linux-kernel - Re: [PATCH 1/4] clk: Add a generic clock infrastructure

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Date:	Fri, 20 May 2011 15:25:24 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Sascha Hauer <s.hauer@...gutronix.de>
cc:	Jeremy Kerr <jeremy.kerr@...onical.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-sh@...r.kernel.org
Subject: Re: [PATCH 1/4] clk: Add a generic clock infrastructure

On Fri, 20 May 2011, Sascha Hauer wrote:

> Hi Jeremy,
> 
> Nice to see progress in this area :)
> 
> On Fri, May 20, 2011 at 03:27:49PM +0800, Jeremy Kerr wrote:
> > +
> > +struct clk *clk_register(struct clk_hw_ops *ops, struct clk_hw *hw,
> > +		const char *name)
> > +{
> > +	struct clk *clk;
> > +
> > +	clk = kzalloc(sizeof(*clk), GFP_KERNEL);
> > +	if (!clk)
> > +		return NULL;
> > +
> > +	clk->name = name;
> > +	clk->ops = ops;
> > +	clk->hw = hw;
> > +	hw->clk = clk;
> 
> is it worth to add a CLK_REGISTERED flag here? Up to now clocks do not
> have to be registered at all and the registering might be forgotten for
> some clocks. I suppose funny things can happen when we operate on
> unregistered clocks.

No, because not registered clocks are not accessible :)

 > +
> > +	/* Query the hardware for parent and initial rate */
> > +
> > +	if (clk->ops->get_parent)
> > +		/* We don't to lock against prepare/enable here, as
> > +		 * the clock is not yet accessible from anywhere */
> > +		clk->parent = clk->ops->get_parent(clk->hw);
> > +
> > +	if (clk->ops->recalc_rate)
> > +		clk->rate = clk->ops->recalc_rate(clk->hw);
> 
> This implicitely requires that we never register a clock before its
> parent is registered. This makes perfect sense but I think we should
> catch it here when the user tries to register a clock with a not yet
> registered parent.

We can agree on that, but we can make it more clever than that.
 
> > +
> > +
> > +	return clk;
> > +}
> > +EXPORT_SYMBOL_GPL(clk_register);
> 
> BTW we planned to let the linker do the job of registering static
> clocks, but this is only convenience and can be added later.

Right, you just need a helper function which runs through the list of
static stuff.

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