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:

Author: Akshay Gupta <>


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.


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
Adapter: bcm2835 I2C adapter
power1:       61.00 W (cap = 225.00 W)

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