Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261349AbVCaLRd (ORCPT ); Thu, 31 Mar 2005 06:17:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261329AbVCaLRN (ORCPT ); Thu, 31 Mar 2005 06:17:13 -0500 Received: from general.keba.co.at ([193.154.24.243]:10681 "EHLO helga.keba.co.at") by vger.kernel.org with ESMTP id S261340AbVCaLPh convert rfc822-to-8bit (ORCPT ); Thu, 31 Mar 2005 06:15:37 -0500 X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 8BIT Subject: RE: 2.6.11, USB: High latency? Date: Thu, 31 Mar 2005 13:15:23 +0200 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: 2.6.11, USB: High latency? Thread-Index: AcU1QOmYmgzgBJegTNu7pzr78CzZrAAoM+1Q From: "kus Kusche Klaus" To: "Alan Stern" Cc: , Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1442 Lines: 44 > The latencies are almost certainly caused by the USB host controller > driver. I'm planning improvements to uhci-hcd which should > help reduce > the latency, but it will still be on the large side. And I > won't have > time to write the changes to the driver for several months. Any numbers about the expected "large side"? We would need <30 microseconds irq latency, and <<1 milliseconds rt application latency. > The best solution is to stop using uhci-hcd. Get a PCI card > with an OHCI > or EHCI (high-speed) controller. They do much more work in hardware, > reducing the amount of time the driver needs to spend with interrupts > disabled. The hardware is invariable. It is an embedded system with no PCI slots. And it seems to be possible with UHCI, because vxWorks allows USB stick transfers in operation without missing latency requirements. I do not require rt on the USB, it may block its own irq as long as it likes, but it should not affect other irqs. -- Klaus Kusche Entwicklung Software - Steuerung Software Development - Control KEBA AG A-4041 Linz Gewerbepark Urfahr Tel +43 / 732 / 7090-3120 Fax +43 / 732 / 7090-8919 E-Mail: kus@keba.com www.keba.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/