From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f194.google.com ([209.85.192.194]:32789 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754424AbcKDBM0 (ORCPT ); Thu, 3 Nov 2016 21:12:26 -0400 Date: Fri, 4 Nov 2016 09:12:21 +0800 From: Peter Chen To: Felipe Balbi Cc: David Miller , linux-usb@vger.kernel.org, ville.syrjala@linux.intel.com, stable@vger.kernel.org Subject: Re: [PATCH] usb: gadget: u_ether: remove interrupt throttling Message-ID: <20161104011220.GA17925@b29397-desktop> References: <20161101112959.19640-1-felipe.balbi@linux.intel.com> <20161102060202.GD28525@b29397-desktop> <20161102.112254.1243059410485662386.davem@davemloft.net> <20161103002300.GA894@b29397-desktop> <87wpglqc15.fsf@linux.intel.com> <20161103090310.GC894@b29397-desktop> <87lgx0n8u4.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87lgx0n8u4.fsf@linux.intel.com> Sender: stable-owner@vger.kernel.org List-ID: On Thu, Nov 03, 2016 at 12:42:11PM +0200, Felipe Balbi wrote: > > Hi, > > Peter Chen writes: > >> Peter Chen writes: > >> > On Wed, Nov 02, 2016 at 11:22:54AM -0400, David Miller wrote: > >> >> From: Peter Chen > >> >> Date: Wed, 2 Nov 2016 14:02:02 +0800 > >> >> > >> >> > Felipe, it may increase cpu utilization since more interrupts will be there, > >> >> > it may affect the SoC which has lower cpu frequency. This code existed > >> >> > many years, why this problem has only reported at dwc3 recently? > >> >> > >> >> It's a bug, and it's going to cause TCP sockets to potentially hang. > >> >> > >> > > >> > For some controllers, it is, so we need to add parameter for user > >> > to see if interrupt migration is supported or not. > >> > >> not for some controller, for ALL networking drivers. > >> > >> > But just like some ethernet controllers, some USB controllers support > >> > hardware timeout mechanism which interrupt will be triggered after > >> > some uFrame occurs if the transaction has completed but not required > >> > to interrupt, it is used to support interrupt migration like ethernet. > >> > >> you're missing the point. What Dave Miller is saying is that it's ALWAYS > >> a bug to delay completion of SKBs. The only thing you're doing with > >> chipidea is delaying interrupt by up to 125us; which is still a bug from > >> the point of view of the networking layer, but it's more difficult to > >> perceive any problems because of the short time where interrupt is > >> delayed. > >> > > > > If it is ALWAYS a bug to delay completion of SKBs, how the local > > ethernet driver designs interrupt migration? > > what driver are you talking about? Which "local" ethernet driver? > The ethernet driver located at drivers/net/ethernet, its device uses RJ45 connector to communicate. -- Best Regards, Peter Chen