From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932183AbWHKLmF (ORCPT ); Fri, 11 Aug 2006 07:42:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932149AbWHKLmE (ORCPT ); Fri, 11 Aug 2006 07:42:04 -0400 Received: from outpipe-village-512-1.bc.nu ([81.2.110.250]:11225 "EHLO lxorguk.ukuu.org.uk") by vger.kernel.org with ESMTP id S932173AbWHKLmC (ORCPT ); Fri, 11 Aug 2006 07:42:02 -0400 Subject: Re: Serial driver 8250 hangs the kernel with the VIA Nehemiah... From: Alan Cox To: Chris Pringle Cc: linux-kernel@vger.kernel.org In-Reply-To: <44DC6524.4000401@miranda.com> References: <44DC6524.4000401@miranda.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Fri, 11 Aug 2006 13:02:08 +0100 Message-Id: <1155297728.24077.52.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.2 (2.6.2-1.fc5.5) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ar Gwe, 2006-08-11 am 12:08 +0100, ysgrifennodd Chris Pringle: > > Unlikely as it would affect both. More likely would be that the ISA bus > > clock is generated off the PCI bus clock and you have one of the > > multipliers wrong or too high for the board. > > > Thats interesting, but wouldn't this produce strange side affects for > the 2.4 kernel as well? 2.4 works fine on both VIAs and Celerons. That I wonder about. The power management stuff and some other things that matter for timing are different however. > I'll give the interrupt disabling a go... Its just a guess but if you have low latency stuff, you have pre-empt enabled and you actually depend upon the semantics of inb_p/outb_p giving delays reliably then I'm not convinced are guarantees are strong enough Specifically we don't have any pre-empt protection between the I/O delay and the I/O so we could violate it as we don't have pre-empt disables in inb_p/outb_p and if your CPU context switch is quick enough it could trigger a problem. Alan