Re: thermal governor: does it actually work??

Peter Feuerer
2013-02-18T16:47:38Z

Hi Boris, Hi Rui,

@Rui, would be great, if you could review the patch and verify, whether
everything I'm telling is the truth, thanks.

Borislav Petkov writes:

> On Sun, Feb 17, 2013 at 04:41:57PM +0100, Peter Feuerer wrote:
>> Don't think so, I think this was already in since 2.6.<something> and
>> I assume with this patch applied, acerhdf works from at least this
>> 2.6.<something> up to new 3.8 and will still work in the future.
>
> Well, it can't be because there wouldn't be breakage otherwise, right?
> I've been running 3.5 on the atom for a long time and it was ok but 3.8
> is showing the issue. So something *has* changed.

I think previous 3.7 were two methods possible, the method with one trippoint,
on which the state gets switched on and off using this code in thermal_sys.c:
1060 if (temp >= trip_temp)
1061 cdev->ops->set_cur_state(cdev, 1);
1062 else
1063 cdev->ops->set_cur_state(cdev, 0);

And the other method with all the different trip points, which is used after
applying my patch.
The older way has been removed intentionally or not, I don't know. But as
acerhdf was depending on this old way, it stopped working.

> But, as you say above, I guess the two-point scheme of acerhdf doesn't
> have a governor that fits. So maybe the correct solution is to have an
> "on_off" stupid governor which gets used by acerhdf and does simply call
> into acerhdf to switch on the fan to auto above a specified trip point.
>
> It could be a lot of overhead for nothing in the end, though.

I think adding a two-point governor would maybe be the somehow cleaner way...
Rui, what do you think, is there a way, you could provide a two-point governor
with upper temperature for turning on the fan and a lower temperature for
turning it off again?

>> >Maybe the critical and hot types need to go here? I.e., 3 and 4?
>>
>> Yes, crit has to go there.
>
> Right, I'll wait for that version of the patch to test. :)

I added crit to the patch below.

>From 74af34f3099828d5c7c2b4fd4ccf445edfdc6f1e Mon Sep 17 00:00:00 2001
From: Peter Feuerer <peter@piie.net>
Date: Mon, 18 Feb 2013 17:23:34 +0100
Subject: [PATCH] added three more trip points to acerhdf, this allows thermal
layer to correctly handle the two point regulation of acerhdf. Trip point 0
will be active from 0 degree to "fanoff" and is marked as passive, then trip
point 1 is valid from "fanoff" to "fanon" value and is marked as active, even
if it's only really active in case temperature is going down from trip point
2. Trip point 2 will be valid above "fanon" value and is also marked as
active. Trip point 3 is when hitting the critical temperature.

---
drivers/platform/x86/acerhdf.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/acerhdf.c b/drivers/platform/x86/acerhdf.c
index f94467c..b121449 100644
--- a/drivers/platform/x86/acerhdf.c
+++ b/drivers/platform/x86/acerhdf.c
@@ -400,7 +400,13 @@ static int acerhdf_get_trip_type(struct thermal_zone_device *thermal, int trip,
enum thermal_trip_type *type)
{
if (trip == 0)
+ *type = THERMAL_TRIP_PASSIVE;
+ if (trip == 1)
*type = THERMAL_TRIP_ACTIVE;
+ if (trip == 2)
+ *type = THERMAL_TRIP_ACTIVE;
+ if (trip == 3)
+ *type = THERMAL_TRIP_CRITICAL;

return 0;
}
@@ -409,7 +415,13 @@ static int acerhdf_get_trip_temp(struct thermal_zone_device *thermal, int trip,
unsigned long *temp)
{
if (trip == 0)
+ *temp = 0;
+ if (trip == 1)
+ *temp = fanoff;
+ if (trip == 2)
*temp = fanon;
+ if (trip == 3)
+ *temp = ACERHDF_TEMP_CRIT;

return 0;
}
@@ -431,6 +443,7 @@ static struct thermal_zone_device_ops acerhdf_dev_ops = {
.get_trip_type = acerhdf_get_trip_type,
.get_trip_temp = acerhdf_get_trip_temp,
.get_crit_temp = acerhdf_get_crit_temp,
+ .notify = NULL,
};

@@ -486,7 +499,8 @@ static int acerhdf_set_cur_state(struct thermal_cooling_device *cdev,
(cur_temp < fanoff))
acerhdf_change_fanstate(ACERHDF_FAN_OFF);
} else {
- if (cur_state == ACERHDF_FAN_OFF)
+ if ((cur_state == ACERHDF_FAN_OFF) &&
+ (cur_temp > fanon))
acerhdf_change_fanstate(ACERHDF_FAN_AUTO);
}
return 0;
@@ -661,8 +675,9 @@ static int acerhdf_register_thermal(void)
if (IS_ERR(cl_dev))
return -EINVAL;

- thz_dev = thermal_zone_device_register("acerhdf", 1, 0, NULL,
- &acerhdf_dev_ops, NULL, 0,
+ thz_dev = thermal_zone_device_register("acerhdf", 4, 0, NULL,
+ &acerhdf_dev_ops,
+ (kernelmode) ? interval*1000 : 0,
(kernelmode) ? interval*1000 : 0);
if (IS_ERR(thz_dev))
return -EINVAL;
--
1.8.1.3