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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 1635BC282DC for ; Sun, 2 Jun 2019 23:24:57 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3AF6A27A0C for ; Sun, 2 Jun 2019 23:24:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3AF6A27A0C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 45HDmj37XszDqMl for ; Mon, 3 Jun 2019 09:24:53 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=permerror (mailfrom) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 45HDlM60fFzDqMb for ; Mon, 3 Jun 2019 09:23:43 +1000 (AEST) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id x52NNW8Z013902; Sun, 2 Jun 2019 18:23:33 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id x52NNU3p013901; Sun, 2 Jun 2019 18:23:30 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Sun, 2 Jun 2019 18:23:30 -0500 From: Segher Boessenkool To: Benjamin Herrenschmidt Subject: Re: [PATCH kernel] prom_init: Fetch flatten device tree from the system firmware Message-ID: <20190602232330.GN31586@gate.crashing.org> References: <20190501034221.18437-1-aik@ozlabs.ru> <20190530193736.GC31586@gate.crashing.org> <43f037c57eed8ad2175470c940917dced947bb70.camel@kernel.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43f037c57eed8ad2175470c940917dced947bb70.camel@kernel.crashing.org> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , linuxppc-dev@lists.ozlabs.org, Suraj Jitindar Singh , David Gibson Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi! On Fri, May 31, 2019 at 11:03:26AM +1000, Benjamin Herrenschmidt wrote: > On Thu, 2019-05-30 at 14:37 -0500, Segher Boessenkool wrote: > > On Thu, May 30, 2019 at 05:09:06PM +1000, Alexey Kardashevskiy wrote: > > > so, it is sort-of nack from David and sort-of ack from Segher, what > > > happens now? > > > > Maybe what we really need just a CI call to get all properties of a node > > at once? Will that speed up things enough? > > > > That way you need no change at all in lifetime of properties and how they > > are used, etc.; just a client getting the properties is a lot faster. > > Hrm... if we're going to create a new interface, let's go for what we > need. > > What we need is the FDT. It's a rather ubiquitous thing these days, it > makes sense to have a way to fetch an FDT directly from FW. That is all you need if you do not want to use OF at all. If you *do* want to keep having an Open Firmware, what we want or need is a faster way to walk huge device trees. > There is no use for the "fetch all properties" cases other than > building an FDT that any of us can think of, and it would create a more > complicated interface than just "fetch an FDT". It is a simple way to speed up fetching the device tree enormously, without needing big changes to either OF or the clients using it -- not in the code, but importantly also not conceptually: everything works just as before, just a lot faster. > So I go for the simple one and agree with Alexey's idea. When dealing with a whole device tree you have to know about the various dynamically generated nodes and props, and handle each appropriately. Segher