From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752532AbXLAFQn (ORCPT ); Sat, 1 Dec 2007 00:16:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750776AbXLAFQa (ORCPT ); Sat, 1 Dec 2007 00:16:30 -0500 Received: from gate.crashing.org ([63.228.1.57]:54928 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750723AbXLAFQ3 (ORCPT ); Sat, 1 Dec 2007 00:16:29 -0500 Subject: Re: use of fixmap on non-x86/sh? From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Paul Mundt Cc: Kumar Gala , davem@davemloft.net, wli@holomorphy.com, mingo@redhat.com, ralf@linux-mips.org, linux-kernel@vger.kernel.org In-Reply-To: <20071201010350.GA15027@linux-sh.org> References: <20071201010350.GA15027@linux-sh.org> Content-Type: text/plain Date: Sat, 01 Dec 2007 16:15:37 +1100 Message-Id: <1196486137.13230.128.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.12.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2007-12-01 at 10:03 +0900, Paul Mundt wrote: > There are of course things that make this more attractive on x86, > especially with regards to the global bit and preservation across a > TLB > flush, there's a note in arch/sh/mm/init.c above __set_fixmap() about > that. fixmap doesn't really have any special behaviour that makes an > architecture implementation problematic at least. On ppc, we are mostly looking into memory mapped config space, which for some new PCIe bridges is huge (about 512M per port on the 440SPe). Those processors have 36 bits physical addresses and 32 bits virtual. So I suppose we can just move our current kmap_atomic implementation out of highmem, call it fixmap, and add a slot for use by PCI config space access (those are fully spinlocked, so the per-cpu aspect is just what we need, just like kmap_atomic). Ben.