From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758294Ab2CALag (ORCPT ); Thu, 1 Mar 2012 06:30:36 -0500 Received: from opensource.wolfsonmicro.com ([80.75.67.52]:39830 "EHLO opensource.wolfsonmicro.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754202Ab2CALae (ORCPT ); Thu, 1 Mar 2012 06:30:34 -0500 Date: Thu, 1 Mar 2012 11:30:32 +0000 From: Mark Brown To: "Ying-Chun Liu (PaulLiu)" Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linaro-dev@lists.linaro.org, patches@linaro.org, Samuel Ortiz , Shawn Guo Subject: Re: [PATCH v5 1/2] mfd: Add anatop mfd driver Message-ID: <20120301113031.GD3124@opensource.wolfsonmicro.com> References: <1330593052-15184-1-git-send-email-paul.liu@linaro.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="OaZoDhBhXzo6bW1J" Content-Disposition: inline In-Reply-To: <1330593052-15184-1-git-send-email-paul.liu@linaro.org> X-Cookie: You may be recognized soon. Hide. 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 --OaZoDhBhXzo6bW1J Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Mar 01, 2012 at 05:10:51PM +0800, Ying-Chun Liu (PaulLiu) wrote: > + spin_lock(&adata->reglock); > + val = readl(adata->ioreg + addr); > + spin_unlock(&adata->reglock); Do you really need to take a lock for a single read operation from a memory mapped register? I'd expect this to be atomic in itself. You need to lock on read/modify/write cycles to make sure that you don't get a read/read/modify/modify/write/write and misplace one of the modifies but that's not an issue for an isolated read. --OaZoDhBhXzo6bW1J Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAEBAgAGBQJPT1voAAoJEBus8iNuMP3dWSkP/i2qSXLpNISFEJqiBxtEhiTg AMOdDZo10K9LnAuAoeVjORqNqe2nL+U4vSNCytieK5LNbO8e69abIuwI1pDgR3vw d9HTDnCwBlEXhwmbpdS94PGJPs9bRK9HXLBwH06jkrndq1qarcJ4WkXF6ttfYema fA1ZvthzP7zB4xsZJPIR3Du2S/dZH9L7rJXSab4GJfUsx8b9n6hb+JLaeZRI/b38 vqirUFwrY9BY84dKTKi09T7mUgpkqNJbexTtPEx93oefQRlAZJA1ccy2X6qnwcAN D3qQLZJMf3miGuOpt1fYxRrPZ+iOY/GbhTppFhEn6hbg7QMxogkcihb93zB6vB6S LVH7vLllNk2GQXD+yHW6P1MAfzOQZqT0w0YKisNF05G9/O1ZnWydv41ylYNwl85F iveiZlrtOiqljeE/s9d/9pR4pKewl88BNrt+jU9NQ1OC7sRmTKhuCXQe/blcLLDQ Me9tGHzJ9X7k9as5cDSr6ezvVYuALKheM4R29j2hkkScjV0b2x+W8n0XUbZXLQYg fU5jJMCpA6NiaDgTIbVRrJ3qY++aFJARBItpcKjXp8HxAkfhhVgPuqbwtXcpZPRU r5EmEcXbK3AWoycIcC29gnRZi0802KZ8FpF364ihAInuX9uBoPD94CZuktJSH5Q5 Wb6JK/mBOXrp/zsQXqFB =30p8 -----END PGP SIGNATURE----- --OaZoDhBhXzo6bW1J--