Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753284Ab2BDPjE (ORCPT ); Sat, 4 Feb 2012 10:39:04 -0500 Received: from mail-tul01m020-f174.google.com ([209.85.214.174]:39590 "EHLO mail-tul01m020-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750847Ab2BDPjB convert rfc822-to-8bit (ORCPT ); Sat, 4 Feb 2012 10:39:01 -0500 MIME-Version: 1.0 In-Reply-To: <4F2AA642.1030400@linux.intel.com> References: <20120121082857.GC32134@elte.hu> <20120121165830.GA9216@elte.hu> <20120131115855.5861bad7@pyramind.ukuu.org.uk> <20120131120922.GD32010@elte.hu> <20120131121820.58a1db97@pyramind.ukuu.org.uk> <20120131122339.GG32010@elte.hu> <1328144756.2768.57.camel@dabdike.int.hansenpartnership.com> <4F2AA642.1030400@linux.intel.com> Date: Sun, 5 Feb 2012 00:39:00 +0900 Message-ID: Subject: Re: [PATCH] NVMe: Fix compilation on architecturs without readq/writeq From: Hitoshi Mitake To: "H. Peter Anvin" Cc: James Bottomley , Linus Torvalds , Ingo Molnar , Alan Cox , Matthew Wilcox , Roland Dreier , Andrew Morton , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1675 Lines: 41 On Fri, Feb 3, 2012 at 00:05, H. Peter Anvin wrote: > On 02/01/2012 05:05 PM, James Bottomley wrote: >> >> >> Incidentally, the last time this came up was with mpt fusion: for a >> write to a 64 bit register, it didn't care about order, but it did care >> about interleaving as in if you write one half of a 64 bit register and >> then write to another register, the 64 bit register effectively gets >> written with zeros in the part you didn't write to, so we had to put a >> spin lock in the open coded writeb/w/l/q() to make sure the card didn't >> get interleaved writes. >> > > There are always going to be hardware which have specific needs, and for > those open-coding makes sense, but the littleendian/bigendian pair is going > to cover ~90% of users and make sense to can. > > I worked myself on a driver (which sadly never shipped) which had an WC > window and a UC window... the final write in a series had a completion bit > in it and would go to the UC window after setting up a whole chunk of > operations in the WC window (writing UC memory flushes WC memory ahead of > it.) > > Thus, the two-part breakdown of writeq() to the UC window had to write the > low half to the WC window instead. ?This is clearly not generic. > > ? ? ? ?-hpa > > Because of my ignorant, I don't know the words "UC window" and "WC window" in this context. Could you teach me? -- Hitoshi Mitake h.mitake@gmail.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/