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 autolearn=no 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 54EABC33C99 for ; Sun, 5 Jan 2020 18:28:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25BE921734 for ; Sun, 5 Jan 2020 18:28:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578248913; bh=4x9vC91olmd60ycX0+AK25GUmB4k/f+cxqTH4tCuww8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=wJ6YHr2AhPGjwlGC5RINNE1YI0VWf/onJu6R+FyTMNHPXOqqgknpxhJTG/+nUxMum 0LIsJDLkUXdd06DgEx0vT6gcc/A+TlZPYPARO7ZZB3PC1xoYMQdIkEd75wlKaze+J/ gHkfeQcgA9dRm3jlSM5iSNh4UQr3UyaWnf+ptElE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726401AbgAES2a (ORCPT ); Sun, 5 Jan 2020 13:28:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:45592 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726368AbgAES2a (ORCPT ); Sun, 5 Jan 2020 13:28:30 -0500 Received: from localhost (lfbn-tou-1-1502-76.w90-89.abo.wanadoo.fr [90.89.68.76]) (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 AF62720866; Sun, 5 Jan 2020 18:28:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578248909; bh=4x9vC91olmd60ycX0+AK25GUmB4k/f+cxqTH4tCuww8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ExslCVI9aoGZEoasCewn+2z26EUJkgrLLXM4mFo8p8VKKO7R4I9kE/qBe2X93uG7+ 0bJdwQHlBwBT4aWDlPxzeDFTmH9rYUI0dEUnKrqJpPnb7WMtNDTnVhzLw4bSjv80gp bAcvqQfIGqLI7Rr/sj2DMWDyXkPLl41LK1Aghwio= Date: Sun, 5 Jan 2020 19:28:26 +0100 From: Maxime Ripard To: =?utf-8?B?QW5kcsOp?= Przywara Cc: Chen-Yu Tsai , Mark Rutland , Rob Herring , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com, Icenowy Zheng Subject: Re: [PATCH 3/3] ARM: dts: sun8i: R40: Add SPI controllers nodes and pinmuxes Message-ID: <20200105182826.rnscz5d5pbtb72g2@gilmour.lan> References: <20200102012657.9278-1-andre.przywara@arm.com> <20200102012657.9278-4-andre.przywara@arm.com> <20200102095711.dkd2cnbyitz6mvyx@gilmour.lan> <20200102104158.06d9baa0@donnerap.cambridge.arm.com> <20200104100422.z7iz4jiyj7kdvbtw@gilmour.lan> <42aabc62-4885-38fc-a6e5-0f057843d364@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <42aabc62-4885-38fc-a6e5-0f057843d364@arm.com> Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Sun, Jan 05, 2020 at 04:40:58PM +0000, Andr=E9 Przywara wrote: > On 04/01/2020 10:04, Maxime Ripard wrote: > >> But more importantly: what are the guidelines for using this tag? I > >> understand the desire to provide every possible pin description on > >> one hand, but wanting to avoid having *all of them* in *each* .dtb > >> on the other. > > > > Pin groups will take a lot of space in the dtb, and the DT parsing > > will take some measurable time, > > Really? Where is that? In Linux, or in U-Boot, possibly with the caches > off? I am just curious. AFAIK there are some inefficient algorithms in > libfdt (which trade performance for a smaller memory footprint), but I > thought those would be called only very rarely. The last time I measured it was in U-Boot (and for the FIT image, not an actual DT), but the parsing time for a FIT image with a kernel and DTB was around 100ms. (and adding the PSCI and simplefb nodes was in the same order of magnitude). Boot time was very sensitive, and I had to remove both. > >> And should there be a dtc command line option to ignore those tags, > >> or even to apply this tag (virtually) to every node? > > > > Most of the nodes are (reference) leaves in a DT though. Pretty much > > all the device nodes have no references pointing to them, just like > > most of the buses, the CPU nodes, etc. And I'm pretty sure you want to > > keep them :) > > Yeah, that was a New-Year's brain-fart of mine ;-) > > While I was changing the patch I figured that it gets quite lengthy. > Also looking at the a20.dtsi, I see that *all* pin groups have this tag > now. Wouldn't it be easier to introduce *one* tag that applies that to > all children of a node? I don't really know, I'm not sure the proliferation of tags would be a good thing either, and I'm not the dtc maintainer, so I don't really have a say in this :) > Another thing I was wondering about: Would we gain something by not > compiling nodes which have status =3D "disabled"? This is mentioned as a > generic property in the DT spec, although it says there that the exact > meaning is device dependent. But it sound still worthwhile, especially > since we would avoid more pin groups to be compiled in. I guess that would be good too, but the semantics are a bit different so we'd need a different tag. Maxime