The wiki is being retired!

Documentation is now handled by the same processes we use for code: Add something to the Documentation/ directory in the coreboot repo, and it will be rendered to https://doc.coreboot.org/. Contributions welcome!

Status

Thanks for your interest in Lenovo T420 port. The code has not been merged yet, you can see the code on gerrit.

ATTENTION: You must cherry-pick this patch before building. (It's merged to upstream, you can cherry-picked the T420 port on the upstream coreboot code.)

Issues:

The USB beside express card cannot funtion after S3 resume if CONFIG_USBDEBUG is set (work around: reload ehci-pci module)
Badly seated RAM may prevent booting (not really a problem but coreboot is more suspicious to this than vendor BIOS)
Boot failure with quad core Ivy Bridge processor with 8G DDR3L module (Bug #6, work around:revert 9f1fbb9a3002e8d74d53d7973bd1c7e3d4879238)

Tested:

Ivy Bridge processor (see below)
RAM module combinations of 2G+0, 4G+0, 8G+0, 0+8G, 4G+8G, 8G+8G
S3 (Suspend to RAM)
msata
USB
Video (internal)
Sound (integrated speakers, integrated mic, external headphones, external mic)
LAN
mini-PCIe slots (wlan)
bluetooth
Linux (through GRUB-as-payload)
Windows (through SeaBIOS as payload or chainload SeaBIOS from GRUB payload, using a VGA BIOS)
DVD-ROM drive
SD card slot
trackpoint
touchpad
webcam
Fn hotkeys (backlight control, suspend, thinklight)
Thinklight
dock (tested with a TYPE 4337)

Not Tested:

Video (VGA and Displayport)
Expresscard slot (including hotplugging)
mini pci-e wwan
Fingerprint reader.
Thermal management

proprietary components status

CPU Microcode (optional): you may need it if your system is unstable (especially you're using a ES/QS processor)
VGA option rom (optional): you need it if you want graphics in SeaBIOS but most payloads should work without it (text mode or corebootfb mode)
ME(Management Engine) => you do not have to touch it(just leave it where it is)
EC(Embedded Controller) => you do not have to touch it(just leave it where it is)

Building

A build instruction has been written on bitbucket.

Flashing

T420 has an SOIC-8 flash chip of 8M. It's subdivided in roughly in 3 parts:

Descriptor (12K)
ME firmware (5M-12K)
System flash (3M)

ME firmware is not readable. Vendor firmware locks the flash and so you need to flash externally (unless until someone figures out a way around it).

Proceeds as follows:

Turn off your laptop, remove battery and AC adapter.
Disassemble the T420 laptop as the hardware maintenance manual says. You have to take out the mainboard, because the flash chip is under the magnesium stucture frame.
Connect your external SPI flasher to the SPI chip and flash it. Using an SOIC-8 clip is recommended.

When the laptop is running coreboot, you can reflash the firmware using flashrom:

 flashrom -p internal:laptop=force_I_want_a_brick -w <coreboot image>

Ivy Bridge processor support

Sandy Bridge and Ivy Bridge processor use the same socket, so an Ivy Bridge processor can be installed. To use native graphics init, you should use a patch on gerrit so that coreboot can use the correct code for native graphics init. You can also use a VGA option ROM with SeaBIOS, adding VGA option ROMs for both type of graphics manually is recommended (See the build instructionn above).

Up to now, an i5-3340M and an i7-3720QM(QS version) is tested.

Board:lenovo/t420