From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from moutng.kundenserver.de ([212.227.126.171]:55679 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754283Ab3A3Jru (ORCPT ); Wed, 30 Jan 2013 04:47:50 -0500 From: Arnd Bergmann To: Jason Gunthorpe Subject: Re: [PATCH v2 05/27] arm: pci: add a align_resource hook Date: Wed, 30 Jan 2013 09:46:53 +0000 Cc: Thomas Petazzoni , "Russell King - ARM Linux" , Bjorn Helgaas , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Lior Amsalem , Andrew Lunn , Jason Cooper , Stephen Warren , Thierry Reding , "Eran Ben-Avi" , Nadav Haklai , Maen Suleiman , Shadi Ammouri , Gregory Clement , Tawfik Bayouk References: <1359399397-29729-1-git-send-email-thomas.petazzoni@free-electrons.com> <201301291645.08040.arnd@arndb.de> <20130130045655.GE5734@obsidianresearch.com> In-Reply-To: <20130130045655.GE5734@obsidianresearch.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Message-Id: <201301300946.54040.arnd@arndb.de> Sender: linux-pci-owner@vger.kernel.org List-ID: On Wednesday 30 January 2013, Jason Gunthorpe wrote: > > But we normally only assign a 64 KB I/O window to each PCI host bridge. > > Requiring PCI bridges to be space 64 KB apart would mean that we cannot > > actually support bridges at all. > > The PCI resource code uses full 32 bit integers when it handles IO > addresses, so this actually does sort of work out. However, we only reserve 1 MB (I think) virtual address window for all I/O spaces of all PCI domains combined, at a fixed location (0xfee00000). This means we can have at most 16 such windows at run-time. That can be changed if necessary, but it seems like overkill when in practice you only need a few bytes at most. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Wed, 30 Jan 2013 09:46:53 +0000 Subject: [PATCH v2 05/27] arm: pci: add a align_resource hook In-Reply-To: <20130130045655.GE5734@obsidianresearch.com> References: <1359399397-29729-1-git-send-email-thomas.petazzoni@free-electrons.com> <201301291645.08040.arnd@arndb.de> <20130130045655.GE5734@obsidianresearch.com> Message-ID: <201301300946.54040.arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wednesday 30 January 2013, Jason Gunthorpe wrote: > > But we normally only assign a 64 KB I/O window to each PCI host bridge. > > Requiring PCI bridges to be space 64 KB apart would mean that we cannot > > actually support bridges at all. > > The PCI resource code uses full 32 bit integers when it handles IO > addresses, so this actually does sort of work out. However, we only reserve 1 MB (I think) virtual address window for all I/O spaces of all PCI domains combined, at a fixed location (0xfee00000). This means we can have at most 16 such windows at run-time. That can be changed if necessary, but it seems like overkill when in practice you only need a few bytes at most. Arnd