Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754131AbcKILU6 (ORCPT ); Wed, 9 Nov 2016 06:20:58 -0500 Received: from foss.arm.com ([217.140.101.70]:50954 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933845AbcKILUk (ORCPT ); Wed, 9 Nov 2016 06:20:40 -0500 Date: Wed, 9 Nov 2016 11:20:00 +0000 From: Mark Rutland To: Benjamin Herrenschmidt Cc: "zhichang.yuan" , catalin.marinas@arm.com, will.deacon@arm.com, robh+dt@kernel.org, bhelgaas@google.com, olof@lixom.net, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, lorenzo.pieralisi@arm.com, linux-kernel@vger.kernel.org, linuxarm@huawei.com, devicetree@vger.kernel.org, linux-pci@vger.kernel.org, linux-serial@vger.kernel.org, minyard@acm.org, liviu.dudau@arm.com, zourongrong@gmail.com, john.garry@huawei.com, gabriele.paoloni@huawei.com, zhichang.yuan02@gmail.com, kantyzc@163.com, xuwei5@hisilicon.com, marc.zyngier@arm.com Subject: Re: [PATCH V5 2/3] ARM64 LPC: Add missing range exception for special ISA Message-ID: <20161109111959.GB17020@leverpostej> References: <1478576829-112707-1-git-send-email-yuanzhichang@hisilicon.com> <1478576829-112707-3-git-send-email-yuanzhichang@hisilicon.com> <20161108114953.GB15297@leverpostej> <1478646779.7430.66.camel@kernel.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1478646779.7430.66.camel@kernel.crashing.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1056 Lines: 24 On Wed, Nov 09, 2016 at 10:12:59AM +1100, Benjamin Herrenschmidt wrote: > On Tue, 2016-11-08 at 11:49 +0000, Mark Rutland wrote: > > I believe that we could theoretically have multiple independent LPC/ISA > > busses, as is possible with PCI on !x86 systems. If the current ISA code > > assumes a singleton bus, I think that's something that needs to be fixed > > up more generically. > > > > I don't see why we should need any architecture-specific code here. Why > > can we not fix up the ISA bus code in drivers/of/address.c such that it > > handles multiple ISA bus instances, and translates all sub-device > > addresses relative to the specific bus instance? > > What in that code prevents that today ? It appears I was mistaken w.r.t. the singleton comment. We can already translate MMIO->MMIO addresses per-instance (in the presence of a ranges property). The big change would be to handle !MMIO translations, for which we'd need a runtime registry of ISA bus instance to find the relevant accessor ops and instance-specific data. Thanks, Mark.