From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael Chan" Subject: Re: [PATCH 10/11][TG3]: Reduce spurious interrupts. Date: Fri, 04 May 2007 18:45:58 -0700 Message-ID: <1178329558.4859.38.camel@dell> References: <1178326521.4859.26.camel@dell> <463BD303.7000500@garzik.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: "David Miller" , "netdev" To: "Jeff Garzik" Return-path: Received: from mms2.broadcom.com ([216.31.210.18]:2328 "EHLO mms2.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031014AbXEEA6n (ORCPT ); Fri, 4 May 2007 20:58:43 -0400 In-Reply-To: <463BD303.7000500@garzik.org> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, 2007-05-04 at 20:42 -0400, Jeff Garzik wrote: > Michael Chan wrote: > > [TG3]: Reduce spurious interrupts. > > > > Spurious interrupts are often encountered especially on systems > > using the 8259 PIC mode. This is because the I/O write to deassert > > the interrupt is posted and won't get to the chip immediately. As > > a result, the IRQ may remain asserted after the IRQ handler exits, > > causing spurious interrupts. > > > > An unconditional read to flush the I/O write to force the IRQ to de- > > assert immediately is not desirable because it impacts performance in > > the fast path. So we only do this after we have some indications of > > spurious interrupts. > > > > Signed-off-by: Michael Chan > > hmmmm, this is a bit questionable that it needs to be here. > > I think it's just a fact of life that it is important to flush certain > writes... > > I'm not sure a driver needs to be adding code to avoid the obvious > solution. It would be annoying if all drivers had code to do this. We had a discussion about 2 years ago and David decided to remove the I/O read to improve performance. Since then a small number of users have been complaining about spurious interrupts. We can add back the unconditional read or do this detection thing which I agree is somewhat annoying. David, what do you think?