From mboxrd@z Thu Jan  1 00:00:00 1970
From: jeremy.kerr@canonical.com (Jeremy Kerr)
Date: Tue, 15 Feb 2011 09:36:25 +0800
Subject: [RFC,PATCH 1/3] Add a common struct clk
In-Reply-To: <4D52F73A.4010707@bluewatersys.com>
References: <1297233693.242364.862698430999.1.gpush@pororo>
	<4D52F73A.4010707@bluewatersys.com>
Message-ID: <201102150936.26110.jeremy.kerr@canonical.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi Ryan,

> > +int clk_enable(struct clk *clk)
> > +{
> > +	unsigned long flags;
> > +	int ret = 0;
> > +
> > +	spin_lock_irqsave(&clk->enable_lock, flags);
> 
> 	WARN_ON(clk->prepare_count == 0); ?

Added later, but yes.

> 
> > +	if (clk->enable_count == 0 && clk->ops->enable)
> > +		ret = clk->ops->enable(clk);
> 
> Does it make sense to have a clock with no enable function which still
> returns success from clk_enable? Do we have any platforms which have
> NULL clk_enable functions?

It does, yes. Driver code should be always be calling clk_enable before using 
a clock, regardless of the implementation (which it shouldn't have to care 
abut), and should abort their initialisation if the clk_enable() fails.

Some clocks are always running, so the enable op will be empty. This is not an 
error, so the driver is free to continue.

> I think that for enable/disable at least we should require platforms to
> provide functions and oops if they have failed to do so. In the rare
> case that a platform doesn't need to do anything for enable/disable they
> can just supply empty functions.

Sounds like useless boilerplate - it's not an error to not need 
enable/disable, so I don't see why we need to add extra effort to handle this 
case.

> > +/**
> > + * __clk_get - acquire a reference to a clock
> > + *
> > + * @clk: The clock to refcount
> > + *
> > + * Before a clock is returned from clk_get, this function should be
> > called + * to update any clock-specific refcounting.
> 
> This is a bit misleading. It's not "should be called", it "is called". I
> think you should just remove the documentation for __clk_get/__clk_put
> or move it into clk.c since the functions are only used internally by
> the common clock code.

It'd be nice to remove this from the header, but this means we'll need extern 
prototypes in clkdev.c. Might be a reasonable compromise though.


> > +/**
> > + * clk_prepare - prepare clock for atomic enabling.
> > + *
> > + * @clk: The clock to prepare
> > + *
> > + * Do any blocking initialisation on @clk, allowing the clock to be
> > later + * enabled atomically (via clk_enable). This function may sleep.
> 
> "Possibly blocking" as below?

Yep, will unify these (and spell "possibly" correctly :) )

Cheers,


Jeremy