From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathias Nyman Subject: Re: [PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller Date: Mon, 19 Oct 2015 14:25:49 +0300 Message-ID: <5624D33D.5090807@intel.com> References: <1443495698-32233-1-git-send-email-chunfeng.yun@mediatek.com> <1443495698-32233-5-git-send-email-chunfeng.yun@mediatek.com> <561FBC40.7020100@linux.intel.com> <1445131519.17024.10.camel@mhfsdcap03> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1445131519.17024.10.camel@mhfsdcap03> Sender: linux-kernel-owner@vger.kernel.org To: chunfeng yun , Mathias Nyman Cc: Rob Herring , Mark Rutland , Matthias Brugger , Felipe Balbi , Sascha Hauer , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Roger Quadros , linux-usb@vger.kernel.org, linux-mediatek@lists.infradead.org, John Crispin , Daniel Kurtz , Sergei Shtylyov , Kishon Vijay Abraham I , Pawel Moll , Ian Campbell , Kumar Gala , Greg Kroah-Hartman List-Id: devicetree@vger.kernel.org >> >> So basically we are trying to use as many microframes as possible with as few packets >> per microframe as possible. >> >> Did I understand this correctly? > Yes, you are right. > >> How will devices react if they expect to get 16 packets every 16th microframe, >> but they get one packet every microframe instead? > I think that the synchronous endpoint must specify its period by > bInterval, but can't specify how data should be transfered during the > period by the host, and it just only receives data passively. So the > device can receive data correctly in the case(bInterval is 5). > > quote from usb3_r1.0 section4.4.8 Isochronous Transfers: > "The host can request data from the device or send data to the device at > any time during the service interval for a particular endpoint on that > device" > As I understand the 4.4.8 section it just means the device can't assume a fixed time interval between transfers, meaning that the host can use the last microframe in one esit and the first microframe in the next esit, but still only use 1 microframe per esit. Section 8.12.6.1 describes how a 11 packet isoc transfer is allowed to be split to 1 burst of 11 packets, 2 burst (8 + 3), 3 burst (4+4+3) 6 bursts (2+2+2+2+2+1) or 11 bursts of 1. These are however all within the same microframe. Splitting the transfer into several microframes in a esit kind of makes the whole interval concept pointless. -Mathias