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 smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2D9AAC433FE for ; Mon, 7 Feb 2022 11:25:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) id D5571C340F0; Mon, 7 Feb 2022 11:25:17 +0000 (UTC) Received: from muru.com (muru.com [72.249.23.125]) by smtp.kernel.org (Postfix) with ESMTP id B5AA4C340EB; Mon, 7 Feb 2022 11:25:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 smtp.kernel.org B5AA4C340EB Authentication-Results: smtp.kernel.org; dmarc=none (p=none dis=none) header.from=atomide.com Authentication-Results: smtp.kernel.org; spf=none smtp.mailfrom=atomide.com 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 List-Id: 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> * 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