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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A699CC48BD6 for ; Thu, 27 Jun 2019 10:58:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7CE642086D for ; Thu, 27 Jun 2019 10:58:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561633107; bh=eqIMm2IvCi/2kqSke0jwsbTzK/3H02BMhTr01hNqdt8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=ZOITUfqYUa2eRVCje1IiT1h1qjpBrz0Wui48dK3DMfFVLnpVWEZxhE783oTdoKXA3 ToH+EYhBnPXQVqBBmAHE6Yq2ASE1hmSbf/sNwJQN9yLo2L1VaHm9yXi1fXr5uEQEJg 7eZ/yxc3mdofaAezQktGb/jbf7DDb8YfXkz4O0mU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726628AbfF0K60 (ORCPT ); Thu, 27 Jun 2019 06:58:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:40182 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726315AbfF0K6Z (ORCPT ); Thu, 27 Jun 2019 06:58:25 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1F4F32085A; Thu, 27 Jun 2019 10:58:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561633104; bh=eqIMm2IvCi/2kqSke0jwsbTzK/3H02BMhTr01hNqdt8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=iauW/gb5jLquigQ+Cdzh/i9Pn3zW17VkPlONdHo7xFd7dA32bVmDJ/Yyb0bkTe8EG kIrY8RkURU97+7yoOa31J72E27OcFr0fIRUwyB35ALlHqV0dmT8JKXqUb21IVMoo+X l5U9Ro8xIQgWHOpJmZaP0lAAll1CxzuY2yED7AZg= Date: Thu, 27 Jun 2019 19:58:17 +0900 From: Masami Hiramatsu To: Rob Herring Cc: Steven Rostedt , Frank Rowand , Tom Zanussi , Ingo Molnar , Namhyung Kim , Jiri Olsa , Arnaldo Carvalho de Melo , "linux-kernel@vger.kernel.org" , devicetree@vger.kernel.org Subject: Re: [RFC PATCH 00/11] tracing: of: Boot time tracing using devicetree Message-Id: <20190627195817.211ab4bea422f37e539e47e8@kernel.org> In-Reply-To: References: <156113387975.28344.16009584175308192243.stgit@devnote2> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Rob, On Wed, 26 Jun 2019 15:58:50 -0600 Rob Herring wrote: > On Fri, Jun 21, 2019 at 10:18 AM Masami Hiramatsu wrote: > > > > Hi, > > > > Here is an RFC series of patches to add boot-time tracing using > > devicetree. > > > > Currently, kernel support boot-time tracing using kernel command-line > > parameters. But that is very limited because of limited expressions > > and limited length of command line. Recently, useful features like > > histogram, synthetic events, etc. are being added to ftrace, but it is > > clear that we can not expand command-line options to support these > > features. > > > > Hoever, I've found that there is a devicetree which can pass more > > structured commands to kernel at boot time :) The devicetree is usually > > used for dscribing hardware configuration, but I think we can expand it > > for software configuration too (e.g. AOSP and OPTEE already introduced > > firmware node.) Also, grub and qemu already supports loading devicetree, > > so we can use it not only on embedded devices but also on x86 PC too. > > Do the x86 versions of grub, qemu, EFI, any other bootloader actually > enable DT support? I didn't think so. Certainly, an x86 kernel doesn't > normally (other than OLPC and ce4100) have a defined way to even pass > a dtb from the bootloader to the kernel and the kernel doesn't > unflatten the dtb. Sorry, the grub part, I just found this entry. I need to check this can work on x86 too. https://www.gnu.org/software/grub/manual/grub/html_node/devicetree.html Anyway, I've tested this series on qemu-x86 with --dtb option. The kernel boot with ACPI and DT (hardware drivers seem initialized by ACPI), and it seems unflatten the dtb correctly. > > For arm64, the bootloader to kernel interface is DT even for ACPI > based systems. So unlike Frank, I'm not completely against DT being > the interface, but it's hardly universal across architectures and > something like this should be. Neither making DT the universal kernel > boot interface nor creating some new channel as Frank suggested seems > like an easy task. I don't want it making this for all architectures but an option for architecutres which supports DT already... Thank you, > > Rob -- Masami Hiramatsu