Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753345AbdFVUJF (ORCPT ); Thu, 22 Jun 2017 16:09:05 -0400 Received: from www.llwyncelyn.cymru ([82.70.14.225]:57996 "EHLO fuzix.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751224AbdFVUJC (ORCPT ); Thu, 22 Jun 2017 16:09:02 -0400 Date: Thu, 22 Jun 2017 21:08:28 +0100 From: Alan Cox To: Logan Gunthorpe Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-ntb@googlegroups.com, linux-alpha@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-crypto@vger.kernel.org, dri-devel@lists.freedesktop.org, Arnd Bergmann , Greg Kroah-Hartman , Stephen Bates , Richard Henderson , Ivan Kokshaysky , Matt Turner Subject: Re: [PATCH 4/7] alpha: provide ioread64 and iowrite64 implementations Message-ID: <20170622210828.27304f6a@alans-desktop> In-Reply-To: <20170622164817.25515-5-logang@deltatee.com> References: <20170622164817.25515-1-logang@deltatee.com> <20170622164817.25515-5-logang@deltatee.com> Organization: Intel Corporation X-Mailer: Claws Mail 3.14.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 645 Lines: 17 On Thu, 22 Jun 2017 10:48:14 -0600 Logan Gunthorpe wrote: > Alpha implements its own io operation and doesn't use the > common library. Thus to make ioread64 and iowrite64 globally > available we need to add implementations for alpha. > > For this, we simply use calls that chain two 32-bit operations. > (mostly because I don't really understand the alpha architecture.) But this does not do the same thing as an ioread64 with regards to atomicity or side effects on the device. The same is true of the other hacks. You either have a real 64bit single read/write from MMIO space or you don't. You can't fake it. Alan