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 4EE60C433FE for ; Mon, 7 Feb 2022 12:16:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346771AbiBGMJy (ORCPT ); Mon, 7 Feb 2022 07:09:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357632AbiBGLZ0 (ORCPT ); Mon, 7 Feb 2022 06:25:26 -0500 Received: from muru.com (muru.com [72.249.23.125]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 943ECC03FED1; Mon, 7 Feb 2022 03:25:16 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by muru.com (Postfix) with ESMTPS id EB08280E1; Mon, 7 Feb 2022 11:24:52 +0000 (UTC) Date: Mon, 7 Feb 2022 13:25:14 +0200 From: Tony Lindgren To: Matthias Schiffer Cc: 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, Nishanth Menon 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> <5944ba0ce568eaf507917799b1dfd89a3d0ca492.camel@ew.tq-group.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5944ba0ce568eaf507917799b1dfd89a3d0ca492.camel@ew.tq-group.com> Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org * Matthias Schiffer [220207 08:45]: > Generally I think that it's a bootloader's responsiblity to disable > unneeded devices - the kernel may not even have a driver for some > peripherals, leading to the same behaviour as a "disabled" status. For > this reason I believe that it should always be okay to set unneeded > devices to "disabled", and it should be considered a safe default. Not possible, think kexec for example :) How would the previous kernel even know what to disable if Linux has no idea about the devices? If there are issues you're seeing, it's likely a bug in some of the device drivers for not checking for the necessary resources like pinctrl for i2c lines. > I'm not sure what the consensus on these issues is. I'm more familiar > with NXP's i.MX and Layerscape SoCs, where it's common to have all > muxable peripherals set to "disabled" in the base DTSI, and a quick > grep through a few dts directories gives me the impression that this is > the case for most other vendors as well. This approach only works for SoCs that don't need the kernel to idle devices for runtime PM. Regards, Tony