lk2nd

lk2nd is a custom bootloader for many different devices based on Qualcomm system-on-chips (SoCs), including smartphones, tablets, smartwatches and a few single board computers (SBCs). It simplifies booting standard operating systems by providing:

• A unified boot and flashing interface (Android Fastboot), independent of device-specific modifications made to the boot chain (e.g. the proprietary flashing interface on Samsung devices)
• Automatic device and hardware detection (e.g. display panels, batteries, ...)
• Additional bootloader features (e.g. file system boot, booting from SD card)
• Additional firmware features (e.g. booting secondary CPU cores if the firmware lacks PSCI support)
• Workarounds for various device-specific issues (e.g. USB on some Samsung devices, modem on Motorola smartphones, ...)
• Various debugging commands that allow better understanding of the hardware for research and development purposes

There are two different configurations:

• lk2nd: "secondary" bootloader intended for devices where existing firmware cannot be replaced easily (most smartphones and tablets). In this configuration, lk2nd does not replace the stock bootloader. Instead, it is packed into an Android boot image, which is then loaded by the stock bootloader just like the original Android image. The real operating system can be placed in the boot partition with 512 KiB offset or stored in a ext2 file system. It does not have to be Android or even Linux, any kind of kernel can be packed into an Android boot image.

• lk1st: primary bootloader intended for single-board computers (SBCs) and expert users. In this case, it is the "first" bootloader responsible for loading the main operating system.

This repository is a fork of the original open-source bootloader from Qualcomm (tag LA.BR.1.2.9.1-02310-8x16.0), which is a heavily modified version of the Little Kernel Embedded Operating System.

Supported SoCs

• lk2nd-msm8916: APQ8016, MSM8216, MSM8916, MSM8929, MSM8939
• lk2nd-msm8974: MSM8974
• lk2nd-msm8226: APQ8026, MSM8226, MSM8926

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

Supported devices

lk2nd-msm8916

• Alcatel OneTouch Idol 3 (4.7) - 6039*
• Alcatel OneTouch Idol 3 (5.5) - 6045*
• ARK Benefit A3 - peach
• Asus Zenfone 2 Laser (720p) - Z00L
• Asus Zenfone 2 Laser (1080p) - Z00T
• Asus Zenfone Max ZC550KL (2016) - Z010D
• BQ Aquaris M5 - piccolo (use lk2nd-msm8916-appended-dtb.img)
• BQ Aquaris X5 - paella, picmt
• DragonBoard 410c - apq8016-sbc
• HTC One M8s - m8qlul (quirky - see comment in dts/msm8916/msm8939-htc-m8qlul.dts)
• Huawei Ascend G7 - G7-L01
• Huawei Honor 5X - kiwi
• Huawei Y635 - Y635-L01 (quirky - see comment in dts/msm8916/msm8916-huawei-y635-l01.dts)
• Lenovo A6000
• Lenovo A6010
• Lenovo PHAB Plus - PB1-770M, PB1-770N, PB1-770P
• LG K10 (m216) - K420
• LG Leon LTE (c50) - H340, H342, H343, H345, MS345, etc
• LYF Wind 1 - ls5010
• Marshall London
• Motorola Moto E (2015) - surnia
• Motorola Moto G (2015) - osprey
• Motorola Moto G4 Play - harpia
• Samsung Galaxy A3 (2015) - SM-A300F, SM-A300FU
• Samsung Galaxy A5 (2015) - SM-A500F, SM-A500FU, SM-A500YZ, SM-A500H
• Samsung Galaxy A7 (2015) - SM-A700YD
• Samsung Galaxy Ace 4 - SM-G357FZ (quirky - see comment in dts/msm8916/msm8916-samsung-r02.dts)
• Samsung Galaxy Core Max - SM-G5108Q (quirky - see comment in dts/msm8916/msm8916-samsung-r08.dts)
• Samsung Galaxy Core Prime LTE - SM-G360F
• Samsung Galaxy E7 - SM-E7000
• Samsung Galaxy Grand Prime - SM-G530FZ, SM-G530W, SM-G530Y (G530Y is quirky - see comment in dts/msm8916/msm8916-samsung-r11.dts)
• Samsung Galaxy J3 (2016) - SM-J3109, SM-J320YZ
• Samsung Galaxy J3 Pro - SM-J3110, SM-J3119
• Samsung Galaxy J5 (2015) - SM-J5008, SM-J500F, SM-J500FN, SM-J500H, SM-J500M
• Samsung Galaxy J5 (2016) - SM-J5108, SM-J510F, SM-J510FN, SM-J510UN
• 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 (2015) - SM-T355, SM-T355Y, SM-T357W
• Samsung Galaxy Tab A 9.7 (2015) - SM-T550, SM-T555
• Samsung Galaxy Tab E 9.6 WiFi (2015) - SM-T560NU
• Vodafone Smart prime 6
• Wileyfox Swift - crackling
• Xiaomi Mi 4i - ferrari
• Xiaomi Redmi 2 - wt86047, wt88047
• Yamada EveryPad III (rebrand of Lenovo PHAB Plus)

lk2nd-msm8974

• Fairphone 2 - FP2
• LG G3 - D855
• LG Google Nexus 5 - hammerhead D820, D821
• Samsung Galaxy S5 - SM-G900F

lk2nd-msm8226

• ASUS ZenWatch 2 - sparrow
• Huawei Watch - sturgeon
• LG G Watch R - lenok
• Samsung Galaxy Grand 2 - SM-G7102

Installation

1. Download lk2nd.img (available in Releases)
2. Flash lk2nd.img using the stock flashing interface:
   • Fastboot: fastboot flash boot lk2nd.img
   • Samsung: heimdall flash --BOOT lk2nd.img

If you get fastboot: error: Couldn't parse partition size '0x' try one of the following workarounds:

• fastboot flash:raw boot lk2nd.img
• fastboot boot lk2nd.img, then fastboot flash lk2nd 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 directly from its fastboot interface.

Note: fastboot flash boot boot.img will flash the actual boot image with 512 KiB 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.

Troubleshooting

If the device shows up via fastboot you can get a log file from lk2nd using fastboot oem lk_log && fastboot get_staged <output-file>, where <output-file> is either some text file to write to (e.g. output.txt) or /dev/stdout to write the log to standard output.

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- lk2nd-msmXXXX

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-lk2nd-msmXXXX/lk2nd.img.

Note: Unlike lk2nd, lk1st is still experimental and therefore not described here yet.

Porting

To other devices with a supported SoC

• 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/lk2nd-<target>.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

Ask on #postmarketos-mainline (Matrix or IRC).