linux-kernel - Re: [PATCH 4/6] dt-bindings: clock: Add bindings definitions for Exynos850 CMU

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Date:   Wed, 6 Oct 2021 12:49:24 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Chanwoo Choi <cwchoi00@...il.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc:     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>,
        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>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH 4/6] dt-bindings: clock: Add bindings definitions for
 Exynos850 CMU

On 05/10/2021 12:28, Sam Protsenko wrote:
> On Wed, 15 Sept 2021 at 19:37, Chanwoo Choi <cwchoi00@...il.com> wrote:
>>
>> Hi,
>>
>> You don't add clock ids for the all defined clocks in clk-exynos850.c.
>> I recommend that add all clock ids for the defined clocks if possible.
>>
>> If you want to change the parent clock of mux or change the clock rate
>> of div rate for some clocks, you have to touch the files as following:
>> - include/dt-bindings/clock/exynos850.h
>> - drivers/clk/samsung/clk-exynos850.c
>> - exynos850 dt files
>>
>> If you define the clock ids for all clocks added to this patchset,
>> you can change the parent or rate by just editing the dt files.
>>
> 
> Hi Chanwoo,
> 
> I see your point. But I have intentionally omitted some clock ids,
> which can't be / shouldn't be used by consumers in device tree.
> Actually I took that idea from clk-exynos7.c.
> 
> Krzysztof, Sylwester: can you please advice if all clock ids should be
> defined, or only those that are going to be used in dts clk consumers?
> I don't mind reworking the patch, just want to be sure which design
> approach we want to follow.
> 

I would advise to define all clock IDs, unless the clock really, really
should not be used. Why do you think several clocks should not be used?
Have in mind it is not only about consumers but also clock reparenting
and assigning rates.


Best regards,
Krzysztof