Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753785Ab1BAPyF (ORCPT ); Tue, 1 Feb 2011 10:54:05 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:45364 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752949Ab1BAPyC (ORCPT ); Tue, 1 Feb 2011 10:54:02 -0500 Date: Tue, 1 Feb 2011 16:53:44 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Russell King - ARM Linux Cc: Jeremy Kerr , Dima Zavin , Saravana Kannan , Lorenzo Pieralisi , linux-sh@vger.kernel.org, Ben Herrenschmidt , Sascha Hauer , linux-kernel@vger.kernel.org, Paul Mundt , Ben Dooks , Vincent Guittot , linux-arm-kernel@lists.infradead.org, Nicolas Pitre Subject: Re: Locking in the clk API, part 2: clk_prepare/clk_unprepare Message-ID: <20110201155344.GF1147@pengutronix.de> References: <201102011711.31258.jeremy.kerr@canonical.com> <20110201105449.GY1147@pengutronix.de> <20110201131512.GH31216@n2100.arm.linux.org.uk> <20110201141837.GA1147@pengutronix.de> <20110201143932.GK31216@n2100.arm.linux.org.uk> <20110201151846.GD1147@pengutronix.de> <20110201152458.GP31216@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20110201152458.GP31216@n2100.arm.linux.org.uk> 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 Content-Length: 1060 Lines: 34 On Tue, Feb 01, 2011 at 03:24:58PM +0000, Russell King - ARM Linux wrote: > On Tue, Feb 01, 2011 at 04:18:46PM +0100, Uwe Kleine-K?nig wrote: > > yeah, didn't thought about multiple consumers, so (as Jeremy suggested) > > the right thing is to sleep until CLK_BUSY is cleared. > > A simpler way to write this is: > > int clk_prepare(struct clk *clk) > { > int ret = 0; > > mutex_lock(&clk->mutex); > if (clk->prepared == 0) > ret = clk->ops->prepare(clk); > if (ret == 0) > clk->prepared++; > mutex_unlock(&clk->mutex); > > return ret; > } But you cannot call this in atomic context when you know the clock is already prepared. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/