linux-kernel - Re: [PATCH v2] thermal: re-calculate k_po/k

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Date:	Thu, 31 Dec 2015 09:21:26 -0800
From:	Eduardo Valentin <edubezval@...il.com>
To:	Leo Yan <leo.yan@...aro.org>
Cc:	Zhang Rui <rui.zhang@...el.com>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, javi.merino@....com
Subject: Re: [PATCH v2] thermal: re-calculate k_po/k_pu when update
 sustainable power

On Wed, Dec 30, 2015 at 06:38:40PM +0800, Leo Yan wrote:
> k_po/k_pu are in essence ratio values compared with sustainable power.
> So when update sustainable power, we can recalculate k_po/k_pu simply
> with below formula:
> 
>                sustainable_power(new)
>     k_p(new) = ---------------------- * k_p(old)
>                sustainable_power(old)
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  drivers/thermal/thermal_core.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index d9e525c..223f8df 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -908,7 +908,7 @@ sustainable_power_store(struct device *dev, struct device_attribute *devattr,
>  			const char *buf, size_t count)
>  {
>  	struct thermal_zone_device *tz = to_thermal_zone(dev);
> -	u32 sustainable_power;
> +	u32 sustainable_power, old_val;
>  
>  	if (!tz->tzp)
>  		return -EIO;
> @@ -916,8 +916,12 @@ sustainable_power_store(struct device *dev, struct device_attribute *devattr,
>  	if (kstrtou32(buf, 10, &sustainable_power))
>  		return -EINVAL;
>  
> +	old_val = tz->tzp->sustainable_power;
> +
>  	tz->tzp->sustainable_power = sustainable_power;
>  
> +	tz->tzp->k_po = (tz->tzp->k_po * sustainable_power) / old_val;
> +	tz->tzp->k_pu = (tz->tzp->k_pu * sustainable_power) / old_val;

I believe this has to be done by the governor. These properties are
power_allocator specific. thermal_core should not really care about
them.

>  	return count;
>  }
>  static DEVICE_ATTR(sustainable_power, S_IWUSR | S_IRUGO, sustainable_power_show,
> -- 
> 1.9.1
> 
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