From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1J1mmd-0007uk-HJ for qemu-devel@nongnu.org; Mon, 10 Dec 2007 12:51:11 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1J1mmc-0007tF-5c for qemu-devel@nongnu.org; Mon, 10 Dec 2007 12:51:11 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1J1mmb-0007t3-Sz for qemu-devel@nongnu.org; Mon, 10 Dec 2007 12:51:09 -0500 Received: from wr-out-0506.google.com ([64.233.184.234]) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1J1mmb-0005f1-G4 for qemu-devel@nongnu.org; Mon, 10 Dec 2007 12:51:09 -0500 Received: by wr-out-0506.google.com with SMTP id c37so5606217wra for ; Mon, 10 Dec 2007 09:51:07 -0800 (PST) Message-ID: Date: Mon, 10 Dec 2007 19:51:05 +0200 From: "Blue Swirl" Subject: Re: [Qemu-devel] high resolution timer question In-Reply-To: <475D3839.8040207@earthlink.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <475D3839.8040207@earthlink.net> 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 On 12/10/07, Robert Reif wrote: > Writing data to a serial port on the sparc emulation happens immediately. > I would like to throttle the write speed to match the actual baud rate. > What's the best way to do this in qemu? Will QEMUTimer work for a > 1 millisecond timer? Do you mean that you want the serial port to match the host speed so that for example, at 9600 baud, target would only receive 9600 bits per second? Or do you mean that the emulated CPU should see bits arriving at the same rate that the real CPU would see compared to CPU execution speed? On the positive side, this would fix a bug with serial interrupts arriving too fast which can trigger Linux panics. But this would also complicate the design because currently the devices do not need to emulate any internal buffers. I think the throttling should be done at CharDriver level so that all targets and also other devices, like parallel ports (SUNW,bpp anyone?) can benefit. It should be turned off when talking to real hardware on the host.