[2/2] hwmon: (amd_energy) Add documentation

Commit Message

Naveen Krishna Chatradhi April 9, 2020, 3:39 p.m. UTC

Document amd_energy driver with all chips supported by it.

Cc: Guenter Roeck <[e-mail]>
Signed-off-by: Naveen Krishna Chatradhi <[e-mail]>
---
 Documentation/hwmon/amd_energy.rst | 78 ++++++++++++++++++++++++++++++++++++++
 Documentation/hwmon/index.rst      |  1 +
 2 files changed, 79 insertions(+)
 create mode 100644 Documentation/hwmon/amd_energy.rst

Patch

diff --git a/Documentation/hwmon/amd_energy.rst b/Documentation/hwmon/amd_energy.rst
new file mode 100644
index 000000000000..516694d3c1e0
--- /dev/null
+++ b/Documentation/hwmon/amd_energy.rst
@@ -0,0 +1,78 @@ 
+Kernel driver amd_energy
+==========================
+
+Supported chips:
+
+* AMD Family 17h Processors
+
+  Prefix: 'amd_energy'
+
+  Addresses used:  RAPL MSRs
+
+  Datasheets:
+
+  - Processor Programming Reference (PPR) for
+        AMD Family 17h Model 01h, Revision B1 Processors
+  - Preliminary Processor Programming Reference (PPR) for
+        AMD Family 17h Model 31h, Revision B0 Processors
+
+Author: Naveen Krishna Chatradhi <[e-mail]>
+
+Description
+-----------
+
+The Energy driver exposes the energy counters that are
+reported via the Running Average Power Limit (RAPL)
+Model-specific Registers (MSRs) via the hardware monitor
+(HWMON) sysfs interface.
+
+1. Power, Energy and Time Units
+  * MSR_RAPL_POWER_UNIT/ C001_0299:
+    -> 32-bit(RO), Configured in BIOS
+    -> shared with all cores in the socket
+
+  * A sysfs entry "energy_units" is created to show the
+    [ESU] energy units in joules
+
+2. Energy consumed by each Core
+  * MSR_CORE_ENERGY_STATUS/ C001_029A:
+    -> 32-bitRO, Accumulator, core-level power reporting
+
+  * A sysfs entry "core_energy%d_input" for each core is
+    created to show the core energy counter value.
+
+3. Energy consumed by Socket
+  * MSR_PACKAGE_ENERGY_STATUS/ C001_029B:
+    -> 32-bitRO, Accumulator, socket-level power reporting,
+    -> shared with all cores in socket
+
+  * A sysfs entry "socket_energy%d_input" for each socket
+    is created to show the socket energy counter value.
+
+Energy Caluclation:
+
+Energy information (in Joules) is based on the multiplier,
+1/2^ESU; where ESU is an unsigned integer read from
+MSR_RAPL_POWER_UNIT register. Default value is 10000b,
+indicating energy status unit is 15.3 micro-Joules increment.
+
+These registers are updated every 1ms and cleared on
+reset of the system.
+
+Users calculate power for a given domain by calculating
+	dEnergy/dTime for that domain.
+
+Sysfs attributes
+----------------
+
+======================= =================================
+
+core_energy[N]_input	Measured input core energy
+			[one sysfs entry for each core]
+
+socket_energy[N]_input	Measured input socket energy
+			[one sysfs entry for each socket]
+
+energy_units		ESU Energy Status Units.
+
+======================= ==================================
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 8ef62fd39787..fc4b89810e67 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -39,6 +39,7 @@  Hardware Monitoring Kernel Drivers
    adt7470
    adt7475
    amc6821
+   amd_energy
    asb100
    asc7621
    aspeed-pwm-tacho