linux-kernel - Re: [PATCH v6 4/6] clk: samsung: add Exynos ACPM clock driver

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Message-ID: <c5712c26-439f-4c20-8d36-4179f345cca1@kernel.org>
Date: Mon, 20 Oct 2025 13:21:54 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Tudor Ambarus <tudor.ambarus@...aro.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Peter Griffin <peter.griffin@...aro.org>,
 André Draszik <andre.draszik@...aro.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Alim Akhtar <alim.akhtar@...sung.com>,
 Sylwester Nawrocki <s.nawrocki@...sung.com>,
 Chanwoo Choi <cw00.choi@...sung.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-clk@...r.kernel.org, willmcvicker@...gle.com, kernel-team@...roid.com
Subject: Re: [PATCH v6 4/6] clk: samsung: add Exynos ACPM clock driver

On 20/10/2025 13:02, Tudor Ambarus wrote:
> 
> 
> On 10/20/25 10:58 AM, Krzysztof Kozlowski wrote:
>> On 20/10/2025 11:19, Tudor Ambarus wrote:
>>>
>>>
>>> On 10/20/25 9:22 AM, Krzysztof Kozlowski wrote:
>>>> On 20/10/2025 09:45, Tudor Ambarus wrote:
>>>>>
>>>>>
>>>>> On 10/20/25 7:54 AM, Krzysztof Kozlowski wrote:
>>>>>>> diff --git a/drivers/clk/samsung/Kconfig b/drivers/clk/samsung/Kconfig
>>>>>>> index 76a494e95027af26272e30876a87ac293bd56dfa..70a8b82a0136b4d0213d8ff95e029c52436e5c7f 100644
>>>>>>> --- a/drivers/clk/samsung/Kconfig
>>>>>>> +++ b/drivers/clk/samsung/Kconfig
>>>>>>> @@ -95,6 +95,16 @@ config EXYNOS_CLKOUT
>>>>>>>  	  status of the certains clocks from SoC, but it could also be tied to
>>>>>>>  	  other devices as an input clock.
>>>>>>>  
>>>>>>> +config EXYNOS_ACPM_CLK
>>>>>>> +	tristate "Clock driver controlled via ACPM interface"
>>>>>>> +	depends on EXYNOS_ACPM_PROTOCOL || (COMPILE_TEST && !EXYNOS_ACPM_PROTOCOL)
>>>>>>
>>>>>> I merged the patches but I don't get why we are not enabling it by
>>>>>> default, just like every other clock driver. What is so special here?
>>>>>
>>>>> Thanks! Are you referring to the depends on line? I needed it otherwise
>>>>> on randconfigs where COMPILE_TEST=y and EXYNOS_ACPM_PROTOCOL=n I get:
>>>>
>>>>
>>>> No. I am referring to missing default and defconfig patch.
>>>>
>>>
>>> default m or y would force compilation of EXYNOS_ACPM_CLK and
>>> EXYNOS_ACPM_PROTOCOL for all ARCH_EXYNOS, even on Exynos platforms that
>>> don't use ACPM. Since ACPM is not universally required by the Exynos
>>> architecture, I thought to make it opt-in (default n).
>>
>>
>> Just like every clock driver. So again - how is it different?
> 
> The key difference lies in the universality of the hardware interface
> across the ARCH_EXYNOS family. If EXYNOS_AUDSS_CLK_CON, EXYNOS_CLKOUT
> are considered core, integral, or nearly universal features across
> Exynos SoCs, then it's alright to have them by default. I can't tell how
> common is ACPM across the Samsung Exynos SoCs. I know it's present on
> gs{1,2)01 and e850. Heard it mentioned around some other phone but I
> can't remember which. Maybe we shall set to a default m when more users
> reveal themselves? I'm of course open to drop the defconfig patch and
> follow up with a patch setting EXYNOS_ACPM_CLK to
> "default m if ARCH_EXYNOS" if you think it's common enough.


OK, we can wait till one more user appears. Although the choice is less
about universality, but rather if this is a core SoC element. If this is
a core SoC element, then SoC ARCH should select it (not allow to disable
it), even if this is only for one ARCH_EXYNOS SoC.

Best regards,
Krzysztof