From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Nikula Subject: Re: [PATCH] i2c: designware: Fix failure on baytrail Date: Tue, 13 Feb 2018 16:35:50 +0200 Message-ID: References: <1518113569-19991-1-git-send-email-gardner.ben@gmail.com> <945d4119-5aaf-520f-de2c-a9293f236f13@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mga04.intel.com ([192.55.52.120]:54884 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933651AbeBMOfa (ORCPT ); Tue, 13 Feb 2018 09:35:30 -0500 In-Reply-To: Content-Language: en-US Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Ben Gardner Cc: Linux I2C , Andy Shevchenko , Mika Westerberg Hi On 02/09/2018 05:07 PM, Ben Gardner wrote: > I bisected the kernel to try to find where this broke, but the answer > I kept on getting didn't make any sense. > I think t was this commit: > > 4d6d5f1d08d2138dc43b28966eb6200e3db2e623 i2c: designware: fix rx fifo > depth tracking > > Of course, reverting that one commit didn't fix anything. > So I added a log to the dw_readl() and dw_writel() functions in both a > working and broken kernel and compared. > Yeah, it's not unusual that bisect diverts into wrong commit especially with issues that don't reproduce easily or if some unrelated thing is causing also failure at certain step leading to a wrong good/bad guess. Can you test does reverting my guessed commit 2702ea7dbec5 ("i2c: designware: wait for disable/enable only if necessary") fix it? For linux-stable it is good info to know exactly the commit causing regression and mark that in your changelog. It allows linux-stable folks to apply fix to earlier kernels and know versions this fix will still apply if cannot apply where regression was introduced. Fox example: Fixes: commit 2702ea7dbec5 ("i2c: designware: wait for disable/enable only if necessary") Cc: linux-stable # 4.13+ -- Jarkko