linux-kernel - Re: [PATCH v2 4/5] firmware: exynos-acpm: register ACPM clocks dev

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Message-ID: <44d8a998-efe7-4c2f-8580-5248b1a98c44@kernel.org>
Date: Mon, 1 Sep 2025 11:34:00 +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 v2 4/5] firmware: exynos-acpm: register ACPM clocks dev

On 01/09/2025 10:43, Tudor Ambarus wrote:
> 
> 
> On 9/1/25 8:48 AM, Krzysztof Kozlowski wrote:
>> On 01/09/2025 08:56, Tudor Ambarus wrote:
>>>
>>>
>>> On 8/31/25 11:50 AM, Krzysztof Kozlowski wrote:
>>>> On 27/08/2025 14:42, Tudor Ambarus wrote:
>>>>> +
>>>>> +static const struct acpm_clk_variant gs101_acpm_clks[] = {
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_MIF, "mif"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_INT, "int"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_CPUCL0, "cpucl0"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_CPUCL1, "cpucl1"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_CPUCL2, "cpucl2"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_G3D, "g3d"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_G3DL2, "g3dl2"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_TPU, "tpu"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_INTCAM, "intcam"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_TNR, "tnr"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_CAM, "cam"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_MFC, "mfc"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_DISP, "disp"),
>>>>> +	ACPM_CLK(CLK_ACPM_DVFS_BO, "b0"),
>>>>> +};
>>>>
>>>> I don't understand why clocks are defined in the firmware driver, not in
>>>> the clock driver.
>>>
>>> I chose to define the clocks in the firmware driver and pass them as 
>>> platform data to the clock platform device for extensibility. In case
>>> other SoCs have different clock IDs, they'll be able to pass the
>>
>> You will have to modify firmware driver, so still at least one driver
>> has to be changed. Having clocks defined in non-clock driver is really
>> unusual.
>>
>> This solution here creates also dependency on clock bindings and makes
>> merging everything unnecessary difficult.
>>
>>> clock data without needing to modify the clock driver. GS201 defines
>>> the same ACPM clocks as GS101, but I don't have access to other newer
>>> SoCs to tell if the ACPM clocks differ or not.
>>>
>>> The alternative is to define the clocks in the clock driver and
>>> use platform_device_register_simple() to register the clock platform
>>> device. The clock driver will be rigid in what clocks it supports.
>>>
>>> I'm fine either way for now. What do you prefer?
>>
>> Please move them to the driver.
> 
> Okay, will move the clock definitions to the clock driver.
> 
>>
>>>
>>>>
>>>> This creates dependency of this patch on the clock patch, so basically
>>>> there is no way I will take it in one cycle.
>>>
>>> Would it work to have an immutable tag for the clock and samsung-soc
>>> subsytems to use?
>>
>> No, just try yourself. Patch #3 depends on patch #2, so that's the cross
>> tree merge. It's fine, but now patch #4 depends on patch #3, so you need
>> two merges.
>>
>> Or how do you actually see it being merged with immutable tag? What goes
>> where?
>>
> 
> Unnecessary difficult indeed. Hypothetically, if we kept the current

No, it is impossible.

> structure, we could have have a single tag on #4. Since the dependency was

What does it mean tag on #4? There are no further users, so tagging this
patch has zero effect.

> on a new clock driver, the clock subsystem could have lived without merging
> the tag, as the chances of conflicts with the clk core are small. But not

Quick look tells me nothing would compile. Really, try yourself. Neither
patch #3 nor patch #4 builds!

Best regards,
Krzysztof