From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7 Date: Fri, 19 Apr 2013 20:54:25 +0200 Message-ID: <517192E1.1090609@gmail.com> References: <515C013D.8090909@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-bk0-f41.google.com (mail-bk0-f41.google.com [209.85.214.41]) by alsa0.perex.cz (Postfix) with ESMTP id 5FFEF2650ED for ; Fri, 19 Apr 2013 20:54:17 +0200 (CEST) Received: by mail-bk0-f41.google.com with SMTP id i18so1858316bkv.28 for ; Fri, 19 Apr 2013 11:54:17 -0700 (PDT) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Takashi Iwai Cc: "alsa-devel@alsa-project.org" , 1136110@bugs.launchpad.net, Alan Stern , Joseph Salisbury , Tyson Tan , David Henningsson List-Id: alsa-devel@alsa-project.org On 03.04.2013 12:25, Takashi Iwai wrote: > At Wed, 03 Apr 2013 12:15:25 +0200, > David Henningsson wrote: >> >> Hi ALSA developers, >> >> Just to get your attention here on what seems to be an USB audio >> regression. >> >> The bug is described in detail here: >> >> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all >> >> Quoting the bug: >> >> " >> This bug seems to affect only a certain kind of hardware, which is >> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such >> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so >> called "Synchronous USB DAC", uses the clock hosted by the mother board, >> which is not affected by this bug. >> >> When this bug affects an asynchronous USB DAC, the audio played by the >> DAC is constantly interrupted. The playback itself does not stop, but >> the output becomes discontinous, filling with constant crackling noises, >> destroying everything the DAC plays. >> " >> >> According to the bug reporter, which seems to have done quite a bit of >> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable >> kernels and the bug also lists a few commits which could be the cause, >> none under sound/usb though. > > Yes, there is no commits regarding usb-audio itself between 3.8-rc6 > and rc7, so the likely culprit is in drivers/usb (usually either > drivers/usb/host or drivers/usb/core). There are a bunch of changes > there, so further bisection would be appreciated. Ok, Joseph Salisbury has build some bisection kernels, and Tyson Tan relentlessly tested all of them, and it turns out that 3e619d0415 ("USB: EHCI: fix bug in scheduling periodic split transfers") Is the first bad commit. Also, reverting this commit from the current mainline head makes the problem disappear. Alan, any idea? https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110 Thanks, Daniel