linux-kernel - Re: [PATCH] arm: mxc: utilise usecount field in clock operations

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Date:	Thu, 22 Apr 2010 13:56:23 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Amit Kucheria <amit.kucheria@...onical.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm: mxc: utilise usecount field in clock operations

On Wed, Apr 21, 2010 at 09:37:31PM +0300, Amit Kucheria wrote:
> clk->usecount can be used by platform code to check if a clock is active or
> not.

The patch seems mostly fine but the commit log not. How about something like
'This patch fixes the clock refcounting when reparenting is used.'

A reference to

http://www.spinics.net/lists/arm-kernel/msg85879.html

might help aswell.

> 
> Signed-off-by: Amit Kucheria <amit.kucheria@...onical.com>
> ---
>  arch/arm/plat-mxc/clock.c |   37 ++++++++++++++++++++++++-------------
>  1 files changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
> index 323ff8c..c791f38 100644
> --- a/arch/arm/plat-mxc/clock.c
> +++ b/arch/arm/plat-mxc/clock.c
> @@ -50,15 +50,15 @@ static DEFINE_MUTEX(clocks_mutex);
>  
>  static void __clk_disable(struct clk *clk)
>  {
> -	if (clk == NULL || IS_ERR(clk))
> +	if (clk == NULL || IS_ERR(clk) || !clk->usecount)
>  		return;
>  
> -	__clk_disable(clk->parent);
> -	__clk_disable(clk->secondary);
> -
> -	WARN_ON(!clk->usecount);
> -	if (!(--clk->usecount) && clk->disable)
> -		clk->disable(clk);
> +	if (!(--clk->usecount)) {
> +		if (clk->disable)
> +			clk->disable(clk);
> +		__clk_disable(clk->parent);
> +		__clk_disable(clk->secondary);
> +	}
>  }
>  
>  static int __clk_enable(struct clk *clk)
> @@ -66,12 +66,13 @@ static int __clk_enable(struct clk *clk)
>  	if (clk == NULL || IS_ERR(clk))
>  		return -EINVAL;
>  
> -	__clk_enable(clk->parent);
> -	__clk_enable(clk->secondary);
> -
> -	if (clk->usecount++ == 0 && clk->enable)
> -		clk->enable(clk);
> +	if (clk->usecount++ == 0) {
> +		__clk_enable(clk->parent);
> +		__clk_enable(clk->secondary);
>  
> +		if (clk->enable)
> +			clk->enable(clk);
> +	}
>  	return 0;
>  }
>  
> @@ -160,17 +161,27 @@ EXPORT_SYMBOL(clk_set_rate);
>  int clk_set_parent(struct clk *clk, struct clk *parent)
>  {
>  	int ret = -EINVAL;
> +	struct clk *prev_parent = clk->parent;
>  
>  	if (clk == NULL || IS_ERR(clk) || parent == NULL ||
>  	    IS_ERR(parent) || clk->set_parent == NULL)
>  		return ret;
>  
> +	if (clk->usecount != 0) {
> +		clk_enable(parent);
> +	}
> +
>  	mutex_lock(&clocks_mutex);
>  	ret = clk->set_parent(clk, parent);
> -	if (ret == 0)
> +	if (ret == 0) {
>  		clk->parent = parent;
> +	}

Please remove this hunk. It does not change anything except violating
the coding style. Also, please remove unnecessary braces.

>  	mutex_unlock(&clocks_mutex);
>  
> +	if (clk->usecount != 0) {
> +		clk_disable(prev_parent);
> +	}
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL(clk_set_parent);
> -- 
> 1.7.0.4
> 
> 

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