linux-kernel - Re: [PATCH V4 1/8] drivers/acpi: Add support for Wifi band RF mitigations

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Message-ID: <3a7c8ffa-de43-4795-ae76-5cd9b00c52b5@lunn.ch>
Date:   Wed, 21 Jun 2023 17:36:17 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Evan Quan <evan.quan@....com>
Cc:     rafael@...nel.org, lenb@...nel.org, alexander.deucher@....com,
        christian.koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
        daniel@...ll.ch, johannes@...solutions.net, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        mario.limonciello@....com, mdaenzer@...hat.com,
        maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de,
        hdegoede@...hat.com, jingyuwang_vip@....com, lijo.lazar@....com,
        jim.cromie@...il.com, bellosilicio@...il.com,
        andrealmeid@...lia.com, trix@...hat.com, jsg@....id.au,
        arnd@...db.de, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH V4 1/8] drivers/acpi: Add support for Wifi band RF
 mitigations

On Wed, Jun 21, 2023 at 01:45:56PM +0800, Evan Quan wrote:
> From: Mario Limonciello <mario.limonciello@....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.

Do only ACPI based systems have:

   interference of relatively high-powered harmonics of the (G-)DDR
   memory clocks with local radio module frequency bands used by
   Wifi 6/6e/7."

Could Device Tree based systems not experience this problem?

> +/**
> + * APIs needed by drivers/subsystems for contributing frequencies:
> + * During probe, check `wbrf_supported_producer` to see if WBRF is supported.
> + * If adding frequencies, then call `wbrf_add_exclusion` with the
> + * start and end points specified for the frequency ranges added.
> + * If removing frequencies, then call `wbrf_remove_exclusion` with
> + * start and end points specified for the frequency ranges added.
> + */
> +bool wbrf_supported_producer(struct acpi_device *adev);
> +int wbrf_add_exclusion(struct acpi_device *adev,
> +		       struct wbrf_ranges_in *in);
> +int wbrf_remove_exclusion(struct acpi_device *adev,
> +			  struct wbrf_ranges_in *in);

Could struct device be used here, to make the API agnostic to where
the information is coming from? That would then allow somebody in the
future to implement a device tree based information provider.

       Andrew