From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Date: Tue, 01 Feb 2011 14:00:24 +0000 Subject: Re: Locking in the clk API, part 2: clk_prepare/clk_unprepare Message-Id: <20110201140024.GZ1147@pengutronix.de> List-Id: References: <201102011711.31258.jeremy.kerr@canonical.com> <20110201105449.GY1147@pengutronix.de> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: linux-arm-kernel@lists.infradead.org On Tue, Feb 01, 2011 at 10:05:56PM +0900, Jassi Brar wrote: > 2011/2/1 Uwe Kleine-K=F6nig : >=20 > ..... >=20 > > Do you plan to handle the case that clk_enable is called while prepare > > isn't completed (considering the special case "not called at all")? > > Maybe BUG_ON(clk->ops->prepare && !clk->prepare_count)? > Sounds better than the second option. >=20 > > Alternatively don't force the sleep in clk_prepare (e.g. by protecting > > prepare_count by a spinlock (probably enable_lock)) and call clk_prepare > > before calling clk->ops->enable? > That might result in a driver working on some platforms(those have > atomic clk_prepare) > and not on others(those have sleeping). The first option has the same result. E.g. on some platforms clk->ops->prepare might be NULL, on others it's not. Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | http://www.pengutronix.de/ | From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756944Ab1BAOBE (ORCPT ); Tue, 1 Feb 2011 09:01:04 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:34086 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756699Ab1BAOBC (ORCPT ); Tue, 1 Feb 2011 09:01:02 -0500 Date: Tue, 1 Feb 2011 15:00:24 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Jassi Brar Cc: Jeremy Kerr , Nicolas Pitre , Lorenzo Pieralisi , Russell King , linux-sh@vger.kernel.org, Ben Herrenschmidt , Sascha Hauer , Paul Mundt , linux-kernel@vger.kernel.org, Dima Zavin , Saravana Kannan , Ben Dooks , Vincent Guittot , linux-arm-kernel@lists.infradead.org Subject: Re: Locking in the clk API, part 2: clk_prepare/clk_unprepare Message-ID: <20110201140024.GZ1147@pengutronix.de> References: <201102011711.31258.jeremy.kerr@canonical.com> <20110201105449.GY1147@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) X-SA-Exim-Connect-IP: 2001:6f8:1178:2:215:17ff:fe12:23b0 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 01, 2011 at 10:05:56PM +0900, Jassi Brar wrote: > 2011/2/1 Uwe Kleine-König : > > ..... > > > Do you plan to handle the case that clk_enable is called while prepare > > isn't completed (considering the special case "not called at all")? > > Maybe BUG_ON(clk->ops->prepare && !clk->prepare_count)? > Sounds better than the second option. > > > Alternatively don't force the sleep in clk_prepare (e.g. by protecting > > prepare_count by a spinlock (probably enable_lock)) and call clk_prepare > > before calling clk->ops->enable? > That might result in a driver working on some platforms(those have > atomic clk_prepare) > and not on others(those have sleeping). The first option has the same result. E.g. on some platforms clk->ops->prepare might be NULL, on others it's not. Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Tue, 1 Feb 2011 15:00:24 +0100 Subject: Locking in the clk API, part 2: clk_prepare/clk_unprepare In-Reply-To: References: <201102011711.31258.jeremy.kerr@canonical.com> <20110201105449.GY1147@pengutronix.de> Message-ID: <20110201140024.GZ1147@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Feb 01, 2011 at 10:05:56PM +0900, Jassi Brar wrote: > 2011/2/1 Uwe Kleine-K?nig : > > ..... > > > Do you plan to handle the case that clk_enable is called while prepare > > isn't completed (considering the special case "not called at all")? > > Maybe BUG_ON(clk->ops->prepare && !clk->prepare_count)? > Sounds better than the second option. > > > Alternatively don't force the sleep in clk_prepare (e.g. by protecting > > prepare_count by a spinlock (probably enable_lock)) and call clk_prepare > > before calling clk->ops->enable? > That might result in a driver working on some platforms(those have > atomic clk_prepare) > and not on others(those have sleeping). The first option has the same result. E.g. on some platforms clk->ops->prepare might be NULL, on others it's not. Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |