From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756471AbbJUVus (ORCPT ); Wed, 21 Oct 2015 17:50:48 -0400 Received: from mail-pa0-f66.google.com ([209.85.220.66]:36795 "EHLO mail-pa0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756234AbbJUVun (ORCPT ); Wed, 21 Oct 2015 17:50:43 -0400 Message-ID: <562808AF.7090406@gmail.com> Date: Wed, 21 Oct 2015 14:50:39 -0700 From: Frank Rowand Reply-To: frowand.list@gmail.com User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Rob Herring CC: Mark Brown , Tomeu Vizoso , Greg Kroah-Hartman , Russell King , Michael Turquette , Stephen Boyd , Vinod Koul , Dan Williams , Linus Walleij , Alexandre Courbot , Thierry Reding , David Airlie , =?UTF-8?B?VGVyamUgQmVyZ3N0csO2bQ==?= , Stephen Warren , Wolfram Sang , Grant Likely , Kishon Vijay Abraham I , Sebastian Reichel , Dmitry Eremin-Solenikov , David Woodhouse , Liam Girdwood , Felipe Balbi , Jingoo Han , Lee Jones , Jean-Christophe Plagniol-Villard , Tomi Valkeinen , "linux-kernel@vger.kernel.org" , linux-clk@vger.kernel.org, dmaengine@vger.kernel.org, "linux-gpio@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linux-tegra@vger.kernel.org" , "linux-i2c@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-pm@vger.kernel.org" , Linux PWM List , "linux-usb@vger.kernel.org" , "linux-fbdev@vger.kernel.org" Subject: Re: [GIT PULL] On-demand device probing References: <561E1378.6000906@collabora.com> <20151017065750.GA18607@kroah.com> <20151018192931.GY14956@sirena.org.uk> <20151018193757.GA9147@kroah.com> <20151018195330.GB14956@sirena.org.uk> <5627B677.5090109@gmail.com> <20151021162758.GP32054@sirena.org.uk> <5627D6E0.5020708@gmail.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/21/2015 2:12 PM, Rob Herring wrote: > On Wed, Oct 21, 2015 at 1:18 PM, Frank Rowand wrote: >> On 10/21/2015 9:27 AM, Mark Brown wrote: >>> On Wed, Oct 21, 2015 at 08:59:51AM -0700, Frank Rowand wrote: >>>> On 10/19/2015 5:34 AM, Tomeu Vizoso wrote: >>> >>>>> To be clear, I was saying that this series should NOT affect total >>>>> boot times much. >>> >>>> I'm confused. If I understood correctly, improving boot time was >>>> the key justification for accepting this patch set. For example, >>>> from "[PATCH v7 0/20] On-demand device probing": >>>> >>>> I have a problem with the panel on my Tegra Chromebook taking longer >>>> than expected to be ready during boot (Stéphane Marchesin reported what >>>> is basically the same issue in [0]), and have looked into ordered >>>> probing as a better way of solving this than moving nodes around in the >>>> DT or playing with initcall levels and linking order. >>>> >>>> ... >>>> >>>> With this series I get the kernel to output to the panel in 0.5s, >>>> instead of 2.8s. >>> >>> Overall boot time and time to get some individual built in component up >>> and running aren't the same thing - what this'll do is get things up >>> more in the link order of the leaf consumers rather than deferring those >>> leaf consumers when their dependencies aren't ready yet. >> >> Thanks! I read too much into what was being improved. >> >> So this patch series, which on other merits may be a good idea, is as >> a by product solving a specific ordering issue, moving successful panel >> initialization to an earlier point in the boot sequence, if I now >> understand more correctly. >> >> In that context, this seems like yet another ad hoc way of causing the >> probe order to change in a way to solves one specific issue? Could >> it just as likely move the boot order of some other driver on some >> other board later, to the detriment of somebody else? > > Time to display on is important for many products. Having the console > up as early as possible is another case. CAN bus is another. This is a > real problem that is not just bad drivers. Yes, I agree. What I am seeing is that there continues to be a need for the ability to explicitly order at least some driver initialization (at some granularity), despite the push back against explicit ordering that has been present in the past. > I don't think it is completely ad hoc. Given all devices are > registered after drivers, drivers will still probe first in initcall > level order and then link order AFAIK. We may not take (more) initcall > level tweak hacks, but that is a much more simple change for > downstream. Don't get me wrong, I'd really like to see a way to > control order independent of initcall level. > > Rob Yep, it is not directly ad hoc, just a fortunate side effect in this case. So just accidently ad hoc. :-) -Frank