Openpower based Inband OCC sensors
===================================

In POWER8, OCC (On-Chip-Controller) periodically  reads various
sensors related to power, temperature, CPU frequency, CPU utilization,
memory bandwidth etc., These sensor data is stored in OCC's SRAM and
is available to user via 'ipmitool sdr' and AMESTER. Currently AMESTER
is available only out-of-band and ipmitool is slow and not favourable
for profiling. So this method provides a faster inband sensing
mechanism from linux kernel to read sensors and profile workloads at
sub-millisecond granularity.

Inband OCC sensor requires the below firmware changes:
1) OCC changes to write the sensor data periodically to main memory.
	https://github.com/shilpasri/occ/tree/inband-sensors
2) Skiboot changes to export this memory mapped sensor data as DT
entries to kernel.
	https://github.com/shilpasri/skiboot/tree/inband-sensors
3) Kernel requirements:
   - Latest upstream kernel with ibmpowernv.ko
     (hwmon driver CONFIG_SENSORS_IBMPOWERNV)
   - Custom driver https://github.com/shilpasri/inband_sensors.git

Steps to build a PNOR image for inband-occ-sensors
===================================================
git clone --recursive https://github.com/shilpasri/op-build.git
cd op-build
git checkout -b inband_sensors origin/inband_sensors
. op-build-env
op-build palmetto_defconfig && op-build

Reading the inband-occ-sensors
==============================
* Using lm-sensors to read the power numbers. Load the platfrom hwmon
  module ibmpowernv.ko.
  # sensors | grep power1
  power1:      424.00 W

* Using custom driver to read the sensors, this driver will export the
  sensors to sysfs path /sys/devices/system/cpu/occ_sensors/
  # cd /sys/devices/system/cpu/occ_sensors/
  # ls
  chip0  system
  # ls *
  chip0:
  chip-energy  chip-mbw  core1-temp  core2-temp  core3-temp
  core4-temp  core5-temp  core6-temp  core7-temp  core8-temp  power
  power-memory  power-vcs  power-vdd
  system:
  ambient-temperature  count  fan-power  fan-speed  gpu-power
  io-power  power  storage-power  system-energy