From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1JC3IA-0005tU-Sd for qemu-devel@nongnu.org; Mon, 07 Jan 2008 20:30:10 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1JC3I9-0005rA-4K for qemu-devel@nongnu.org; Mon, 07 Jan 2008 20:30:10 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1JC3I8-0005qp-Te for qemu-devel@nongnu.org; Mon, 07 Jan 2008 20:30:08 -0500 Received: from mail.codesourcery.com ([65.74.133.4]) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1JC3I8-0003rr-En for qemu-devel@nongnu.org; Mon, 07 Jan 2008 20:30:08 -0500 From: Paul Brook Subject: Re: [Qemu-devel] [PATCH] USB 2.0 EHCI emulation Date: Tue, 8 Jan 2008 01:30:02 +0000 References: <64F9B87B6B770947A9F8391472E0321610478FD1@ehost011-8.exch011.intermedia.net> In-Reply-To: <64F9B87B6B770947A9F8391472E0321610478FD1@ehost011-8.exch011.intermedia.net> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200801080130.04161.paul@codesourcery.com> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: KVM , Roni Luxenberg , Arnon Gilboa > -The host kernel was configured with dynamic tick & hi-res timers, to > allow the desired timer resolution. USB 2.0 microframe is 125usec. Requiring a 8kHz timer is a non-starter. The 100kHz "retry" timer is even more bogus. Qemu isn't capable of this kind of realtime response. You need to figure out an implementation that doesn't require extremely fine grained timers. In paractice you're unlikely to get better than 10ms timer resolution, and 100ms latency isn't that uncommon. Paul