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diff --git a/Documentation/hwmon/sbrmi.rst b/Documentation/hwmon/sbrmi.rst new file mode 100644 index 000000000000..296049e13ac9 --- /dev/null +++ b/Documentation/hwmon/sbrmi.rst @@ -0,0 +1,79 @@ +.. 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 <akshay.gupta@amd.com> + +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 |