Ryzen SMU

N.B. Images above shows the potential capabilities of this driver, retrieved using the monitor_cpu utility. Other processors will require tweaking on the user's part or additional tools.

Ryzen SMU is a Linux kernel driver that exposes access to the SMU (System Management Unit) for certain AMD Ryzen Processors. Use at your own risk, the author takes no responsibility over potential damages that may result from the misuse of this driver or programs dependent upon it.

The following processor code names are supported:

• Colfax
• Renoir
• Picasso
• Matisse
• Castle Peak
• Raven Ridge
• Raven Ridge 2
• Summit Ridge
• Pinnacle Ridge
• Rembrandt
• Vermeer
• Vangogh
• Cezanne
• Milan
• Dali

In addition, for the following models, the power metrics/monitoring (PM) table (seen in screenshot) can also be accessed:

• Vermeer ( Ryzen 5000 Desktop Series )
• Matisse ( Ryzen 3000 Desktop Series )
• Cezanne ( Ryzen 5000[GE] APU Series )
• Renoir ( Ryzen 4000[UGHS] APU Series )
• Picasso ( Ryzen 3000[UGHS] APU Series )
• Raven Ridge ( Ryzen 2000[GEU] APU Series )
• Raven Ridge 2

When loaded, the driver exposes several files under sysfs which can only be read with root permissions (for obvious reasons) at the root path /sys/kernel/ryzen_smu_drv:

• drv_version
• version
• mp1_if_version
• codename
• smu_args
• mp1_smu_cmd
• smn
• rsmu_cmd (Not present on Rembrandt, Vangogh)

For supported PM table models where RSMU is also supported, the following files are additionally exposed:

• pm_table_version
• pm_table_size
• pm_table

Installation

The kernel module may be installed either by DKMS or manually building and inserting the module.

Be sure kernel headers, dev utilities such as gcc and make are installed beforehand.

Ubuntu / Debian

sudo apt install dkms git build-essential linux-headers-$(uname -r)
git clone https://gitlab.com/leogx9r/ryzen_smu.git
cd ryzen_smu

sudo make dkms-install

Arch Linux

Available on the AUR.

Install it using your AUR helper of choice, example:

yay -S ryzen_smu-dkms-git

Stand-alone Installation

The module may be built and inserted into the running kernel manually as follows:

git clone https://gitlab.com/leogx9r/ryzen_smu.git
cd ryzen_smu

make
sudo insmod ryzen_smu.ko

Auto-Loading On System Startup

Assuming you are using systemd, the kernel module may be loaded automatically upon system startup using modules-load.d by adding the module name to /etc/modules-load.d/<name>.conf

Example:

# /etc/modules-load.d/ryzen_smu.conf
# Load ryzen_smu driver upon startup
ryzen_smu

Confirming Module Works

Upon loading the module, you should see output in your dmesg window listing the SMU version:

# dmesg

...
[1091.154018] ryzen_smu: CPUID: family 0x17, model 0x71, stepping 0x0, package 0x2
[1091.154385] ryzen_smu: SMU v46.54.0
...

After which you can verify the existence of the sysfs files and attempt to read them:

# ls -lah /sys/kernel/ryzen_smu_drv
total 0
drwxr-xr-x  2 root root    0 May  7 03:01 ./
drwxr-xr-x 14 root root    0 May  7 03:01 ../
-r--------  1 root root 4.0K May  7 03:12 codename
-r--------  1 root root 4.0K May  7 03:12 drv_version
-r--------  1 root root 4.0K May  7 03:10 mp1_if_version
-rw-------  1 root root 4.0K May  7 03:10 mp1_smu_cmd
-r--------  1 root root 4.0K May  7 03:12 pm_table
-r--------  1 root root 4.0K May  7 03:12 pm_table_size
-r--------  1 root root 4.0K May  7 03:12 pm_table_version
-rw-------  1 root root 4.0K May  7 03:10 rsmu_cmd
-rw-------  1 root root 4.0K May  7 03:10 smn
-rw-------  1 root root 4.0K May  7 03:10 smu_args
-r--------  1 root root 4.0K May  7 03:01 version

# cat /sys/kernel/ryzen_smu_drv/version          
SMU v46.54.0

# cat /sys/kernel/ryzen_smu_drv/mp1_if_version
2

# cat /sys/kernel/ryzen_smu_drv/codename
4

# cat /sys/kernel/ryzen_smu_drv/drv_version
0.0.1

Following which, you can run the test.py script to verify that SMU and SMN functionality is working:

# python3 scripts/test.py
Retrieved SMU Version: v46.54.0
Processor Code Name: Matisse
PM Table: [Supported/Unsupported]
SMN Offset[0x50200]: 0x00001539

Everything seems to be working properly!

Explaining Sysfs Files

/sys/kernel/ryzen_smu_drv/drv_version

Lists the string-representation of the driver (and thus interface) version. For userspace applications, they should make sure this version is within the expected range.

/sys/kernel/ryzen_smu_drv/version

Lists the current SMU firmware version in relation to the currently installed AGESA.

The following are several lists of SMU to AGESA versions:

Note: This file returns a string encoded version represented by the "SMU Version" above.

/sys/kernel/ryzen_smu_drv/mp1_if_version

Lists the interface version for the MP1 mailbox.

This can range from v9 to v13 and is indicated by the following table:

Value	Interface Version
0	v9
1	v10
2	v11
3	v12
4	v13
5	Undefined

Note: This file returns a string representation of the "Value" field above.

/sys/kernel/ryzen_smu_drv/codename

Returns a numeric index containing the running processor's codename based on the following enumeration:

Hex	Decimal	Code Name
00h	0	Unknown
01h	1	Colfax
02h	2	Renoir
03h	3	Picasso
04h	4	Matisse
05h	5	Threadripper
06h	6	Castle Peak
07h	7	Raven Ridge
08h	8	Raven Ridge 2
09h	9	Summit Ridge
0Ah	10	Pinnacle Ridge
0Bh	11	Rembrandt
0Ch	12	Vermeer
0Dh	13	Vangogh
0Eh	14	Cezanne
0Fh	15	Milan
10h	16	Dali

Note: This file returns 2 characters of the 'Decimal' encoded index.

/sys/kernel/ryzen_smu_drv/rsmu_cmd or /sys/kernel/ryzen_smu_drv/mp1_smu_cmd

This file allows the user to initiate an RSMU or MP1 SMU request. It accepts either an 8-bit or 32-bit command ID that is platform-dependent.

When this file is read, it produces the result on the status of the operation, as a 32 bit little-endian encoded value.

The SMU returns the following possible values which indicate the result of a command execution:

Hex	Decimal	Explanation
00h	0	WAITING
01h	1	OK
FFh	255	FAILED
FEh	254	UNKNOWN COMMAND
FDh	253	REJECTED - PREREQUISITE UNMET
FCh	252	REJECTED - BUSY

In addition to this, several custom error codes are also implemented by the driver:

Hex	Decimal	Explanation
FBh	251	COMMAND TIMEOUT
FAh	250	INVALID ARGUMENT
F9h	249	UNSUPPORTED PLATFORM
F8h	248	INSUFFICIENT BUFFER SIZE
F7h	247	MEMORY MAP ERROR
F6h	246	PCI PROGRAMMING ERROR

/sys/kernel/ryzen_smu_drv/smu_args

When written to, this file accepts 6x 32-bit words (a total of 192 bits) that specify the arguments used when executing an SMU command.

When read from, it lists either:

• The last values that were written to it before an SMU request was initiated
• The responses from the SMU after a request was completed

Note: All values sent to and read from this file must be in 6x 32-bit words encoded in little-endian order, arguments numbered from 1 to 6.

/sys/kernel/ryzen_smu_drv/smn

Allows reading and writing 32 bit values from the SMN address space. To perform an operation, write a value then read the file for the result.

The amount of bytes written indicates the operation performed:

Bits Written	Operation	Action Taken
32	Read	Reads 32 bit address and returns the result
64	Write	Writes the second 32-bit value to the address specified by the first 32 bits

Note: All values sent to and read from the device must are in little-endian binary format.

/sys/kernel/ryzen_smu_drv/pm_table_size

On supported platforms, this lists the maximum size of the /sys/kernel/ryzen_smu_drv/pm_table file, in bytes.

Note: File is a 64 bit word encoded in little-endian binary order.

/sys/kernel/ryzen_smu_drv/pm_table_version

On supported platforms, listed in the table below, this indicates the version of the metrics table.

Each version corresponds to a specific table size and layout that differs across processors.

The following table lists the known characteristics per version:

Hex	Platform	Table Size (Hex)
0x1E0004	Raven Ridge	0x6AC
0x1E0005	Raven Ridge	0x6AC
0x1E0101	Raven Ridge	0x6AC
0x240802	Matisse	0x7E0
0x240803	Matisse	0x7E4
0x240902	Matisse	0x514
0x240903	Matisse	0x518
0x2D0803	Vermeer	0x894
0x380804	Vermeer	0x8A4
0x380805	Vermeer	0x8F0
0x2D0903	Vermeer	0x594
0x380904	Vermeer	0x5A4
0x380905	Vermeer	0x5D0
0x370000	Renoir	0x794
0x370001	Renoir	0x884
0x370002	Renoir	0x88C
0x370004	Renoir	0x8AC
0x370005	Renoir	0x8C8
0x400005	Cezanne	0x944
0x2D0008	Milan	0x1AB0

Note: File is a 32 bit word encoded in little-endian binary order.

/sys/kernel/ryzen_smu_drv/pm_table

On supported platforms, this file contains the PM table for the processor, as updated by the SMU.

Note: This file is encoded directly by the SMU and contains an array of 32-bit floating point values whose structure is determined by the version of the table.

Module Parameters

The driver supports the following module parameter(s):

smu_timeout_attempts

When executing an SMU command, either by reading pm_table or manually, via smu_args and smu_cmd, the driver will retry this many times before considering the command to have timed out.

For example, on slower or busy systems, the SMU may be tied up resulting in commands taking longer to execute than normal. Allowed range is from 500 to 32768, defaulting to 8192.

Userspace Library

Included in this project is a userspace library, located at /lib to allow easy interaction with the driver. More details of the methods provided may be found in libsmu.h.

Example usage of the library is detailed below:

#include <stdlib.h>
#include <unistd.h>

#include <libsmu.h>

#define TEST_SMN_ADDR 0x50200

int main(int argc, char** argv) {
    smu_obj_t obj;
    unsigned int result;

    // Userspace library requires root permissions to access driver.
    if (getuid() != 0 && geteuid() != 0) {
        fprintf(stderr, "Program must be run as root.\n");
        exit(-1);
    }

    // Initialize the library for use with the program.
    if (smu_init(&obj) != SMU_Return_OK) {
        fprintf(stderr, "Error initializing userspace library.\n");
        exit(-2);
    }

    printf("Processor Codename: %s\n", smu_codename_to_str(&obj));
    printf("SMU FW: %s\n", smu_get_fw_version(&obj));

    if (smu_read_smn_addr(&obj, TEST_SMN_ADDR, &result) != SMU_Return_OK) {
        fprintf(stderr, "Error reading SMN address: 0x%08x\n", TEST_SMN_ADDR);
        exit(-3);
    }
    printf("SMN [0x%08x]: 0x%08x\n", TEST_SMN_ADDR, result);

    // Cleanup after library use has ended.
    smu_free(&obj);

    return 0;
}

N.B. This header file must be compatible with the version of the driver installed.

Example Usage

For Matisse & Vermeer processors, there are several commands that are known to work. See rsmu_commands.md for more information.

Commands may be executed either programatically using the library or under a shell by writing to the designated files.

Example usage via shell:

# Note: Does not persist across reboots

# Set the running PPT to 142 W (argument in milliwatts)
printf '%0*x' 48 142000 | fold -w 2 | tac | tr -d '\n' | xxd -r -p | sudo tee /sys/kernel/ryzen_smu_drv/smu_args && printf '\x53' | sudo tee /sys/kernel/ryzen_smu_drv/rsmu_cmd

# Set the running TDC to 90 A (argument in milliamps)
printf '%0*x' 48 90000 | fold -w 2 | tac | tr -d '\n' | xxd -r -p | sudo tee /sys/kernel/ryzen_smu_drv/smu_args && printf '\x54' | sudo tee /sys/kernel/ryzen_smu_drv/rsmu_cmd

# Set the running EDC to 140 A (argument in milliamps)
printf '%0*x' 48 140000 | fold -w 2 | tac | tr -d '\n' | xxd -r -p | sudo tee /sys/kernel/ryzen_smu_drv/smu_args && printf '\x55' | sudo tee /sys/kernel/ryzen_smu_drv/rsmu_cmd

# Set the PBO Scalar to 2x
# Calculation: 100 * scalar
printf '%0*x' 48 200 | fold -w 2 | tac | tr -d '\n' | xxd -r -p | sudo tee /sys/kernel/ryzen_smu_drv/smu_args && printf '\x58' | sudo tee /sys/kernel/ryzen_smu_drv/rsmu_cmd

As to the rest of the commands, we leave that as an exercise up to the user. :)