linux-kernel - Re: [PATCH v3] PM / OPP: discard duplicate OPPs

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Date:	Mon, 19 May 2014 08:08:23 -0500
From:	Nishanth Menon <nm@...com>
To:	Chander Kashyap <chander.kashyap@...aro.org>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:	<rjw@...ysocki.net>, <pavel@....cz>, <len.brown@...el.com>,
	<gregkh@...uxfoundation.org>, <viresh.kumar@...aro.org>,
	Chander Kashyap <k.chander@...sung.com>,
	Inderpal Singh <inderpal.s@...sung.com>
Subject: Re: [PATCH v3] PM / OPP: discard duplicate OPPs

On 05/16/2014 04:00 AM, Chander Kashyap wrote:
> From: Chander Kashyap <k.chander@...sung.com>
> 
> This patch detects the duplicate OPP entries and discards them
> 
> Signed-off-by: Chander Kashyap <k.chander@...sung.com>
> Signed-off-by: Inderpal Singh <inderpal.s@...sung.com>
> ---
>  Changes in v3:
> 	- Modify the commit log
>  Changes in v2:
> 	- Reorder check for duplicate opp
> 
>  drivers/base/power/opp.c |   13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> index ca521e1..973da78 100644
> --- a/drivers/base/power/opp.c
> +++ b/drivers/base/power/opp.c
> @@ -443,15 +443,24 @@ int dev_pm_opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
>  	new_opp->u_volt = u_volt;
>  	new_opp->available = true;
>  
> -	/* Insert new OPP in order of increasing frequency */
> +	/*
> +	 * Insert new OPP in order of increasing frequency
> +	 * and discard if already present
> +	 */
>  	head = &dev_opp->opp_list;
>  	list_for_each_entry_rcu(opp, &dev_opp->opp_list, node) {
> -		if (new_opp->rate < opp->rate)
> +		if (new_opp->rate <= opp->rate)
>  			break;
>  		else
>  			head = &opp->node;
>  	}
>  
> +	if (new_opp->rate == opp->rate) {
> +		mutex_unlock(&dev_opp_list_lock);
> +		kfree(new_opp);
> +		return 0;

IF we decide on ensuring that the OPP additions are done one time[1] -
then returning -EEXIST is appropriate here. we want to be able to
catch warnings of sequencing errors, and returning 0 is not the way to
do it.

> +	}
> +
>  	list_add_rcu(&new_opp->node, head);
>  	mutex_unlock(&dev_opp_list_lock);
>  
> 

[1] http://marc.info/?l=linux-pm&m=140034777229205&w=2

-- 
Regards,
Nishanth Menon
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