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Date:   Fri, 23 Jun 2023 10:57:38 -0500
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Subject: Re: [PATCH V4 1/8] drivers/acpi: Add support for Wifi band RF
 mitigations
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To:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Evan Quan <evan.quan@amd.com>
Cc:     lenb@kernel.org, alexander.deucher@amd.com,
        christian.koenig@amd.com, Xinhui.Pan@amd.com, airlied@gmail.com,
        daniel@ffwll.ch, johannes@sipsolutions.net, davem@davemloft.net,
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        mdaenzer@redhat.com, maarten.lankhorst@linux.intel.com,
        tzimmermann@suse.de, hdegoede@redhat.com, jingyuwang_vip@163.com,
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        andrealmeid@igalia.com, trix@redhat.com, jsg@jsg.id.au,
        arnd@arndb.de, linux-kernel@vger.kernel.org,
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References: <20230621054603.1262299-1-evan.quan@amd.com>
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 <CAJZ5v0iqy0yMJP5H7ub67R8R6i42=TcS_6+VF-+fWrM-9tYFQA@mail.gmail.com>
From:   "Limonciello, Mario" <mario.limonciello@amd.com>
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On 6/23/2023 9:52 AM, Rafael J. Wysocki wrote:
> On Wed, Jun 21, 2023 at 7:47 AM Evan Quan <evan.quan@amd.com> wrote:
>> From: Mario Limonciello <mario.limonciello@amd.com>
>>
>> Due to electrical and mechanical constraints in certain platform designs
>> there may be likely interference of relatively high-powered harmonics of
>> the (G-)DDR memory clocks with local radio module frequency bands used
>> by Wifi 6/6e/7.
>>
>> To mitigate this, AMD has introduced an ACPI based mechanism that
>> devices can use to notify active use of particular frequencies so
>> that devices can make relative internal adjustments as necessary
>> to avoid this resonance.
>>
>> In order for a device to support this, the expected flow for device
>> driver or subsystems:
>>
>> Drivers/subsystems contributing frequencies:
>>
>> 1) During probe, check `wbrf_supported_producer` to see if WBRF supported
> The prefix should be acpi_wbrf_ or acpi_amd_wbrf_ even, so it is clear
> that this uses ACPI and is AMD-specific.

I guess if we end up with an intermediary library approach
wbrf_supported_producer makes sense and that could call acpi_wbrf_*.

But with no intermediate library your suggestion makes sense.

I would prefer not to make it acpi_amd as there is no reason that
this exact same problem couldn't happen on an
Wifi 6e + Intel SOC + AMD dGPU design too and OEMs could use the
same mitigation mechanism as Wifi6e + AMD SOC + AMD dGPU too.

>
> Whether or not there needs to be an intermediate library wrapped
> around this is a different matter.