linux-kernel - Re: [RFC PATCH 12/36] platform: arm64: Move ec devices to an ec subdirectory

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Message-ID: <bd30c235-a403-4d81-9bfa-3f6a15450f23@arm.com>
Date: Wed, 6 Aug 2025 19:03:18 +0100
From: James Morse <james.morse@....com>
To: Ben Horgan <ben.horgan@....com>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Cc: Rob Herring <robh@...nel.org>, Rohit Mathew <rohit.mathew@....com>,
 Shanker Donthineni <sdonthineni@...dia.com>, Zeng Heng
 <zengheng4@...wei.com>, Lecopzer Chen <lecopzerc@...dia.com>,
 Carl Worth <carl@...amperecomputing.com>,
 shameerali.kolothum.thodi@...wei.com,
 D Scott Phillips OS <scott@...amperecomputing.com>, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>
Subject: Re: [RFC PATCH 12/36] platform: arm64: Move ec devices to an ec
 subdirectory

Hi Ben,

On 24/07/2025 11:56, Ben Horgan wrote:
> On 11/07/2025 19:36, James Morse wrote:
>> commit 363c8aea257 "platform: Add ARM64 platform directory" added a
>> subdirectory for arm64 platform devices, but claims that all such
>> devices must be 'EC like'.
>>
>> The arm64 MPAM driver manages an MMIO interface that appears in memory
>> controllers, caches, IOMMU and connection points on the interconnect.
>> It doesn't fit into any existing subsystem.
>>
>> It would be convenient to use this subdirectory for drivers for other
>> arm64 platform devices which aren't closely coupled to the architecture
>> code and don't fit into any existing subsystem.
>>
>> Move the existing code and maintainer entries to be under
>> drivers/platform/arm64/ec. The MPAM driver will be added under
>> drivers/platform/arm64/mpam.


>> diff --git a/drivers/platform/arm64/ec/Kconfig b/drivers/platform/arm64/ec/Kconfig
>> new file mode 100644
>> index 000000000000..06288aebc559
>> --- /dev/null
>> +++ b/drivers/platform/arm64/ec/Kconfig
>> @@ -0,0 +1,73 @@
>> +# SPDX-License-Identifier: GPL-2.0-only
>> +#
>> +# EC-like Drivers for aarch64 based devices.
>> +#
>> +
>> +menuconfig ARM64_PLATFORM_DEVICES
>> +    bool "ARM64 Platform-Specific Device Drivers"
>> +    depends on ARM64 || COMPILE_TEST
>> +    default ARM64
>> +    help
>> +      Say Y here to get to see options for platform-specific device drivers
>> +      for arm64 based devices, primarily EC-like device drivers.
>> +      This option alone does not add any kernel code.
>> +
>> +      If you say N, all options in this submenu will be skipped and disabled.
>> +
>> +if ARM64_PLATFORM_DEVICES

> Shouldn't this be kept in the directory above? By the description this would be expected
> to apply to all drivers in drivers/platfrom/arm64.

Doing that makes any MPAM options appear under 'Platform-Specific Device Drivers' too. I
didn't to that as MPAM isn't specific to one platform, but doesn't fit under any of the
bus or high level groups under drivers. (I briefly toyed with drivers/perf - as there
isn't a drivers/qos).


Thanks,

James