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Date: Mon, 14 Jun 2010 08:40:28 +0200 From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de> To: Lothar Waßmann <LW@...O-electronics.de> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>, Jeremy Kerr <jeremy.kerr@...onical.com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Ben Dooks <ben-linux@...ff.org> Subject: Re: [RFC,PATCH 1/2] Add a common struct clk Hello Lothar, On Mon, Jun 14, 2010 at 08:39:21AM +0200, Lothar Waßmann wrote: > Hi, > > Benjamin Herrenschmidt writes: > > On Fri, 2010-06-11 at 12:08 +0200, Lothar Waßmann 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-König | 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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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