Unlocking Bootloader - Lenovo Sisley S90-a

Disclaimer :This guide for educational purpose only, We not responsible if your device bricked after following this tutorial. 

What is a Bootloader?
The simpliest explaination is when you turn on your operating system you will notice that the phone will vibrate before it boot the Operating System or the Recovery mode. Bootloader is a code that is executed before any Operating System starts to run.



Why Unlock Bootloader?
If you want root, you’d be wanting to flash Custom ROM post-root, and if you want to install a Custom ROM, you’d need to have your stock bootloader unlocked. In simple terms Unlocking the bootloader allows you to install custom Firmware on your Android phone.

Warning: Unlocking your phone’s bootloader voids its warranty. It also completely wipes (formats) your Android phone’s internal memory including applications, contacts, SMS and MMS messages etc.

How to unlock Bootloader?
Requirements :

• PC with windows 7 preferably 32 bit,  windows 8 and windows 10 not suitable for the guide. 
• A good shape USB cable
• We need to install all necessary driver and a flasher program, download below files and begin install it one by one

Extract all downloaded files:

Qualcomm Windows Driver
Lenovo USB Driver
QPST 2.7.422

Open extracted file go to TestCertificate > rightclick "qcusbtest" and Install Certificate
follow installation wizard and restart the computer.

Prepare device to ready for the next step.

Turn on USB debugging, go to System > About Phone > Device Information >
Tap 5 times "Build Number"
The press "back" then open Developer Options > check USB DEBUGGING

• Put the phone on diagnosis mode

Kitkat (4.4.4.2) - connect the phone to pc using USB cable then make dial *#*#8899#*#*,
then just select OK

Lollipop (5.0.2) - Turn off your phone, then press volume + down & power, release after the logo prompt.

Look on the device manager on your pc, you should see the following drivers:
1. Lenovo Composite ADB Interface
2. Modem > Lenovo HS-USB Modem Phone #2
3. COM Port & LPT > Lenovo HS-USB Diagnostic (COM8)
Lenovo HS-USB NMEA (COM9)

COM port number doesn't matter. it change depends on the pc model or laptop.

Downloads :

• S90-ROW_UnLock_BootLoader - Lenovo s90-a Kitkat firmware
• S90-CN_UnLock_BootLoader - Lenovo s90-u & s90-t with Android KitKat firmware
• S90-ROW_UnLock_BootLoader_L - Lenovo s90-a Lollipop firmware
• S90-CN_UnLock_BootLoader_L -Lenovo s90-u & s90-t with Android Lollipop firmware

Unlocking bootloader for Lenovo S90 running Android KitKat or Android Lollipop (ROW/CN) 

1. Download the suitable files for your devices, and extract it contents on any drive. example C:\S90-ROW_UnLock_BootLoader
2. Run QFIL flasher program from Start > All Programs > QPST > QFIL 
3. On the Programmer Path, select prog_emmc_firehose_8916.mbn from the extracted folder, it will automatically load  Search Path
4. Click on Load XML.... button and select rawprogram0.xml and patch0.xml also from extracted folde
5. Click the Download button and wait the process until it finish, device will automatically reboot.

Done, now you have successful unlocking your Lenovo S90 Sisley, continued with rooting and install custom recovery for your Lenovo S90 Sisley.

Credits:
- Andy Suwito (Androidrookies Admin)
- S90 Admins
- Felix Alfaro Godito 
- Sevenmaxx of Russian Lenovo forum