From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin LaHaise Subject: Re: [PATCH 2/3] x86_64: Define 128-bit memory-mapped I/O operations Date: Wed, 22 Aug 2012 10:30:54 -0400 Message-ID: <20120822143054.GD9803@kvack.org> References: <1345598601.2659.76.camel@bwh-desktop.uk.solarflarecom.com> <503437D4.8090706@zytor.com> <1345601051.2659.93.camel@bwh-desktop.uk.solarflarecom.com> <20120821.193446.1534561579811962053.davem@davemloft.net> <503450E2.2040504@zytor.com> <1345642009.15245.0.camel@deadeye.wl.decadent.org.uk> <1345645499.15245.8.camel@deadeye.wl.decadent.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Linus Torvalds , "H. Peter Anvin" , David Miller , tglx@linutronix.de, mingo@redhat.com, netdev@vger.kernel.org, linux-net-drivers@solarflare.com, x86@kernel.org To: Ben Hutchings Return-path: Received: from kanga.kvack.org ([205.233.56.17]:55576 "EHLO kanga.kvack.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753654Ab2HVOzZ (ORCPT ); Wed, 22 Aug 2012 10:55:25 -0400 Content-Disposition: inline In-Reply-To: <1345645499.15245.8.camel@deadeye.wl.decadent.org.uk> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Aug 22, 2012 at 03:24:59PM +0100, Ben Hutchings wrote: > -#ifdef EFX_USE_QWORD_IO > +#if defined(EFX_USE_OWORD_IO) > + _efx_writeo(efx, value->u128, reg); > +#elif defined(EFX_USE_QWORD_IO) > _efx_writeq(efx, value->u64[0], reg + 0); > _efx_writeq(efx, value->u64[1], reg + 8); > #else This looks like a perfect fit for write combining. I have traces showing that enabling write combining on MMIO does indeed generate a single PCIe transaction on at least a couple of different current systems. Why is that not an option? -ben -- "Thought is the essence of where you are now."