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 8E6E6C433EF for ; Mon, 7 Feb 2022 07:12:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230510AbiBGHLC (ORCPT ); Mon, 7 Feb 2022 02:11:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50624 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244462AbiBGHD5 (ORCPT ); Mon, 7 Feb 2022 02:03:57 -0500 X-Greylist: delayed 556 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Sun, 06 Feb 2022 23:03:56 PST Received: from muru.com (muru.com [72.249.23.125]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D5910C0401C0; Sun, 6 Feb 2022 23:03:56 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by muru.com (Postfix) with ESMTPS id 4FDBE80E1; Mon, 7 Feb 2022 06:54:16 +0000 (UTC) Date: Mon, 7 Feb 2022 08:54:37 +0200 From: Tony Lindgren To: Nishanth Menon Cc: Matthias Schiffer , Rob Herring , Arnd Bergmann , Olof Johansson , soc@kernel.org, Vignesh Raghavendra , Tero Kristo , jan.kiszka@siemens.com, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] arm64: dts: ti: k3-am65: disable optional peripherals by default Message-ID: References: <20220203140240.973690-1-matthias.schiffer@ew.tq-group.com> <20220204143108.653qk2ihnlhsr5aa@prior> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220204143108.653qk2ihnlhsr5aa@prior> Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi, * Nishanth Menon [220204 14:30]: > Rob, Tony, Arnd, SoC maintainers, > > On 15:02-20220203, Matthias Schiffer wrote: > > All peripherals that require pinmuxing or other configuration to work > > should be disabled by default. Dependent DTS are adjusted accordingly. Disabling SoC internal devices by default is not a good policy. The devices are available even if not pinned out. Disabling device by default causes runtime PM to not work as the kernel will completely ignore the disabled devices. And this means you add a dependency to some certain version of a bootloader for PM to work. Additionally tagging devices as disabled by default (and then again re-enabling them in the board specific dts files) is just pointless churn and bloat. See for example commit 12afc0cf8121 ("ARM: dts: Drop pointless status changing for am3 musb") :) If you really want to disable some devices for memory usage or other reasons, do it in the board specific dts files. > https://lore.kernel.org/linux-arm-kernel/20201112183538.6805-1-nm@ti.com/ > reversal all over again. > > Is there a specific pattern we are intending to use here? Because, if we > are going down this path (which would be a major churn across multiple > downstream trees as well) - I'd rather have this as a documented > standard and not just a TI approach and will need to be done across all > K3 devices. > > Are you aware of such a documented guideline, rather than "word of > mouth"? Maybe I have'nt looked deep enough, but checking.. For SoCs that don't implement runtime PM the policy can be different without causing any harm. But for any SoCs implementing runtime PM, an unknown state from the bootloader is not going to work. Regards, Tony