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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 7EB5CC433E2 for ; Mon, 7 Sep 2020 12:04:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D835207C3 for ; Mon, 7 Sep 2020 12:04:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729019AbgIGMEE (ORCPT ); Mon, 7 Sep 2020 08:04:04 -0400 Received: from mga07.intel.com ([134.134.136.100]:17281 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729109AbgIGMDq (ORCPT ); Mon, 7 Sep 2020 08:03:46 -0400 IronPort-SDR: 3qH6NSllJxu3e7cU17CviuWtiOFNA/zyF9VJ37Zxu9dXKM6Av/FVX5lH3znZJ8Eoug1S8vfmJw /EDcGpCrL8NA== X-IronPort-AV: E=McAfee;i="6000,8403,9736"; a="222202391" X-IronPort-AV: E=Sophos;i="5.76,401,1592895600"; d="scan'208";a="222202391" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Sep 2020 05:03:00 -0700 IronPort-SDR: xAubLeS51761V1WF9ekhxvU4TOkUaH5XtH2RCHqvUVr3UfH05Jpsmv5yicd6P2gfWuPpx4nH3A 5lJ+RzQcoFsQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,401,1592895600"; d="scan'208";a="406817844" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.163]) by fmsmga001.fm.intel.com with SMTP; 07 Sep 2020 05:02:57 -0700 Received: by lahna (sSMTP sendmail emulation); Mon, 07 Sep 2020 15:02:56 +0300 Date: Mon, 7 Sep 2020 15:02:56 +0300 From: Mika Westerberg To: Lukas Wunner Cc: linux-usb@vger.kernel.org, Michael Jamet , Yehezkel Bernat , Andreas Noever , Kai-Heng Feng Subject: Re: [PATCH] thunderbolt: Retry DROM read once if parsing fails Message-ID: <20200907120256.GL2495@lahna.fi.intel.com> References: <20200907110340.71031-1-mika.westerberg@linux.intel.com> <20200907112151.GA22115@wunner.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200907112151.GA22115@wunner.de> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Mon, Sep 07, 2020 at 01:21:51PM +0200, Lukas Wunner wrote: > On Mon, Sep 07, 2020 at 02:03:40PM +0300, Mika Westerberg wrote: > > Kai-Heng reported that sometimes DROM parsing of ASUS PA27AC Thunderbolt 3 > > monitor fails. This makes the driver to fail to add the device so only > > DisplayPort tunneling is functional. > > Maybe the DROM is contained in an external EEPROM attached via slow > SPI or i2c and cannot be read in time before a response on the control > channel is due? Does it help to always delay 100 ms before performing > the DROM read with this display? Perhaps a quirk specific for this > display is more appropriate than a change which affects all devices? > Because this way of working around problems is difficult to maintain > long term. It helps to always wait the 100ms IIRC but I'm not sure we want to do that for every device. Also I'm not a fan of maintaining a list of quirks if we have the possibility to have more "general" solution to the issue (like what we do here, retry once).