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

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Message-ID: <20100613222512.GE31045@fluff.org.uk>
Date:	Sun, 13 Jun 2010 23:25:12 +0100
From:	Ben Dooks <ben-linux@...ff.org>
To:	Lothar Wa?mann <LW@...O-electronics.de>
Cc:	Jeremy Kerr <jeremy.kerr@...onical.com>,
	Ben Dooks <ben-linux@...ff.org>,
	Ben Herrenchmidt <benh@...nel.crashing.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC,PATCH 1/2] Add a common struct clk

On Fri, Jun 11, 2010 at 10:14:35AM +0200, Lothar Wa?mann wrote:
> Hi,
> 
> > > > +static inline int clk_enable(struct clk *clk)
> > > > +{
> > > > +	int ret = 0;
> > > > +
> > > > +	if (!clk->ops->enable)
> > > > +		return 0;
> > > > +
> > > > +	mutex_lock(&clk->mutex);
> > > > +	if (!clk->enable_count)
> > > > +		ret = clk->ops->enable(clk);
> > > > +
> > > > +	if (!ret)
> > > > +		clk->enable_count++;
> > > > +	mutex_unlock(&clk->mutex);
> > > > +
> > > > +	return ret;
> > > > +}
> > > 
> Using a mutex in clk_enable()/clk_disable() is a bad idea, since that
> makes it impossible to call those functions in interrupt context.

I think that is a bad idea, unless you can provide otherwise. These
calls can sleep depending on implementation, and thus I would like to
ensure that they are marked as might-sleep.

Is there any specific reason? If so, we need to add some form of ops
where we have _nosleep specificially for this case.

-- 
Ben (ben@...ff.org, http://www.fluff.org/)

  'a smiley only costs 4 bytes'
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