linux-kernel - Re: [PATCH v4 01/13] dt-bindings: clk: g12a-clkc: export VCLK2_SEL and add CTS

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Message-ID: <9cba6384-123b-1cd1-ed02-08365a0ed529@linaro.org>
Date:   Mon, 15 May 2023 18:22:52 +0200
From:   neil.armstrong@...aro.org
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Kevin Hilman <khilman@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>
Cc:     Nicolas Belin <nbelin@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-phy@...ts.infradead.org
Subject: Re: [PATCH v4 01/13] dt-bindings: clk: g12a-clkc: export VCLK2_SEL
 and add CTS_ENCL clock ids

On 15/05/2023 18:15, Krzysztof Kozlowski wrote:
> On 15/05/2023 18:13, Krzysztof Kozlowski wrote:
>> On 15/05/2023 18:06, Neil Armstrong wrote:
>>> On 13/05/2023 20:28, Krzysztof Kozlowski wrote:
>>>> On 12/05/2023 15:11, Neil Armstrong wrote:
>>>>> Expose VCLK2_SEL clock id and add new ids for the CTS_ENCL and CTS_ENCL_SEL
>>>>> clocks on G12A compatible SoCs.
>>>>>
>>>>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>>>>> ---
>>>>>    drivers/clk/meson/g12a.h              | 1 -
>>>>>    include/dt-bindings/clock/g12a-clkc.h | 3 +++
>>>>>    2 files changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> Bindings must be a separate patch from the driver changes. If this
>>>> causes bisectability issues, this means entire solution breaks ABI and
>>>> is not appropriate anyway...
>>>
>>> This is basically how we handled CLK IDs on Amlogic clk bindings for the
>>> last years, the amount of changes is very low and rather exceptional
>>> compared to early development stage.
>>
>> The commits with bindings are used in devicetree-rebasing repo, so we
>> want them to be separate.

A lot of commits changes the bindings and other part of the kernel source,
it was solved with git filter-repo a long time ago.
While I understand in an ideal world those commits should only touch
Documentation/bindings, it's sometime not possible.

>>
>> Meson is the only or almost the only platform making such changes. I
>> don't get why, because the conflict could be easily avoided with using
>> different names for defines in bindings and local clock. Approach of
>> having bindings strictly tied with driver commit is never desired.

If we did it now, we would have make it differently and expose all the clock
IDs on the bindings like on Qcom, be sure of that.

> 
> Also one more argument maybe not relevant here but for other cases -
> this makes literally impossible to include the clock ID in DTS in the
> same kernel revision, because you must not merge driver branch to DTS
> branch. SoC folks were complaining about this many times.

Actually we handle this very simply by having such patches merged in a immutable
branch merged in the clock and DT pull-requests, it worked perfectly so far
and neither Stephen or Arnd complained about that.

> 
> Best regards,
> Krzysztof
>