lk2nd

lk2nd is a bootloader for Qualcomm MSM devices (at the moment only MSM8916 and MSM8939), based on the CodeAurora Little Kernel fork. It provides an Android Fastboot interface on devices where the stock bootloader does not provide Fastboot (e.g. Samsung).

On MSM8916 it is also used for some quirks for mainline devices, e.g. to set a proper WiFi/BT MAC address in the device tree.

lk2nd does not replace the stock bootloader. It is packaged into an Android boot image and then loaded by the stock bootloader as a "secondary" bootloader. The real Android boot image is placed into the boot partition with 1 MB offset, and then loaded by lk2nd.

Supported SoCs

• msm8916-secondary: MSM8216, MSM8916, MSM8929, MSM8939
• msm8974-secondary: MSM8974
• msm8226-secondary: MSM8226, MSM8926

See Chipsets page on the EFIDroid wiki for an exact mapping of LK targets to SoCs.

Supported devices

• Alcatel OneTouch Idol 3 (5.5) - 6045*
• Asus Zenfone 2 Laser (720p) - Z00L
• Asus Zenfone 2 Laser (1080p) - Z00T
• BQ Aquaris X5 (paella, picmt)
• Lenovo PHAB Plus - PB1-770M, PB1-770N
• LG K10 (m216) - K420 (see notes in dts/msm8916-lg.dts for now)
• Marshall London
• Motorola Moto E (2015, surnia)
• Motorola Moto G4 Play (harpia)
• Samsung Galaxy A3 (2015) - SM-A300FU
• Samsung Galaxy A5 (2015) - SM-A500F, SM-A500FU
• Samsung Galaxy Grand Prime - SM-G530W
• Samsung Galaxy J3 (2016) - SM-J3109
• Samsung Galaxy J3 Pro - SM-J3110, SM-J3119
• Samsung Galaxy J5 (2015) - SM-J5008, SM-J500F, SM-J500FN, SM-J500H
• Samsung Galaxy J5 (2016) - SM-J5108, SM-J510F, SM-J510FN
• Samsung Galaxy J7 (2015) - SM-J7008, SM-J700P
• Samsung Galaxy On7 (2015) - SM-G6000
• Samsung Galaxy S4 Mini Value Edition - GT-I9195I
• Samsung Galaxy Tab 4 10.1 (2015) - SM-T533
• Samsung Galaxy Tab A 8.0 LTE (2015) - SM-T357W
• Samsung Galaxy Tab A 9.7 WiFi (2015) - SM-T550
• Vodafone Smart prime 6
• Wileyfox Swift
• Xiaomi Mi 4i
• Xiaomi Redmi 2 (wt86047, wt88047)

Installation

1. Download lk2nd.img (available in Releases)
2. Flash lk2nd.img using the stock flashing procedure:

• Fastboot: fastboot flash boot lk2nd.img
• Samsung: heimdall flash --BOOT lk2nd.img

Usage

lk2nd provides the standard Android fastboot protocol for flashing/booting Android boot images.

Press Volume Down while booting to enter Fastboot mode. Press Volume Up while booting to boot into Recovery mode.

Note: If your stock bootloader uses the same key combinations, you need to wait a bit before pressing the volume keys. Usually, waiting until the screen turns on and/or the device vibrates should be enough to make the stock bootloader ignore the keys.

fastboot flash lk2nd lk2nd.img can be used to update lk2nd directory from its fastboot interface.

Note: fastboot flash boot boot.img will flash the actual boot image with 1 MB offset into the boot partition. This is done to avoid replacing lk2nd (since it is also booted from the boot partition).

Other fastboot commands work normally.

Building

Check Supported SoCs for the make target you should use below. (It depends on the SoC of your device.)

$ make TOOLCHAIN_PREFIX=arm-none-eabi- msmXXXX-secondary

Requirements:

• ARM (32 bit) GCC tool chain
  • Arch Linux: arm-none-eabi-gcc
• Device Tree Compiler
  • Arch Linux: dtc

Replace TOOLCHAIN_PREFIX with the path to your tool chain. lk2nd.img is built and placed into build-msm8916-secondary/lk2nd.img.

Porting

To other MSM8916 devices

• Add a simple device tree to dts/. You just need model and the qcom,msm-id/qcom,board-id from downstream.

To other SoCs

Qualcomm maintains separate branches for various groups of SoCs. The branches can be seen on the Chipsets page on the EFIDroid wiki. This version of lk2nd is based on the LA.BR branch for MSM8916. There is a fork for MSM8953 based on the LA.UM branch.

The bootloader will work best when you use the correct branch for your device. Older platforms are usually kept around by Qualcomm but barely tested and may not work, or not even compile.

However, if make files for your SoC are present in this version or the MSM8953 fork you can try to enable it and see if it works well enough for you. Otherwise you would need to go through the Git history and pick the relevant commits to another branch from https://source.codeaurora.org/quic/la/kernel/lk/.

To enable support for a SoC that is already present in this repository:

1. Create a new project/<target>-secondary.mk which looks like the others.
2. Try to compile it and fix all the compile errors.
3. Try to run it and hope that it works.

Good luck!

Contact

Ping minecrell/Mis012 on #postmarketos-mainline.