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

On Fri, Feb 4, 2011 at 7:48 PM, Russell King - ARM Linux
[off-list ref] 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.