Recovery

Intro

The following documentation describes the process of recovering hardware from the brick state using an RTE and Dasharo open-source firmware.

External flashing

The external programming and recovery from bricks caused by Dasharo can be achieved by flashing only a portion of BIOS flash memory. Currently, due to various limitations of AMD firmware image assembling, Dasharo images do not incorporate the PSP firmwares and are only suitable to co-work with PSP firmware blobs present inside vendor images.

To flash the relevant portion of the BIOS to recover, the following flashrom layout layout_file is needed:

00000000:01cbffff reserved
01cc0000:01ffffff bios

The Dasharo image with Turin support occupies the last 0x340000 bytes of the BIOS flash, as this is the flash region being copied by PSP in the vendor image. We reuse it to copy the whole coreboot to RAM before jumping to reset vector.

RTECH341A

Prerequisites

Prepared RTE
6x female-female wire cables
pomona SOIC8 clip

Connections

To prepare the stand for flashing follow the steps described in the Generic test stand setup

Firmware flashing

To flash firmware follow the steps described below:

Login to RTE via ssh or minicom.
Turn on the platform by connecting the power supply.
Wait at least 5 seconds.
Turn off the platform by using the power button.
Wait at least 3 seconds.

Set the proper state of the SPI by using the following commands on RTE:

# set SPI Vcc to 3.3V
echo 1 > /sys/class/gpio/gpio405/value
# SPI Vcc on
echo 1 > /sys/class/gpio/gpio406/value
# SPI lines ON
echo 1 > /sys/class/gpio/gpio404/value

Starting with RTE distro v0.8.x the GPIOS are 517, 518, 516.

Wait at least 2 seconds.
Disconnect the power supply from the platform.
Wait at least 2 seconds.

Check if the flash chip is connected properly

flashrom -p linux_spi:dev=/dev/spidev1.0,spispeed=16000

Flash the platform by using the following command:
```
flashrom -p linux_spi:dev=/dev/spidev1.0,spispeed=16000 \
    -w [path_to_binary] --layout layout_file -i bios -N
```
The board sinks too much current which results in SPI Vcc to drop below an acceptable level when writing to flash. Reads are reliable, but write often fail. When PSU is off, the voltage on SPI chip is 2.5V-2.6V only from RTE. Sometimes it happens to go smoothly, but most of the time not. Using CH341A is more reliable, but leaves VCC always connected to the board, which tends to put the board in a limbo state. Recovering from such limbo requires disconnecting all power sources from the board (both PSU and CH341A). However, with OSFV cli the writes are somehow reliable, so it is recommended to use the utility.

Change back the state of the SPI by using the following commands:

echo 0 > /sys/class/gpio/gpio404/value
echo 0 > /sys/class/gpio/gpio405/value
echo 0 > /sys/class/gpio/gpio406/value

Starting with RTE distro v0.8.x the GPIOS are 516, 517, 518.

Turn on the platform by connecting the power supply.

The AMD board take longer to boot due to memory training happening on PSP side. Thus the first signs of life from open-source firmware may appear even after a couple of minutes (depends on amount of populated RAM).

Prerequisites

CH341a USB to SPI programmer
6x female-female wire cables
pomona SOIC8 clip

Connections

Connect pomona SOIC8 clip to the CH341a programmer.
Clip on the BIOS flash chip on the board.

Firmware flashing

To flash firmware follow the steps described below:

Disconnect the power supply from the platform.
Wait at least 2 seconds.
Check if the flash chip is connected properly
```
flashrom -p ch341a_spi
```

Flash the platform by using the following command:

flashrom -p ch341a_spi -w [path_to_binary] \
    --layout layout_file -i bios -N

Take off the pomona clip from the chip.
Turn on the platform by connecting the power supply.

The AMD board take longer to boot due to memory training happening on PSP side. Thus the first signs of life from open-source firmware may appear even after a couple of minutes (depends on amount of populated RAM).