From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-wm0-f41.google.com ([74.125.82.41]:34973 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751044AbcILTjC (ORCPT ); Mon, 12 Sep 2016 15:39:02 -0400 MIME-Version: 1.0 In-Reply-To: <20160912185709.GL18340@uda0271908> References: <20160830183039.GA20056@uda0271908> <20160912032826.GB18340@uda0271908> <20160912185709.GL18340@uda0271908> From: "Matwey V. Kornilov" Date: Mon, 12 Sep 2016 22:38:40 +0300 Message-ID: Subject: Re: musb: isoc pkt loss with pwc To: Bin Liu , "Matwey V. Kornilov" , Alan Stern , hdegoede@redhat.com, linux-media@vger.kernel.org, linux-usb@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-media-owner@vger.kernel.org List-ID: 2016-09-12 21:57 GMT+03:00 Bin Liu : > Hi, > > On Mon, Sep 12, 2016 at 11:52:46AM +0300, Matwey V. Kornilov wrote: >> 2016-09-12 6:28 GMT+03:00 Bin Liu : >> > Hi, >> > >> > On Tue, Aug 30, 2016 at 11:44:33PM +0300, Matwey V. Kornilov wrote: >> >> 2016-08-30 21:30 GMT+03:00 Bin Liu : >> >> > Hi, >> >> > >> >> > On Sun, Aug 28, 2016 at 01:13:55PM +0300, Matwey V. Kornilov wrote: >> >> >> Hello Bin, >> >> >> >> >> >> I would like to start new thread on my issue. Let me recall where the issue is: >> >> >> There is 100% frame lost in pwc webcam driver due to lots of >> >> >> zero-length packages coming from musb driver. >> >> > >> >> > What is the video resolution and fps? >> >> >> >> 640x480 YUV420 10 frames per second. >> >> pwc uses proprietary compression during device-host transmission, but >> >> I don't know how effective it is. >> > >> > The data rate for VGA YUV420 @10fps is 640x480*1.5*10 = 4.6MB/s, which >> > is much higher than full-speed 12Mbps. So the video data on the bus is >> > compressed, not YUV420, I believe. >> > >> >> >> >> > >> >> >> The issue is present in all kernels (including 4.8) starting from the commit: >> >> >> >> >> >> f551e13529833e052f75ec628a8af7b034af20f9 ("Revert "usb: musb: >> >> >> musb_host: Enable HCD_BH flag to handle urb return in bottom half"") >> >> > >> >> > What is the behavior without this commit? >> >> >> >> Without this commit all frames are being received correctly. Single >> > >> > Which means without this commit your camera has been working without >> > issues, and this is a regression with this commit, right? >> > >> >> Right > > Okay, thanks for confirming. > > But we cannot just simply add this flag, as it breaks many other use > cases. I will continue work on this to find a solution which works on > all use cases. > Ok, thank you. > Regards, > -Bin. > -- With best regards, Matwey V. Kornilov. Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia 119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382