OpenBMC

• 1: ASRock Rack
• 1.1: ASRock Rack X570D4U
• 1.1.1: ASRock Rack X570D4U mainboard: pinout
• 1.1.2: ASRock Rack X570D4U mainboard: I2C busses
• 1.1.3: ASRock Rack X570D4U mainboard: GPIO
• 1.1.4: Programming SPI flash with an FT2232 breakout board
• 1.1.5: ASRock Rack X570D4U mainboard: temperature sensors
• 1.1.6: ASRock Rack X570D4U mainboard: fans
• 1.2: ASRock Rack PAUL
• 1.2.1: ASRock Rack PAUL: GPIO

1 - ASRock Rack

ASRock Rack is a hardware manufacturer which has produced multiple mainboards and devices which should be capable of running OpenBMC. More information on the boards Nicolai Electronics is working can be found on the board specific pages.

1.1 - ASRock Rack X570D4U

Project status: in progress

The ASRock Rack X570D4U series of mainboards consists of three mainboards with an AMD X570 chipset and AM4 socket. ASRock Rack sells the board in three versions: a cost reduced version without a 10Gbit NIC (X570D4U), a version with an Intel 10Gbit NIC (X570D4U-2L2T) and a version with a Broadcom 10Gbit NIC (X570D4U-2L2T/BCM). These boards contain an Aspeed AST2500 BMC chip. A Baseboard Management Controller (BMC) is a small computer built into the motherboard that allows for out-of-band management. It allows for remote power control, KVM (remote keyboard, video and mouse) control, virtual media insertion and much more.

These parts make for quite a powerful system, unfortunately the operating system shipped by ASRock Rack is proprietary and dos not allow for easy modification. To allow for a more secure, transparent and customizable experience we are working on adding support for this mainboard to the mainline Linux kernel and the OpenBMC Linux distribution for BMCs.

Official documentation is provided in ASRock Racks manual for these mainboards. Not a all headers and connectors are described in this manual. The pinout of the undocumented connectors and headers can be found on the pinout page.
The BMC has a programming header, a debug serial port, I2C busses and GPIOs.

Project status

Enabling the use of the mainline Linux kernel and OpenBMC on this hardware is an ongoing effort. An initial port of OpenBMC missing most board specific features can be found here.

1.1.1 - ASRock Rack X570D4U mainboard: pinout

This page describes the undocumented headers and connectors on the ASRock X570D4U mainboard. The official manual for this mainboard describes most other connectors and headers.

BMC debug header

This header labeled BMC_DEBUG1 provides access to the debug serial port of the AST2500 SoC (UART 5). The UART works with 3.3v level signals and provides a 3.3v output and can be found on the bottom left of the mainboard.

Using this port you can access the U-Boot command prompt, the Linux bootlog and a shell.

BMC programming header

This header labeled BMC_PH1 provides access to the MX25L51245G 64MB flash chip containing the BMC firmware. Using an exernal SPI flash programmer this port allows for unbricking and easy reflashing of the BMC firmware during development.

This interface uses 3.3v level signals. Connecting the BMC RESET# pin to GND disables the AST2500, allowing an exernal programmer to reprogram the flash chip without interference from the SoC.

Manufacturing mode header

This header labeled MFG1 is connected to GPIO H4 of the AST2500 SoC. With the official firmware installed shorting this jumper makes the BMC boot into a special debug mode, dropping to a root shell on the BMC_DEBUG1 port. When running OpenBMC this GPIO is available for custom applications.

Chassis identification

These three headers labeled CHASSIS_ID1, CHASSIS_ID2 and CHASSIS_ID3 are connected to GPIO G1, G2 and G3 of the AST2500 SoC for ID1, ID2 and ID3 respectively. On production boards these headers appear to not have been installed, but they are functional. When running OpenBMC these GPIOs are available for custom applications.

1.1.2 - ASRock Rack X570D4U mainboard: I2C busses

This page describes the I2C busses and connected on-board devices on the ASRock X570D4U mainboard.

I2C bus 0

This bus is connected to the AUX_PANEL1 connector. SMBus alert for this bus is connected to GPIO 52 (G4) named input-aux-smb-alert-n.

I2C bus 1

This bus is used for controlling on-board devices that are used when the host is on.

PCA9557 IO expander

Nuvoton NCT6796D-R SuperIO

This chip can read the CPU and chipset temperatures. It should be possible to use the newly added nct6775-i2c driver to use this device.

Using the NCT6775-I2C driver

The OpenBMC port for the X570D4U already includes the nct6775-i2c driver in it’s kernel, but as the SuperIO device only appears on the bus when the host system is powered on the driver needs to be loaded in and unloaded based on power state changes. This has not been implemented yet.

The driver can be manually loaded in using the following command:

echo "nct6775 0x2d" > /sys/bus/i2c/devices/i2c-1/new_device

If the driver was loaded correctly then you should now be able to find a folder called hwmon in the device folder /sys/bus/i2c/devices/i2c-1/1-002d. This folder will contain a symlink to the hwmon interface for the SuperIO chip. If the folder is missing then your kernel does not include the nct6775-i2c driver.

Directly accessing and reading the temperature registers

Alternatively the temperatures can be read using this shell script, for which no kernel driver is required:

#!/bin/bash
i2cset -y 1 0x2d 0x4e 0x04
while :
do
    TSI0INT=$((16#$(i2cget -y 1 0x2d 0x09 | cut -f2 -dx)))
    TSI0FRC=$(($((16#$(i2cget -y 1 0x2d 0x0a | cut -f2 -dx)))>>5))
    TSI1INT=$((16#$(i2cget -y 1 0x2d 0x0b | cut -f2 -dx)))
    TSI1FRC=$(($((16#$(i2cget -y 1 0x2d 0x0c | cut -f2 -dx)))>>5))
    echo "TSI0_TEMP: $TSI0INT.$TSI0FRC °C / TSI1_TEMP: $TSI1INT.$TSI1FRC °C"
    sleep 0.5
done

Nuvoton W83773G

This device is available on the versions of the X570D4U which include a 10Gbit network adapter. It monitors the temperature of the 10Gbit NIC.

cat /sys/class/hwmon/hwmon0/temp2_input

I2C bus 2

This bus is used for connecting to exernal power supplies with SMBus monitoring support using the PSU_SMB1 connector. SMBus alert for this bus is connected to GPIO 54 (G6) named input-psu-smb-alert-n.

I2C bus 3

This bus has an unknown purpose.

I2C bus 4

This bus is used to connect to expansion cards inserted into the PCI-Express slots of the mainboard.

NXP PCA9545A I2C bus switch

I2C bus 5

This bus is connected to the BMC_SMB_1 connector. The BMC_PRESENT_1_N signal on the BMC_SMB_1 connector is connected to GPIO 132 (Q4) named input-bmc-smb-present-n.

I2C bus 7

This bus is used for connecting to the FRU EEPROM and the RAM DIMMs.

I2C bus 8

This bus is connected to the IPMB_1 connector.

1.1.3 - ASRock Rack X570D4U mainboard: GPIO

This page describes the GPIOs of the ASPEED AST2500 BMC on the ASRock X570D4U mainboard.

1.1.4 - Programming SPI flash with an FT2232 breakout board

Connection diagram

1.1.5 - ASRock Rack X570D4U mainboard: temperature sensors

This page describes the temperature sensors on the X570D4U.

Nuvoton NCT6796D-R SuperIO

This device can be accessed via I2C bus 1 at address 0x2D.

Nuvoton W83773G

This device can be accessed via I2C bus 1 at address 0x4C.

1.1.6 - ASRock Rack X570D4U mainboard: fans

This page describes the fan connectors on the X570D4U.

Fan connectors

Fan 1-3 connector pinout

Fan 4-6 connector pinout

1.2 - ASRock Rack PAUL

Project status: in progress

The ASRock Rack PAUL is a PCI-express add-in card for servers and workstations containing an Aspeed AST2500 BMC chip. A Baseboard Management Controller (BMC) is a small computer that allows for out-of-band management. It allows for remote power control, KVM (remote keyboard, video and mouse) control, virtual media insertion and much more.

These parts make for quite a powerful system, unfortunately the operating system shipped by ASRock Rack is proprietary and dos not allow for easy modification. To allow for a more secure, transparent and customizable experience we are working on adding support for this mainboard to the mainline Linux kernel and the OpenBMC Linux distribution for BMCs.

Official documentation is provided in ASRock Racks manual.

1.2.1 - ASRock Rack PAUL: GPIO

This page describes the GPIOs of the ASPEED AST2500 BMC on the ASRock Rack Paul card.