozlowski wrote:
>>>> On 30/07/2021 16:49, Sam Protsenko wrote:
>>>>> This patch series adds initial platform support for Samsung Exynos850
>>>>> SoC [1]. With this patchset it's possible to run the kernel with BusyBox
>>>>> rootfs as a RAM disk. More advanced platform support (like MMC driver
>>>>> additions) will be added later. The idea is to keep the first submission
>>>>> minimal to ease the review, and then build up on top of that.
>>>>>
>>>>> [1] https://www.samsung.com/semiconductor/minisite/exynos/products/mobileprocessor/exynos-850/
>>>>>
>>>>
>>>> Great work!
>>>>
>>
>> Thanks, Krzysztof! And thank you for reviewing the whole series.
>>
>>>> What's the SoC revision number (should be accessible via
>>>> /sys/bus/soc/devices/soc0/)? Recent wrap in numbering of Exynos chips
>>>> might bring confusion...
>>
>> # cat /sys/devices/soc0/revision
>> 0
> 
> soc_id but you're right it won't be set for unknown SoCs. You need to
> extend drivers/soc/samsung/exynos-chipid.c to parse new values (E3830000
> for product ID) and maybe new register offsets (previous offset is 0x0,
> for 3830 is 0x10 I think). Also revision mask might change.
> 
>>> Judging by vendor's sources it is quite confusing. It looks mostly like
>>> Exynos3830 but in few other cases it uses Exynos9 compatibles (Exynos9,
>>> Exynos9820). Only in few places there is Exynos850. Marketing department
>>> made it so confusing...  The revision embedded in SoC would be very
>>> interesting.
>>>
>>
>> As I understand, this SoC is called Exynos850 everywhere now.
>> Exynos3830 is its old name, not used anymore. As you noticed from
>> patch #2, it shares some definitions with Exynos9 SoC, so I guess some
>> software is similar for both architectures. Not sure about hardware
>> though, never worked with Exynos9 CPUs. Anyway, I asked Samsung
>> representatives about naming, and it seems like we should stick to
>> "Exynos850" name, even in code.
> 
> 
> Since the chip identifies itself as E3830000, I would prefer naming
> matching real product ID instead of what is pushed by marketing or sales
> representatives. The marketing names don't have to follow any
> engineering rules, they can be changed and renamed. Sales follows rather
> money and corporate rules, not consistency for upstream project.

On the other hand we have already two exceptions for naming
inconsistency - Exynos3250 identifies itself as 3472 (which is confusing
because 3250 is two core and there is a separate quad-core
Exyons3472...) and Exynos5800 is actually marketing name for a revision
of Exynos5422. Maybe indeed will be easier to go with the branded name
850...


Best regards,
Krzysztof