linux-kernel - Re: [RFC,PATCH 1/2] Add a common struct clk

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Date:	Fri, 11 Jun 2010 12:08:01 +0200
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Jeremy Kerr <jeremy.kerr@...onical.com>,
	linux-arm-kernel@...ts.infradead.org,
	Ben Herrenchmidt <benh@...nel.crashing.org>,
	linux-kernel@...r.kernel.org, Ben Dooks <ben-linux@...ff.org>
Subject: Re: [RFC,PATCH 1/2] Add a common struct clk

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.


Lothar Waßmann
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