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- .. SPDX-License-Identifier: GPL-2.0-or-later
- Kernel driver sbrmi
- ===================
- Supported hardware:
- * Sideband Remote Management Interface (SB-RMI) compliant AMD SoC
- device connected to the BMC via the APML.
- Prefix: 'sbrmi'
- Addresses scanned: This driver doesn't support address scanning.
- To instantiate this driver on an AMD CPU with SB-RMI
- support, the i2c bus number would be the bus connected from the board
- management controller (BMC) to the CPU.
- The SMBus address is really 7 bits. Some vendors and the SMBus
- specification show the address as 8 bits, left justified with the R/W
- bit as a write (0) making bit 0. Some vendors use only the 7 bits
- to describe the address.
- As mentioned in AMD's APML specification, The SB-RMI address is
- normally 78h(0111 100W) or 3Ch(011 1100) for socket 0 and 70h(0111 000W)
- or 38h(011 1000) for socket 1, but it could vary based on hardware
- address select pins.
- Datasheet: The SB-RMI interface and protocol along with the Advanced
- Platform Management Link (APML) Specification is available
- as part of the open source SoC register reference at:
- https://www.amd.com/en/support/tech-docs?keyword=55898
- Author: Akshay Gupta <[email protected]>
- Description
- -----------
- The APML provides a way to communicate with the SB Remote Management interface
- (SB-RMI) module from the external SMBus master that can be used to report socket
- power on AMD platforms using mailbox command and resembles a typical 8-pin remote
- power sensor's I2C interface to BMC.
- This driver implements current power with power cap and power cap max.
- sysfs-Interface
- ---------------
- Power sensors can be queried and set via the standard ``hwmon`` interface
- on ``sysfs``, under the directory ``/sys/class/hwmon/hwmonX`` for some value
- of ``X`` (search for the ``X`` such that ``/sys/class/hwmon/hwmonX/name`` has
- content ``sbrmi``)
- ================ ===== ========================================================
- Name Perm Description
- ================ ===== ========================================================
- power1_input RO Current Power consumed
- power1_cap RW Power limit can be set between 0 and power1_cap_max
- power1_cap_max RO Maximum powerlimit calculated and reported by the SMU FW
- ================ ===== ========================================================
- The following example show how the 'Power' attribute from the i2c-addresses
- can be monitored using the userspace utilities like ``sensors`` binary::
- # sensors
- sbrmi-i2c-1-38
- Adapter: bcm2835 I2C adapter
- power1: 61.00 W (cap = 225.00 W)
- sbrmi-i2c-1-3c
- Adapter: bcm2835 I2C adapter
- power1: 28.39 W (cap = 224.77 W)
- #
- Also, Below shows how get and set the values from sysfs entries individually::
- # cat /sys/class/hwmon/hwmon1/power1_cap_max
- 225000000
- # echo 180000000 > /sys/class/hwmon/hwmon1/power1_cap
- # cat /sys/class/hwmon/hwmon1/power1_cap
- 180000000
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