From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jassi Brar <jassisinghbrar@gmail.com>
Date: Fri, 04 Feb 2011 11:04:03 +0000
Subject: Re: Locking in the clk API, part 2: clk_prepare/clk_unprepare
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To: linux-arm-kernel@lists.infradead.org

On Fri, Feb 4, 2011 at 7:48 PM, Russell King - ARM Linux
<linux@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.