From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregkh@linuxfoundation.org (Greg Kroah-Hartman) Date: Sat, 7 Jul 2018 17:59:21 +0200 Subject: [PATCH v2] driver core: add a debugfs entry to show deferred devices In-Reply-To: <20180627220656.19298-1-javierm@redhat.com> References: <20180627220656.19298-1-javierm@redhat.com> Message-ID: <20180707155921.GA26504@kroah.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jun 28, 2018 at 12:06:56AM +0200, Javier Martinez Canillas wrote: > With Device Trees (DT), the dependencies of the devices are defined in the > DT, then the drivers parse that information to lookup the needed resources > that have as dependencies. > > Since drivers and devices are registered in a non-deterministic way, it is > possible that a device that is a dependency has not been registered yet by > the time that is looked up. > > In this case the driver that requires this dependency cannot probe and has > to defer it. So the driver core adds it to a list of deferred devices that > is iterated again every time that a new driver is probed successfully. > > For debugging purposes it may be useful to know what are the devices whose > probe function was deferred. Add a debugfs entry showing that information. > > $ cat /sys/kernel/debug/devices_deferred > 48070000.i2c:twl at 48:bci > musb-hdrc.0.auto > omapdrm.0 > > This information could be obtained partially by enabling debugging, but it > means that the kernel log has to be parsed and the probe deferral balanced > with the successes. This can be error probe and has to be done in a ad-hoc > manner by everyone who needs to debug these kind of issues. > > Since the information is already known by the kernel, just show it to make > it easier to debug. > > Signed-off-by: Javier Martinez Canillas > Reviewed-by: Mark Brown This doesn't apply to my tree anymore :( Can you rebase and resend? thanks, greg k-h 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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 B5F0AC6778A for ; Sat, 7 Jul 2018 15:59:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6EA7B216F8 for ; Sat, 7 Jul 2018 15:59:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6EA7B216F8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754158AbeGGP71 (ORCPT ); Sat, 7 Jul 2018 11:59:27 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:56404 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753572AbeGGP70 (ORCPT ); Sat, 7 Jul 2018 11:59:26 -0400 Received: from localhost (unknown [37.168.185.56]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 0EACADBB; Sat, 7 Jul 2018 15:59:24 +0000 (UTC) Date: Sat, 7 Jul 2018 17:59:21 +0200 From: Greg Kroah-Hartman To: Javier Martinez Canillas Cc: linux-kernel@vger.kernel.org, Tomeu Vizoso , Rob Herring , Mark Brown , Andy Shevchenko , Peter Robinson , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2] driver core: add a debugfs entry to show deferred devices Message-ID: <20180707155921.GA26504@kroah.com> References: <20180627220656.19298-1-javierm@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180627220656.19298-1-javierm@redhat.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 28, 2018 at 12:06:56AM +0200, Javier Martinez Canillas wrote: > With Device Trees (DT), the dependencies of the devices are defined in the > DT, then the drivers parse that information to lookup the needed resources > that have as dependencies. > > Since drivers and devices are registered in a non-deterministic way, it is > possible that a device that is a dependency has not been registered yet by > the time that is looked up. > > In this case the driver that requires this dependency cannot probe and has > to defer it. So the driver core adds it to a list of deferred devices that > is iterated again every time that a new driver is probed successfully. > > For debugging purposes it may be useful to know what are the devices whose > probe function was deferred. Add a debugfs entry showing that information. > > $ cat /sys/kernel/debug/devices_deferred > 48070000.i2c:twl@48:bci > musb-hdrc.0.auto > omapdrm.0 > > This information could be obtained partially by enabling debugging, but it > means that the kernel log has to be parsed and the probe deferral balanced > with the successes. This can be error probe and has to be done in a ad-hoc > manner by everyone who needs to debug these kind of issues. > > Since the information is already known by the kernel, just show it to make > it easier to debug. > > Signed-off-by: Javier Martinez Canillas > Reviewed-by: Mark Brown This doesn't apply to my tree anymore :( Can you rebase and resend? thanks, greg k-h