From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753054Ab2A3Rt2 (ORCPT ); Mon, 30 Jan 2012 12:49:28 -0500 Received: from mho-02-ewr.mailhop.org ([204.13.248.72]:45539 "EHLO mho-02-ewr.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752197Ab2A3Rt1 (ORCPT ); Mon, 30 Jan 2012 12:49:27 -0500 X-Mail-Handler: MailHop Outbound by DynDNS X-Originating-IP: 98.234.237.12 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/mailhop/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX1/5OhLiSH8XyasiXC80ln3O Date: Mon, 30 Jan 2012 09:49:10 -0800 From: Tony Lindgren To: Shawn Guo Cc: Simon Glass , Stephen Warren , Dong Aisheng-B29396 , "Linus Walleij (linus.walleij@linaro.org)" , "Sascha Hauer (s.hauer@pengutronix.de)" , "rob.herring@calxeda.com" , "kernel@pengutronix.de" , "cjb@laptop.org" , Dong Aisheng , Thomas Abraham , "Grant Likely (grant.likely@secretlab.ca)" , "devicetree-discuss@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: Pinmux bindings proposal V2 Message-ID: <20120130174910.GG9339@atomide.com> References: <74CDBE0F657A3D45AFBB94109FB122FF1780DAB4CE@HQMAIL01.nvidia.com> <20120127022111.GK29812@atomide.com> <20120130031346.GD10470@S2101-09.ap.freescale.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120130031346.GD10470@S2101-09.ap.freescale.net> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Shawn Guo [120129 18:30]: > On Fri, Jan 27, 2012 at 07:43:36AM -0800, Simon Glass wrote: > ... > > The cost of the pmx@dta node is about 12 bytes for the header (it > > depends on the length of the name), and each of the properties above > > is 16 bytes. So in total this node is 76 bytes. If we have 250 pins > > being muxed as Tegra3 then this is about 20KB (including a bit of > > slack for longer names). My point about being able to 'optimise out' > > some of these remains, though, but probably not for the kernel. > > > > Stephen's 'mux' property uses 12 bytes plus 8 bytes per pin/group (I > > am removing the prefixes): > > > > mux = > > > > ; > > > > so 28 bytes. What I proposed would use (12 + 2 * 16) per pin/group, or > > 44 bytes (60% bigger): > > > It's not only about size but also run-time tree travelling efficiency. > Your proposal requires every single pin show as a node in device tree. > Looking at these for_each_node_by_*() APIs in include/linux/of.h, you > might agree we should avoid bloating device tree with so many nodes. And that's why I'm suggesting two bindings: A minimal pinctrl-static binding and more verbose pinctrl-dynamic binding. AFAIK the number of pinctrl-dynamic bindings needed are just a fraction of the pinctrl-static bindings. So the extra parsing needed for a few pinctrl-dynamic bindings should not matter. Sure it would be nice to have it all in a single binding, but these bindings have conflicting requirements. So it may not be possible to do it in a single binding in an efficient way. Regards, Tony