openbmc/phosphor-pid-control/README.md

1 # phosphor-pid-control
3 This is a daemon running within the OpenBMC environment. It uses a well-defined
4 configuration file to control the temperature of the tray components to keep
5 them within operating conditions. It may require coordination with host-side
10 The BMC will run a daemon that controls the fans by pre-defined zones. The
11 application will use thermal control, such that each defined zone is kept within
13 sensors as well as host-provided information over an IPMI OEM command.
21 The system will run a control loop for each zone with the attempt to maintain
26 [How to configure phosphor-pid-control](configure.md)
30 The software will run as a multi-threaded daemon that runs a control loop for
38 phosphor-hwmon are laid out.
54 ### IPMI Access to Phosphor-pid-control
56 [OEM-IPMI Definitions](ipmi.md)
79 This will receive an update from phosphor-hwmon each time it updates any sensor
82 By default phosphor-hwmon reads each sensor in turn and then sleeps for 1
83 second. We'll be updating phosphor-hwmon to sleep for a shorter period -- how
84 short though is still TBD. We'll also be updating phosphor-hwmon to support pwm
87 ### Thermal Control Loops
89 Each zone will require a control loop that monitors the associated thermals and
94 the system to its knees -- in that all CPU cycles would be spent reading the
105 By default, swampd won't log information. To enable logging pass "-l" on the
110 To enable tuning, pass "-t" on the command line.
118 - `dbus` - Any read or write interface that uses dbus primarily.
119 - `experiments` - Small execution paths that allow for fan examination including
121 - `ipmi` - Manual control for any zone is handled by receiving an IPMI message.
124 - `notimpl` - These are read-only and write-only interface implementations that
126 - `pid` - This contains all the PID associated code, including the zone
128 - `scripts` - This contains the scripts that convert YAML into C++.
129 - `sensors` - This contains a couple of sensor types including the pluggable
131 - `sysfs` - This contains code that reads from or writes to sysfs.
132 - `threads` - Most of swampd's threads run in this method where there's just a
137 ### Two Margin Sensors Into Three Fans (Non-Step PID)
145 fleeting0+---->+-------+    +-------+     Thermal PID sampled
146                |  min()+--->+  PID  |     slower rate.
147 fleeting1+---->+-------+    +---+---+
152                              +--+-----+
153   The Fan PID        fan0+--->        |  New PWM  +-->fan0
155   faster rate        fan1+--->  PID   +---------->--->fan1
157   fans.              fan2+--->        |           +-->fan2
158                        ^     +--------+                +
160                        +-------------------------------+