[lkml]   [2020]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH] thermal: doc: Add cooling device documentation to Sphinx TOC tree
This patch adds cpu-idle-cooling.rst into Sphinx TOC tree and fixes
some warnings and style issues.

Signed-off-by: Changbin Du <>
.../driver-api/thermal/cpu-idle-cooling.rst | 27 ++++++++++---------
Documentation/driver-api/thermal/index.rst | 1 +
2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/Documentation/driver-api/thermal/cpu-idle-cooling.rst b/Documentation/driver-api/thermal/cpu-idle-cooling.rst
index 9f0016ee4cfb..698fcadbecee 100644
--- a/Documentation/driver-api/thermal/cpu-idle-cooling.rst
+++ b/Documentation/driver-api/thermal/cpu-idle-cooling.rst
@@ -1,6 +1,9 @@
+CPU Idle Cooling


Under certain circumstances a SoC can reach a critical temperature
limit and is unable to stabilize the temperature around a temperature
@@ -24,8 +27,8 @@ with a power less than the requested power budget and the next OPP
exceeds the power budget. An intermediate OPP could have been used if
it were present.


If we can remove the static and the dynamic leakage for a specific
duration in a controlled period, the SoC temperature will
@@ -45,12 +48,12 @@ idle state target residency, we lead to dropping the static and the
dynamic leakage for this period (modulo the energy needed to enter
this state). So the sustainable power with idle cycles has a linear
relation with the OPP’s sustainable power and can be computed with a
-coefficient similar to:
+coefficient similar to::

Power(IdleCycle) = Coef x Power(OPP)

-Idle Injection:
+Idle Injection

The base concept of the idle injection is to force the CPU to go to an
idle state for a specified time each control cycle, it provides
@@ -136,7 +139,7 @@ Power considerations

When we reach the thermal trip point, we have to sustain a specified
-power for a specific temperature but at this time we consume:
+power for a specific temperature but at this time we consume::

Power = Capacitance x Voltage^2 x Frequency x Utilisation

@@ -145,7 +148,7 @@ wrong in the system setup). The ‘Capacitance’ and ‘Utilisation’ are a
fixed value, ‘Voltage’ and the ‘Frequency’ are fixed artificially
because we don’t want to change the OPP. We can group the
‘Capacitance’ and the ‘Utilisation’ into a single term which is the
-‘Dynamic Power Coefficient (Cdyn)’ Simplifying the above, we have:
+‘Dynamic Power Coefficient (Cdyn)’ Simplifying the above, we have::

Pdyn = Cdyn x Voltage^2 x Frequency

@@ -154,7 +157,7 @@ in order to target the sustainable power defined in the device
tree. So with the idle injection mechanism, we want an average power
(Ptarget) resulting in an amount of time running at full power on a
specific OPP and idle another amount of time. That could be put in a

P(opp)target = ((Trunning x (P(opp)running) + (Tidle x P(opp)idle)) /
(Trunning + Tidle)
@@ -165,7 +168,7 @@ equation:

At this point if we know the running period for the CPU, that gives us
the idle injection we need. Alternatively if we have the idle
-injection duration, we can compute the running duration with:
+injection duration, we can compute the running duration with::

Trunning = Tidle / ((P(opp)running / P(opp)target) - 1)

@@ -188,7 +191,7 @@ However, in this demonstration we ignore three aspects:
target residency, otherwise we end up consuming more energy and
potentially invert the mitigation effect

-So the final equation is:
+So the final equation is::

Trunning = (Tidle - Twakeup ) x
(((P(opp)dyn + P(opp)static ) - P(opp)target) / P(opp)target )
diff --git a/Documentation/driver-api/thermal/index.rst b/Documentation/driver-api/thermal/index.rst
index 5ba61d19c6ae..4cb0b9b6bfb8 100644
--- a/Documentation/driver-api/thermal/index.rst
+++ b/Documentation/driver-api/thermal/index.rst
@@ -8,6 +8,7 @@ Thermal
:maxdepth: 1

+ cpu-idle-cooling

 \ /
  Last update: 2020-02-04 14:00    [W:0.061 / U:0.280 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site