Xiaomi Mi MIX 2S (polaris) Firmware Flash File Download [Stock ROM]
The Mi MIX 2S (codenamed polaris) was Xiaomi’s flagship smartphone featuring a ceramic body, Snapdragon 845 processor, and wireless charging. If your device is experiencing camera malfunctions, performance issues, wireless charging problems, or software instability, this guide provides the official MIUI fastboot ROMs and custom recovery needed for complete system restoration.
Important Notice: Verify your device codename is polaris before flashing. The Mi MIX 2S has premium features including ceramic construction and wireless charging that require specific firmware. Flashing incorrect firmware will result in a non-functional device.
Quick Device Specifications
- Device: Mi MIX 2S (polaris)
- Release Year: 2018
- Chipset: Qualcomm Snapdragon 845 (10nm)
- Display: 5.99″ IPS LCD, 1080 × 2160 pixels (18:9)
- Camera: 12MP + 12MP dual rear (2x optical zoom), 5MP front camera
- Battery: 3400 mAh with Qi wireless charging
- RAM: 6GB/8GB LPDDR4X
- Storage: 64GB/128GB/256GB UFS 2.1
- Security: Rear fingerprint scanner
- Special Feature: Ceramic body, wireless charging, bezel-less design
- Original OS: Android 8.0 Oreo, MIUI 9
Essential Downloads & Tools
| File / Tool | Download Link |
|---|---|
| Xiaomi Mi Flash Tool | Download Stable Version |
| Qualcomm USB Drivers | Download Latest Drivers |
| TWRP Recovery | TWRP 3.3.2B for polaris |
| ADB and Fastboot Tools | Official from Google |
| Mi Unlock Tool | Bootloader Unlock |
Official Fastboot ROM Collection
| Region / Variant | Build Version | Android | Release Date | Download Link |
|---|---|---|---|---|
| China Stable | V12.5.1.0.QDGCNXM | 10.0 | 2021-07-07 | Download |
| Global Stable | V12.0.3.0.QDGMIXM | 10.0 | 2020-12-28 | Download |
| Russia Stable | V12.0.2.0.QDGRUXM | 10.0 | 2020-12-15 | Download |
| Xiaomi.eu (Custom) | V12.5.1.0.QDGCNXM (Based) | 10.0 | — | Download |
| TWRP Recovery | 3.3.2B-0302 | 10.0 | — | Download |
Flashing Guide for Mi MIX 2S (polaris)
Method 1: Fastboot Flashing (Official)
- Driver Installation: Install Qualcomm USB drivers on your computer.
- Bootloader Unlock: Unlock bootloader using Mi Unlock Tool (requires waiting period).
- Enter Fastboot Mode: Power off device, then hold Volume Down + Power buttons.
- Flash Process:
- Extract the .tgz file to access firmware folder
- Open Mi Flash Tool and browse to extracted folder
- Select “Clean All” option for fresh installation
- Click “Flash” and wait for completion (5-7 minutes)
- First Boot: Initial boot may take 5-10 minutes as system optimizes.
- Wireless Charging Test: Test wireless charging functionality after setup.
Method 2: TWRP Recovery (Custom)
- Flash TWRP:
fastboot flash recovery twrp.img - Boot to TWRP: Hold Volume Up + Power during boot
- Backup Partitions: Backup persist and modem partitions first
- Install Custom ROM: Flash Xiaomi.eu zip from storage
- Wipe Data: Format data for clean installation
Frequently Asked Questions (FAQs)
Q1. Why is my wireless charging not working properly after update?
The Qi wireless charging requires specific firmware calibration. Flash the stock ROM and ensure you’re using an approved wireless charger. The ceramic back may also affect charging efficiency if not properly aligned.
Q2. Can I upgrade to Android 11 on Mi MIX 2S?
No, Android 10 was the final official Android version. However, there are custom ROMs like Pixel Experience and LineageOS 18.1 (Android 11) available through TWRP if you unlock the bootloader.
Q3. Why are my dual cameras not focusing properly?
The dual 12MP camera system with 2x optical zoom requires specific calibration. Flash the stock ROM and recalibrate through hardware test menu (##6484## → Camera Test).
Q4. Why is the China ROM version newer than the Global ROM?
Xiaomi typically provides longer update support for the Chinese market. The China variant received MIUI 12.5 with July 2021 security patches, while Global stopped at December 2020.
Device-Specific Troubleshooting
- Wireless Charging: The ceramic back may require specific alignment with wireless chargers. Use original Xiaomi wireless charger for best results.
- Camera Performance: The dual camera system with optical zoom needs proper calibration. Test both cameras and zoom functionality after flashing.
- Battery Optimization: The 3400mAh battery may need calibration after flashing. Use battery optimization features in MIUI.
- Performance Management: The Snapdragon 845 is still powerful. Use Game Turbo for enhanced gaming performance.
TWRP Installation Guide
- Unlock bootloader officially through Mi Unlock
- Boot to fastboot mode: Power off → Volume Down + Power
- Flash TWRP:
fastboot flash recovery twrp.img - Boot to TWRP:
fastboot boot twrp.img - Backup critical partitions: persist, modem, EFS
- Format Data: Wipe → Format Data → type “yes”
Note: Always backup your persist partition before flashing custom ROMs to avoid camera and sensor issues.
Version Comparison Advice
China ROM (V12.5.1.0): Newest features, latest security patches (July 2021), but may contain Chinese apps and lack some Google services optimization.
Global ROM (V12.0.3.0): Better Google services integration, stable for international users, with December 2020 security patches.
Russia ROM (V12.0.2.0): Similar to Global but optimized for Russian market with specific network bands.
Xiaomi.eu ROM: Best compromise – based on China ROM but debloated, with Google services added, and optimized for global use.
Special Considerations for Premium Device
Ceramic Body: The ceramic construction affects wireless charging and thermal management – ensure proper firmware support.
Wireless Charging: One of the first Xiaomi devices with Qi wireless charging – requires specific firmware optimization.
Bezel-less Design: The innovative design requires optimized software for accidental touch prevention.
Camera System: The dual 12MP cameras with 2x optical zoom provide excellent photography capabilities when properly calibrated.
