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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 F02A0C2D0E8 for ; Thu, 26 Mar 2020 14:23:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0E1B206F8 for ; Thu, 26 Mar 2020 14:23:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727991AbgCZOXw (ORCPT ); Thu, 26 Mar 2020 10:23:52 -0400 Received: from mga17.intel.com ([192.55.52.151]:20673 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727869AbgCZOXw (ORCPT ); Thu, 26 Mar 2020 10:23:52 -0400 IronPort-SDR: V0OKcmgpwP/pm9ybSEtswjlXlaHLMcFnWJ9I/r1d98RDV0rInFcCc8x8pwCSd7tSOVNYBBbVHe LJ1LkCADYgdQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Mar 2020 07:23:52 -0700 IronPort-SDR: DimBgg8sUOWeCGBgqUZj9R2clPDodmlm9rZiNKMrLL1pxw1LeFXbUuozHmbhQTCfV3CMJHQYBN K49CAPxNv3hw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,308,1580803200"; d="scan'208";a="265882920" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga002.jf.intel.com with ESMTP; 26 Mar 2020 07:23:48 -0700 Received: from andy by smile with local (Exim 4.93) (envelope-from ) id 1jHTQE-00D99J-Dv; Thu, 26 Mar 2020 16:23:50 +0200 Date: Thu, 26 Mar 2020 16:23:50 +0200 From: Andy Shevchenko To: Grant Likely Cc: Peter Ujfalusi , "Rafael J. Wysocki" , Saravana Kannan , Andrzej Hajda , Artem Bityutskiy , Felipe Balbi , Mark Brown , Ferry Toth , Greg Kroah-Hartman , LKML , Linux PM , Android Kernel Team , nd Subject: Re: [PATCH v3] driver core: Break infinite loop when deferred probe can't be satisfied Message-ID: <20200326142350.GW1922688@smile.fi.intel.com> References: <20200324175719.62496-1-andriy.shevchenko@linux.intel.com> <20200325032901.29551-1-saravanak@google.com> <20200325125120.GX1922688@smile.fi.intel.com> <20200326120323.GR1922688@smile.fi.intel.com> <6c04af00-adc8-6be2-b7fd-b4a875524563@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6c04af00-adc8-6be2-b7fd-b4a875524563@arm.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 26, 2020 at 01:45:50PM +0000, Grant Likely wrote: > On 26/03/2020 12:03, Andy Shevchenko wrote: > > On Thu, Mar 26, 2020 at 11:45:18AM +0200, Peter Ujfalusi wrote: > > > On 26/03/2020 10.39, Rafael J. Wysocki wrote: > > > > On Wed, Mar 25, 2020 at 11:09 PM Saravana Kannan wrote: > > > > > On Wed, Mar 25, 2020 at 5:51 AM Andy Shevchenko > > > > > wrote: > > > > ... > > > > > > OK, so the situation right now is that commit 58b116bce136 has > > > > introduced a regression and so it needs to be fixed or reverted. The > > > > cases that were previously broken and were unbroken by that commit > > > > don't matter here, so you cannot argue that they would be "broken". > > > > > > commit 58b116bce136 is from 2014 and the whole ULPI support for dwc3 > > > came in a year later. > > > While I agree that 58b116bce136 fail to handle came a year later, but > > > technically it did not introduced a regression. > > > > > > The revert on the other hand is going to introduce a regression as > > > things were working fine since 2014. Not sure why the dwc3 issue got > > > this long to be noticed as the 58b116bce136 was already in kernel when > > > the ULPI support was added... > > > > I dare to say that is luck based on people's laziness to figure out the root > > cause. As I pointed out in email to Saravana the issue is not limited to USB > > case and, if my memory doesn't trick me out, I suffered from it approximately > > in ~2014-2015 with pin control tables. > > I've not been involved in this for a very long time, but from our past > conversations and the description that is given here I still feel that this > problem is a design bug on the dwc3 driver dependencies rather than a > failure with driver core. dwc3 is doing something rather convoluted and it > would be worth reevaluating how probe failures are unwound on that > particular driver stack. I disagree. Have you chance to look into another example I gave to Saravana? The unbalanced increment is fragile per se, because you can't guarantee that it will be no unsynchronization between probed successfully (unrelated!) and deferred drivers. -- With Best Regards, Andy Shevchenko