linux-kernel - Re: [RFC, PATCH 3/3] clk: add warnings for incorrect enable/prepare semantics

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Message-ID: <20110210093756.GA24710@b20223-02.ap.freescale.net>
Date:	Thu, 10 Feb 2011 17:37:57 +0800
From:	Richard Zhao <richard.zhao@...escale.com>
To:	Jeremy Kerr <jeremy.kerr@...onical.com>
CC:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	<linux-sh@...r.kernel.org>,
	Ben Herrenschmidt <benh@...nel.crashing.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Paul Mundt <lethal@...ux-sh.org>,
	Dima Zavin <dmitriyz@...gle.com>,
	Saravana Kannan <skannan@...eaurora.org>,
	Ben Dooks <ben-linux@...ff.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [RFC, PATCH 3/3] clk: add warnings for incorrect
 enable/prepare semantics

Hi Jeremy,

On Wed, Feb 09, 2011 at 02:41:33PM +0800, Jeremy Kerr wrote:
> This change adds warnings to check for:
> 
>  1) enabling a clock that hasn't been prepared; and
> 
>  2) unpreparing a clock that is still enabled
> 
> While the correctness can't be guaranteed, the warnings should cover
> most situations, and won't indicate false positives.
> 
> Signed-off-by: Jeremy Kerr <jeremy.kerr@...onical.com>
> 
> ---
>  drivers/clk/clk.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index bbbdb0d..8c96623 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -29,6 +29,8 @@ EXPORT_SYMBOL_GPL(clk_prepare);
>  
>  void clk_unprepare(struct clk *clk)
>  {
> +	WARN_ON(clk->enable_count != 0);
> +
Other drivers may be using the clock and increased the enable_count.
This check may be moved to where we actually do unprepare.

Thanks
Richard
>  	mutex_lock(&clk->prepare_lock);
>  
>  	WARN_ON(clk->prepare_count == 0);
> @@ -45,6 +47,8 @@ int clk_enable(struct clk *clk)
>  	unsigned long flags;
>  	int ret = 0;
>  
> +	WARN_ON(clk->prepare_count == 0);
> +
>  	spin_lock_irqsave(&clk->enable_lock, flags);
>  	if (clk->enable_count == 0 && clk->ops->enable)
>  		ret = clk->ops->enable(clk);
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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