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

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Date:	Mon, 4 Jan 2016 11:22:26 +0000
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	Leo Yan <leo.yan@...aro.org>,
	Eduardo Valentin <edubezval@...il.com>
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 01/01/16 00:03, Leo Yan wrote:
> Hi Eduardo,
>
> Thanks for review.
>
> On Thu, Dec 31, 2015 at 09:21:26AM -0800, Eduardo Valentin wrote:
>> 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.
>
> Okay, I will try to update these properties in power_allocator.c.
> Javi, do you think this is fine for you?

If sustainable power were to change frequently (perhaps on entry/exit of 
a fan inhibitor mode?) then we would accumulate rounding errors here...





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