IPMI Block Transfer (BT) driver

The driver can be found in src/drivers/ipmi/ (same as KCS). It works with BMC that provides a BT I/O interface as specified in the IPMI standard. See “Intelligent Platform Management Interface Specification”, v2.0, Rev. 1.1 for more details on the interface and IPMI in general.

The driver detects the IPMI version and reserves the I/O space in coreboot’s resource allocator.

For developers

To use the driver, select the IPMI_BT Kconfig and add the following PNP device (in example for the BT at 0xe4):

chip drivers/ipmi
    device pnp e4.0 on end        # IPMI BT
end

Note: The I/O base address must be aligned to 4.

The following settings can be set in a device tree:

Setting

Type/Default

Description/Purpose

wait_for_bmc
Boolean
false

Wait for BMC to boot. This can be used if the BMC takes a long time to boot after PoR.

bmc_boot_timeout
Integer
0

The timeout in seconds to wait for the IPMI service to be loaded. Will be used if wait_for_bmc is true.

Debugging/testing the driver

ipmi_sim from OpenIPMI project can be used by running ipmi_sim -d in one console to watch what’s being sent/received and starting QEMU like this in another console:

qemu-system-x86_64 \
    -M q35,smm=on \
    -bios build/coreboot.rom \
    -chardev socket,id=ipmichr0,host=localhost,port=9002,reconnect=10 \
    -device ipmi-bmc-extern,chardev=ipmichr0,id=bmc0 \
    -device isa-ipmi-bt,bmc=bmc0,irq=0 \
    -serial stdio

A simpler alternative is to use QEMU’s builtin BMC simulator:

qemu-system-x86_64 \
    -M q35,smm=on \
    -bios build/coreboot.rom \
    -device ipmi-bmc-sim,id=bmc0 \
    -device isa-ipmi-bt,bmc=bmc0,irq=0 \
    -serial stdio

References

Useful links on the subject: