lkml.org 
[lkml]   [2020]   [Apr]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] thermal: core: Send a sysfs notification on trip points
On Thu, Apr 02, 2020 at 04:21:15PM +0200, Daniel Lezcano wrote:
> Currently the userspace has no easy way to get notified when a
> specific trip point was crossed. There are a couple of approaches:
>
> - the userspace polls the sysfs temperature with usually an
> unacceptable delay between the trip temperature point crossing and
> the moment it is detected, or a high polling rate with an
> unacceptable number of wakeup events.
>
> - the thermal zone is set to be managed by an userspace governor in
> order to receive the uevent even if the thermal zone needs to be
> managed by another governor.
>
> These changes allow to send a sysfs notification on the
> trip_point_*_temp when the temperature is getting higher than the trip
> point temperature. By this way, the userspace can be notified
> everytime when the trip point is crossed, this is useful for the
> thermal Android HAL or for notification to be sent via d-bus.
>
> That allows the userspace to manage the applications based on specific
> alerts on different thermal zones to mitigate the skin temperature,
> letting the kernel governors handle the high temperature for hardware
> like the CPU, the GPU or the modem.
>
> The temperature can be oscillating around a trip point and the event
> will be sent multiple times. It is up to the userspace to deal with
> this situation.

The actual temperature value would also be interesting. Is there a way
for userspace to obtain it in a race-free manner when it is notified
that the trip point has been crossed?

> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index c06550930979..3cbdd20252ab 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -407,6 +407,19 @@ static void handle_critical_trips(struct thermal_zone_device *tz,
> }
> }
>
> +static int thermal_trip_crossed(struct thermal_zone_device *tz, int trip)
> +{
> + int trip_temp;
> +
> + tz->ops->get_trip_temp(tz, trip, &trip_temp);
> +
> + if (tz->last_temperature == THERMAL_TEMP_INVALID)
> + return 0;
> +
> + return ((tz->last_temperature < trip_temp)) &&
> + (tz->temperature >= trip_temp));

drivers/thermal/thermal_core.c: In function ‘thermal_trip_crossed’:
drivers/thermal/thermal_core.c:425:33: error: expected ‘;’ before ‘)’ token
(tz->temperature >= trip_temp));
^
drivers/thermal/thermal_core.c:425:33: error: expected statement before ‘)’ token

> +}
> +
> static void handle_thermal_trip(struct thermal_zone_device *tz, int trip)
> {
> enum thermal_trip_type type;
> @@ -417,6 +430,16 @@ static void handle_thermal_trip(struct thermal_zone_device *tz, int trip)
>
> tz->ops->get_trip_type(tz, trip, &type);
>
> + /*
> + * This condition will be true everytime the temperature is
> + * greater than the trip point and the previous temperature
> + * was below. In this case notify the userspace via a sysfs
> + * event on the trip point.
> + */
> + if (thermal_trip_crossed(tz, trip))
> + sysfs_notify(&tz->device.kobj, NULL,
> + tz->trip_temp_attrs[trip].attr.attr.name);

Normally sysfs_notify() is used to notify userspace that the value of
the sysfs file has changed, but in this case it's being used on a sysfs
file whose value never changes. I don't know if there are other drivers
that do something similar.

\
 
 \ /
  Last update: 2020-04-03 16:40    [W:0.057 / U:0.356 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site