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

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Message-ID: <20100611095839.GC10894@pengutronix.de>
Date:	Fri, 11 Jun 2010 11:58:39 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Lothar Waßmann <LW@...O-electronics.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

On Fri, Jun 11, 2010 at 11:23:56AM +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.
 
> > Do we do this at the moment? I know at least one implementation of clk_enable 
> > uses a mutex for locking.
> > 
> You are probably talking about the Freescale i.MX51 kernel, that won't
> even boot, if you enable CONFIG_DEBUG_KERNEL, CONFIG_DEBUG_SPINLOCK,
> CONFIG_DEBUG_LOCKDEP and CONFIG_DEBUG_SPINLOCK_SLEEP.
> The mutex in the clock implementation is one of the reasons.
I will have a look into this later today.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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