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authorNaveen Krishna Chatradhi <nchatrad@amd.com>2020-05-19 21:20:10 +0530
committerGuenter Roeck <linux@roeck-us.net>2020-05-22 06:28:39 -0700
commitb968279625a95fc6ae544713282c28a56a50d37e (patch)
treeb1064798740e00d97586d0efa400c84424c4fd9f /Documentation/hwmon
parent8abee9566b7e8eecf566c4daf6be062a27369890 (diff)
hwmon: (amd_energy) Add documentation
Document amd_energy driver with energy sensors supported by it. Cc: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Naveen Krishna Chatradhi <nchatrad@amd.com> Link: https://lore.kernel.org/r/20200519155011.56184-2-nchatrad@amd.com Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Diffstat (limited to 'Documentation/hwmon')
-rw-r--r--Documentation/hwmon/amd_energy.rst109
-rw-r--r--Documentation/hwmon/index.rst1
2 files changed, 110 insertions, 0 deletions
diff --git a/Documentation/hwmon/amd_energy.rst b/Documentation/hwmon/amd_energy.rst
new file mode 100644
index 000000000000..f8288edff664
--- /dev/null
+++ b/Documentation/hwmon/amd_energy.rst
@@ -0,0 +1,109 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+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
+
+ https://developer.amd.com/wp-content/resources/55570-B1_PUB.zip
+
+ - Preliminary Processor Programming Reference (PPR) for AMD Family 17h Model 31h, Revision B0 Processors
+
+ https://developer.amd.com/wp-content/resources/56176_ppr_Family_17h_Model_71h_B0_pub_Rev_3.06.zip
+
+Author: Naveen Krishna Chatradhi <nchatrad@amd.com>
+
+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:
+ shared with all cores in the socket
+
+2. Energy consumed by each Core
+ MSR_CORE_ENERGY_STATUS/ C001_029A:
+ 32-bitRO, Accumulator, core-level power reporting
+
+3. Energy consumed by Socket
+ MSR_PACKAGE_ENERGY_STATUS/ C001_029B:
+ 32-bitRO, Accumulator, socket-level power reporting,
+ shared with all cores in socket
+
+These registers are updated every 1ms and cleared on
+reset of the system.
+
+Note: If SMT is enabled, Linux enumerates all threads as cpus.
+Since, the energy status registers are accessed at core level,
+reading those registers from the sibling threads would result
+in duplicate values. Hence, energy counter entries are not
+populated for the siblings.
+
+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.
+
+Reported values are scaled as per the formula
+
+scaled value = ((1/2^ESU) * (Raw value) * 1000000UL) in uJoules
+
+Users calculate power for a given domain by calculating
+ dEnergy/dTime for that domain.
+
+Energy accumulation
+--------------------------
+
+Current, Socket energy status register is 32bit, assuming a 240W
+2P system, the register would wrap around in
+
+ 2^32*15.3 e-6/240 * 2 = 547.60833024 secs to wrap(~9 mins)
+
+The Core energy register may wrap around after several days.
+
+To improve the wrap around time, a kernel thread is implemented
+to accumulate the socket energy counters and one core energy counter
+per run to a respective 64-bit counter. The kernel thread starts
+running during probe, wakes up every 100secs and stops running
+when driver is removed.
+
+A socket and core energy read would return the current register
+value added to the respective energy accumulator.
+
+Sysfs attributes
+----------------
+
+=============== ======== =====================================
+Attribute Label Description
+=============== ======== =====================================
+
+* For index N between [1] and [nr_cpus]
+
+=============== ======== ======================================
+energy[N]_input EcoreX Core Energy X = [0] to [nr_cpus - 1]
+ Measured input core energy
+=============== ======== ======================================
+
+* For N between [nr_cpus] and [nr_cpus + nr_socks]
+
+=============== ======== ======================================
+energy[N]_input EsocketX Socket Energy X = [0] to [nr_socks -1]
+ Measured input socket energy
+=============== ======== ======================================
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index df87ae15a1d4..fb51c7ce8b27 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