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 C256BC46467 for ; Mon, 16 Jan 2023 17:23:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234641AbjAPRXP (ORCPT ); Mon, 16 Jan 2023 12:23:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46972 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234623AbjAPRWg (ORCPT ); Mon, 16 Jan 2023 12:22:36 -0500 Received: from muru.com (muru.com [72.249.23.125]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 449CE36FE9; Mon, 16 Jan 2023 09:00:32 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by muru.com (Postfix) with ESMTPS id AB5638108; Mon, 16 Jan 2023 17:00:31 +0000 (UTC) Date: Mon, 16 Jan 2023 19:00:30 +0200 From: Tony Lindgren To: "H. Nikolaus Schaller" Cc: Adam Ford , Andreas Kemnade , =?utf-8?Q?Beno=C3=AEt?= Cousson , robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, linux-omap@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ARM: dts: gta04: fix excess dma channel usage Message-ID: References: <20230113211151.2314874-1-andreas@kemnade.info> <4EFDE2C4-0BBB-4804-AA46-C40EB0D97AC4@goldelico.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4EFDE2C4-0BBB-4804-AA46-C40EB0D97AC4@goldelico.com> Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org * H. Nikolaus Schaller [230116 15:29]: > Hi, > > > Am 16.01.2023 um 15:51 schrieb Tony Lindgren : > > > > Hi, > > > > * Adam Ford [230116 14:16]: > >> Would it make sense to make this default in the omap3.dtsi file and > >> enable them in the individual boards that need it? > > > > In general disabling the unused devices by default for omaps will break > > the power management. The disabled devices are completely ignored by the > > kernel, and the devices are left to whatever the bootloader state might > > be. > > Yes, indeed. See my further clarification based on what Adam commented too, I was thinking status = "disabled" at the ti-sysc parent level. > > For SoCs using firmware to manage devices it's a bit different story > > however. The firmware can still idle disabled devices based on a > > late_initcall for example, even if the kernel knows nothing about the > > disabled devices. > > But how can we then handle all devices being "okay" by default and > eating up more dma channels than are available? 1. Set the child device (not the ti-sysc node) with status = "disabled" in the board specific file as needed 2. Use /delete-property/ for dma channels in the board specific file if the device is in use but does not need dma 3. Or if this is a generic problem, we could disable dma by default for some devices > We can't put all under power management AND dma by default. > > Or can dma channel usage be postponed until the device is really used? Sure. Regards, Tony