Locking in the clk API, part 2: clk_prepare/clk_unprepare

[Jassi Brar]

On Fri, Feb 4, 2011 at 7:48 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:

> int clk_enable(struct clk *clk)
> {
>        unsigned long flags;
>        int ret = 0;
>
>        if (clk) {
>                if (WARN_ON(!clk->prepare_count))
>                        return -EINVAL;
>
>                spin_lock_irqsave(&clk->lock, flags);
>                if (clk->enable_count++ == 0)
>                        ret = clk->ops->enable(clk);
>                spin_unlock_irqrestore(&clk->lock, flags);
>        }
>        return ret;
> }
>
> is entirely sufficient to catch the case of a single-use clock not being
> prepared before clk_enable() is called.
>
> We're after detecting drivers missing calls to clk_prepare(), we're not
> after detecting concurrent calls to clk_prepare()/clk_unprepare().

I hope you mean 'making sure the clock is prepared before it's enabled
' rather than
'catching a driver that doesn't do clk_prepare before clk_enable'.
Because, the above implementation still doesn't catch a driver that
doesn't call clk_prepare
but simply uses a clock that happens to have been already prepare'd by
some other
driver or the platform.