From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43BF9EB64D7 for ; Wed, 21 Jun 2023 16:52:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230004AbjFUQw5 (ORCPT ); Wed, 21 Jun 2023 12:52:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229544AbjFUQwz (ORCPT ); Wed, 21 Jun 2023 12:52:55 -0400 Received: from vps0.lunn.ch (vps0.lunn.ch [156.67.10.101]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7BF22E9; Wed, 21 Jun 2023 09:52:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:From:Sender:Reply-To:Subject: Date:Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Content-Disposition:In-Reply-To:References; bh=6WA3GXEESmxypvEyfFrL5uv4yC5/yc2PeWiHyP0/kFg=; b=jAR7VSWfsOiZvPQRWvfZ2NZjiN u8ceeRk9ZsuwLMn8AlYC16evp29iYpzUudOF2rR7oo3CoOh8zWOqvZG3DjtQNIYhFAW1zHzuRA64i gX6Kh0SKw1KNU3J/dr5DyzRnlVR4WWysO8U1/IS/P5ISI66I9bNN7tjCYnXCBsRK926o=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1qC148-00HAOG-F0; Wed, 21 Jun 2023 18:52:20 +0200 Date: Wed, 21 Jun 2023 18:52:20 +0200 From: Andrew Lunn To: "Limonciello, Mario" Cc: Johannes Berg , Evan Quan , rafael@kernel.org, lenb@kernel.org, alexander.deucher@amd.com, christian.koenig@amd.com, Xinhui.Pan@amd.com, airlied@gmail.com, daniel@ffwll.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, mdaenzer@redhat.com, maarten.lankhorst@linux.intel.com, tzimmermann@suse.de, hdegoede@redhat.com, jingyuwang_vip@163.com, lijo.lazar@amd.com, jim.cromie@gmail.com, bellosilicio@gmail.com, andrealmeid@igalia.com, trix@redhat.com, jsg@jsg.id.au, arnd@arndb.de, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH V4 1/8] drivers/acpi: Add support for Wifi band RF mitigations Message-ID: <36902dda-9e51-41b3-b5fc-c641edf6f1fb@lunn.ch> References: <20230621054603.1262299-1-evan.quan@amd.com> <20230621054603.1262299-2-evan.quan@amd.com> <3a7c8ffa-de43-4795-ae76-5cd9b00c52b5@lunn.ch> <216f3c5aa1299100a0009ddf4e95b019855a32be.camel@sipsolutions.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Wed, Jun 21, 2023 at 11:15:00AM -0500, Limonciello, Mario wrote: > > On 6/21/2023 10:39 AM, Johannes Berg wrote: > > On Wed, 2023-06-21 at 17:36 +0200, Andrew Lunn wrote: > > > On Wed, Jun 21, 2023 at 01:45:56PM +0800, Evan Quan wrote: > > > > From: Mario Limonciello > > > > > > > > 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? > > They could, of course, but they'd need some other driver to change > > _something_ in the system? I don't even know what this is doing > > precisely under the hood in the ACPI BIOS, perhaps it adjusts the DDR > > memory clock frequency in response to WiFi using a frequency that will > > cause interference with harmonics. > > The way that WBRF has been architected, it's intended to be able > to scale to any type of device pair that has harmonic issues. So you set out to make something generic... > In the first use (Wifi 6e + specific AMD dGPUs) that matches this > series BIOS has the following purposes: > > 1) The existence of _DSM indicates that the system may not have > adequate shielding and should be using these mitigations. > > 2) Notification mechanism of frequency use. > > For the first problematic devices we *could* have done notifications > entirely in native Linux kernel code with notifier chains. > However that still means you need a hint from the platform that the > functionality is needed like a _DSD bit. > > It's also done this way so that AML could do some of the notifications > directly to applicable devices in the future without needing "consumer" > driver participation. And then tie is very closely to ACPI. Now, you are AMD, i get that ACPI is what you have. But i think as kernel Maintainers, we need to consider that ACPI is not the only thing used. Do we want the APIs to be agnostic? I think APIs used by drivers should be agnostic. Andrew