diff options
| author | Lukasz Luba <lukasz.luba@arm.com> | 2020-11-03 09:05:58 +0000 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2020-11-10 20:29:28 +0100 |
| commit | 5a64f775691647c242aa40d34f3512e7b179a921 (patch) | |
| tree | 469e6eeb2e64d129f0b2242084875081e65ef4ab /Documentation/driver-api/thermal | |
| parent | c250d50fe2ce627ca9805d9c8ac11cbbf922a4a6 (diff) | |
| download | linux-5a64f775691647c242aa40d34f3512e7b179a921.tar.bz2 | |
PM: EM: Clarify abstract scale usage for power values in Energy Model
The Energy Model (EM) can store power values in milli-Watts or in abstract
scale. This might cause issues in the subsystems which use the EM for
estimating the device power, such as:
- mixing of different scales in a subsystem which uses multiple
(cooling) devices (e.g. thermal Intelligent Power Allocation (IPA))
- assuming that energy [milli-Joules] can be derived from the EM power
values which might not be possible since the power scale doesn't have
to be in milli-Watts
To avoid misconfiguration add the requisite documentation to the EM and
related subsystems: EAS and IPA.
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/driver-api/thermal')
| -rw-r--r-- | Documentation/driver-api/thermal/power_allocator.rst | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/Documentation/driver-api/thermal/power_allocator.rst b/Documentation/driver-api/thermal/power_allocator.rst index 67b6a3297238..aa5f66552d6f 100644 --- a/Documentation/driver-api/thermal/power_allocator.rst +++ b/Documentation/driver-api/thermal/power_allocator.rst @@ -71,7 +71,9 @@ to the speed-grade of the silicon. `sustainable_power` is therefore simply an estimate, and may be tuned to affect the aggressiveness of the thermal ramp. For reference, the sustainable power of a 4" phone is typically 2000mW, while on a 10" tablet is around 4500mW (may vary -depending on screen size). +depending on screen size). It is possible to have the power value +expressed in an abstract scale. The sustained power should be aligned +to the scale used by the related cooling devices. If you are using device tree, do add it as a property of the thermal-zone. For example:: @@ -269,3 +271,11 @@ won't be very good. Note that this is not particular to this governor, step-wise will also misbehave if you call its throttle() faster than the normal thermal framework tick (due to interrupts for example) as it will overreact. + +Energy Model requirements +========================= + +Another important thing is the consistent scale of the power values +provided by the cooling devices. All of the cooling devices in a single +thermal zone should have power values reported either in milli-Watts +or scaled to the same 'abstract scale'. |