linux-kernel - RE: [V10 1/8] ACPI: Add support for AMD ACPI based Wifi band RFI mitigation feature

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Message-ID: <DM6PR12MB2619013F8683DFBBADC68502E4E0A@DM6PR12MB2619.namprd12.prod.outlook.com>
Date:   Mon, 28 Aug 2023 02:11:27 +0000
From:   "Quan, Evan" <Evan.Quan@....com>
To:     Simon Horman <horms@...nel.org>
CC:     "lenb@...nel.org" <lenb@...nel.org>,
        "johannes@...solutions.net" <johannes@...solutions.net>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "Lazar, Lijo" <Lijo.Lazar@....com>,
        "Limonciello, Mario" <Mario.Limonciello@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [V10 1/8] ACPI: Add support for AMD ACPI based Wifi band RFI
 mitigation feature

[AMD Official Use Only - General]

> -----Original Message-----
> From: Simon Horman <horms@...nel.org>
> Sent: Sunday, August 27, 2023 11:43 PM
> To: Quan, Evan <Evan.Quan@....com>
> Cc: lenb@...nel.org; johannes@...solutions.net; davem@...emloft.net;
> edumazet@...gle.com; kuba@...nel.org; pabeni@...hat.com; Deucher,
> Alexander <Alexander.Deucher@....com>; rafael@...nel.org; Lazar, Lijo
> <Lijo.Lazar@....com>; Limonciello, Mario <Mario.Limonciello@....com>;
> 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: [V10 1/8] ACPI: Add support for AMD ACPI based Wifi band RFI
> mitigation feature
>
> On Fri, Aug 25, 2023 at 04:38:39PM +0800, Evan Quan wrote:
> > 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 a mechanism that devices can use
> > to notify active use of particular frequencies so that other devices
> > can make relative internal adjustments as necessary to avoid this resonance.
> >
> > Signed-off-by: Evan Quan <evan.quan@....com>
>
> ...
>
> > diff --git a/drivers/acpi/amd_wbrf.c b/drivers/acpi/amd_wbrf.c
>
> ...
>
> > +/**
> > + * acpi_amd_wbrf_add_exclusion - broadcast the frequency band the
> device
> > + *                               is using
> > + *
> > + * @dev: device pointer
> > + * @in: input structure containing the frequency band the device is
> > +using
> > + *
> > + * Broadcast to other consumers the frequency band the device starts
> > + * to use. Underneath the surface the information is cached into an
> > + * internal buffer first. Then a notification is sent to all those
> > + * registered consumers. So then they can retrieve that buffer to
> > + * know the latest active frequency bands. The benifit with such
> > +design
>
> nit: ./checkpatch.pl --codespell suggests benifit -> benefit.
Thanks, will fix that.

Evan
>
> > + * is for those consumers which have not been registered yet, they
> > +can
> > + * still have a chance to retrieve such information later.
> > + */
> > +int acpi_amd_wbrf_add_exclusion(struct device *dev,
> > +                           struct wbrf_ranges_in_out *in)
> > +{
> > +   struct acpi_device *adev = ACPI_COMPANION(dev);
> > +   int ret;
> > +
> > +   if (!adev)
> > +           return -ENODEV;
> > +
> > +   ret = wbrf_record(adev, WBRF_RECORD_ADD, in);
> > +   if (ret)
> > +           return ret;
> > +
> > +   blocking_notifier_call_chain(&wbrf_chain_head,
> > +                                WBRF_CHANGED,
> > +                                NULL);
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_amd_wbrf_add_exclusion);
>
> ...