Resource: LCE13 Name: Thermal Management BOF Date: 09-07-2013 Speaker: Sanjay Singh Rawat (Linaro/LG Electronics and Amit Kucheria (Linaro Video: http://youtu.be/PLOgFY37PsQ

1. Sanjay Singh Rawat (Linaro/LG Electronics)
Amit Kucheria (Linaro)
Thermal Management BoF

2. Content
 General Thermal Framework (Intel)
 Governors (Intel)
 Possible solutions

3.  Sensor & Thermal Zone
sensor-1
Thermal core
sensor-2
Thermal
zone

4.  Cooling devices:
- SW (cpufreq_cooling)
- HW (fan, sink)

5. - Sensors <=> Thermal Zones
- registration
- trips levels
- operations
- bind
- temp/trend
- trip temp/type
- cooling device:
- state get/set

6.  Instance
Thermal
Instance
Thermal
zone Trip point Cooling
device
Cooling
State
levels

7.  Trip types:
- Active/Passive
Handling → governors
- Critical/Hot
Handling → shutdown/notify

8.  Flow:
irq
tzone-update
get-temp
handle-trip
Throttle/shutdown

9. tz 1
tz 2
tz n
t1-tz1
t2-tz1
t1-tz2
t1-tzn
cpufreq_cool
cdev-n
tz- thermal zone
t- trip point
cdev- cooling device
Governor
Trip Type
Shutdown/Notify
instance
FAN
thermal-core
cooling_device

10.  Governors: (intel)
Step wise
Fair share
user space

11. Step Wise
 Trend for zone
THERMAL_TREND_STABLE
THERMAL_TREND_RAISING
THERMAL_TREND_DROPPING
THERMAL_TREND_RAISE_FULL
THERMAL_TREND_DROP_FULL
 throttle / temperature
 Target cooling state, range set during registering.
 Update to cooling device

12. Fair Share
 Multiple cooling devices. Weight/Effectiveness of Cooling
device(w)
 Max states (m)
 Trip Level (l)
 Target state = (w * l * m) / (100 * total_trip_no)
 Update to cooling device state
User space
 user side management provision

13.  Cpufreq Cooling (by Amit D Kachhap)
 Scaling frequency to achieve the target set by the
Governor
Contribution by Linaro:

14. Future Solutions/Issues:
 Coordination with scheduler to limit load on cpu with high
temperature/idle injection?
 Limitation of maximum 12 trip points for thermal zone.
 GPU cooling?
 Shared cooling device conflict?
 More generic cooling devices