Return-path: Received: from s3.sipsolutions.net ([5.9.151.49]:42244 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755575AbbA1USk (ORCPT ); Wed, 28 Jan 2015 15:18:40 -0500 Message-ID: <1422430643.1973.1.camel@sipsolutions.net> (sfid-20150128_230953_458583_5D948B2A) Subject: Re: [PATCH] ath10k: Replace ioread with wmb for data sync From: Johannes Berg To: Peter Oh Cc: Bob Copeland , ath10k@lists.infradead.org, linux-wireless@vger.kernel.org Date: Wed, 28 Jan 2015 08:37:23 +0100 In-Reply-To: <54C875FD.3070101@qca.qualcomm.com> (sfid-20150128_064104_435635_7E681844) References: <1422311118-11320-1-git-send-email-poh@qca.qualcomm.com> <20150127213349.GA24933@localhost> <54C824DC.5080804@qca.qualcomm.com> <20150128043005.GB24933@localhost> <54C875FD.3070101@qca.qualcomm.com> (sfid-20150128_064104_435635_7E681844) Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Tue, 2015-01-27 at 21:39 -0800, Peter Oh wrote: > > Ok, sure, but I/O ordering two different writes, and ensuring device > > has seen a posted write, are related but different things, no? > yes, they are different and wmb guarantees both. No, wmb() doesn't. I'd be very surprised if it had any side effect on the PCI bus even on ARM. Read Documentation/memory-barriers.txt. And to understand (PCI) posted writes, wikipedia helps: http://en.wikipedia.org/wiki/Posted_write johannes