linux-kernel - Re: [PATCH 2/2] clk: samsung: exynos850: Implement CMU

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Message-ID: <CAPLW+4mx67JcSk21ntac=WGM27GA0wMFU-r6zAHi+5i6UKMNrw@mail.gmail.com>
Date:   Sat, 23 Oct 2021 01:31:37 +0300
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Chanwoo Choi <cwchoi00@...il.com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH 2/2] clk: samsung: exynos850: Implement CMU_APM domain

On Sat, 23 Oct 2021 at 01:18, Chanwoo Choi <cwchoi00@...il.com> wrote:
>
> On 21. 10. 22. 오후 10:39, Sam Protsenko wrote:
> > On Fri, 22 Oct 2021 at 11:58, Chanwoo Choi <cwchoi00@...il.com> wrote:
> >>
> >> On 21. 10. 22. 오전 5:31, Sam Protsenko wrote:
> >>> CMU_APM clock domain provides clocks for APM IP-core (Active Power
> >>> Management). According to Exynos850 TRM, CMU_APM generates I3C, Mailbox,
> >>> Speedy, Timer, WDT, RTC and PMU clocks for BLK_ALIVE.
> >>>
> >>> This patch adds next clocks:
> >>>     - bus clocks in CMU_TOP needed for CMU_APM
> >>>     - all internal CMU_APM clocks
> >>>     - leaf clocks for I3C, Speedy and RTC IP-cores
> >>>     - bus clocks for CMU_CMGP and CMU_CHUB
> >>>
> >>> CMU_APM doesn't belong to Power Domains, but platform driver is used for
> >>> its registration to keep its bus clock always running. Otherwise rtc-s3c
> >>> driver disables that clock and system freezes.
> >>>
> >>> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> >>> ---

...snip...

> >> Basically, you can never change the already defined clock id
> >> in nclude/dt-bindings/clock/*.h because of supporting
> >> the compatibility of dtb files which were using the
> >> already defined clock id instead of changed clock id
> >>
> >> If you want to add new clock with new clock id,
> >> you have to define the new clock id at the end of defined clock
> >> like the next of CLK_GOUT_PERI_IP for TOP domain case.
> >>
> >
> > Thanks for explaining that in details, Chanwoo. As Krzysztof pointed
> > out, right now there are no dts users of this clock driver in upstream
> > kernel (I didn't submit it yet), so it'd nice if this one can be taken
> > as is. In future I'll increment the last clock ID. Guess it was my OCD
> > talking, trying to keep all clock IDs grouped by clock type :)
>
> I know that there are no user for this clock. So that it doesn't make
> the real break for compatibility. But, when some kernel developers might
> check the kernel history by git command, they never know the history
> only we know. If there are any critical reason, I don't prefer to break
> the rule of clock id defintion for patch history.
>
> Just I want to keep the original rule of clock id patch in order to remove
> the potential confusion. It is not a strong objection. But In my case,
> I cannot reply the ack. Thanks for your work.
>

Actually I was thinking about the same -- setting a bad example and
stuff. It's not a big deal, I'll send v2 soon :)

> --
> Best Regards,
> Samsung Electronics
> Chanwoo Choi