Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755113Ab0FNGly (ORCPT ); Mon, 14 Jun 2010 02:41:54 -0400 Received: from metis.ext.pengutronix.de ([92.198.50.35]:37180 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754752Ab0FNGlx (ORCPT ); Mon, 14 Jun 2010 02:41:53 -0400 Date: Mon, 14 Jun 2010 08:40:28 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Lothar =?iso-8859-1?Q?Wa=DFmann?= Cc: Benjamin Herrenschmidt , Jeremy Kerr , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Ben Dooks Subject: Re: [RFC,PATCH 1/2] Add a common struct clk Message-ID: <20100614064028.GA12159@pengutronix.de> References: <1275636608.606606.450179637764.0.gpush@pororo> <201006111557.12249.jeremy.kerr@canonical.com> <19473.61547.684572.647641@ipc1.ka-ro> <201006111718.47426.jeremy.kerr@canonical.com> <19474.172.742782.972629@ipc1.ka-ro> <20100611095839.GC10894@pengutronix.de> <19474.2817.333749.485028@ipc1.ka-ro> <1276319643.1962.181.camel@pasglop> <19477.52889.982995.407051@ipc1.ka-ro> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <19477.52889.982995.407051@ipc1.ka-ro> User-Agent: Mutt/1.5.18 (2008-05-17) 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: 1569 Lines: 40 Hello Lothar, On Mon, Jun 14, 2010 at 08:39:21AM +0200, Lothar Wa?mann wrote: > Hi, > > Benjamin Herrenschmidt writes: > > On Fri, 2010-06-11 at 12:08 +0200, Lothar Wa?mann wrote: > > > Hi, > > > > > > > > > > Using a mutex in clk_enable()/clk_disable() is a bad idea, since that > > > > > > > makes it impossible to call those functions in interrupt context. > > > > IMHO if a device generates an irq its clock should already be on. This > > > > way you don't need to enable or disable a clock in irq context. > > > > > > > You may want to disable a clock in the IRQ handler. The VPU driver in > > > the Freescale BSP for i.MX51 does exactly this. > > > Anyway I don't see any reason for using a mutex here instead of > > > spin_lock_irq_save() as all other implementations do. > > > > Because you suddenly make it impossible to sleep inside enable/disable > ^^^^^^^^^^^^^^^^^^^^^^^^^^^ > ??? > All implementations so far use spin_lock_irq_save()! > > How would you be able to sleep with a mutex held? > If you hold a lock you must not sleep, no matter what sort of lock it > is. That's wrong. With a mutex hold you may sleep. 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/