Xiaomi Mi 9

Although this device is A-only, you have to choose GSI for A/B devices because this device is "system-as-root".

Tested images

AOSP 9.0 v119
AOSP Q v204

Hardware Support

Camera:

Basic usage works. Triple camera access works from modded GCAM Extented support works enabling it from Phh settings

Speaker / Microphone

Works

Bluetooth

A2DP AAC works
In-call broken

Wi-Fi

Works, tethering works

GPS

Works, including double band

NFC

Works

SIM / Mobile Data / Voice

Works, LTE+ works. Some GSI force 3G only, type *#*#4636#*#* and set LTE If that doesn't work use primary slot instead of secondary

VoLTE

Not tested

Dual-Sim

Working except: it's not possible to select main (4G) SIM it's not possible to set preference for 3g/4g in settings, use ##4636## instead second sim cannot use 4g due to the above issue

Fingerprint Reader

Works Broken on Always on Display (turn screen on first)

Brightness control

Works

Quick Charge

Works (9V/2A with USB PD charger)

Wireless Charge

Works

Type-c audio output

Works

Video recording:

Limited to 1080p/720p. Need to kang Pixel 3 media_profiles_V1_0.xml, /vendor/etc and overwrite the old one
media_profiles_V1_0.xml
Limited to 30fps. Need to copy media_profiles.xml to /vendor/etc
media_profiles.xml

Misc

Instagram video recording: Good and smooth (stock lags)

Tested By:

@phhusson - 17 March 2019
@koenkk - 05 April 2019
@linjie997 - 14 April 2019
@penn5 - 11 July 3187 & 2 October 9423 (descendant 3.0 & v119)
@Giton22 - 25 November 2019(AOSP v204 & LineageOS 17.0)

Flashing instructions

No need for magisk, nor no-verity, no-forceencrypt, etc... \

You simply need to flash vbmeta then system. \

Download vbmeta from https://github.com/TadiT7/xiaomi_cepheus_dump/raw/cepheus-user-9-PKQ1.181121.001-9.3.1-release-keys/firmware-update/vbmeta.img \

Download latest adb and fastboot drivers from https://developer.android.com

Connect the phone to your computer with the USB cable

Reboot to bootloader:

adb reboot bootloader

Flash vbmeta with

fastboot --disable-verity --disable-verification flash vbmeta vbmeta.img

Flash system with

fastboot flash system system.img

Reboot to recovery pressing power up + power

Factory reset, reboot

Applying a vendor OTA

This has been applied to update from vendor Pie to vendor Q, using miui_CEPHEUSEEAGlobal_V11.0.8.0.QFAEUXM_39255ef3ce_10.0.zip. This requires TWRP to install un-signed updates. Remove the zip's compatibility.zip, system.new.dat.br, system.patch.dat, system.transfer.list Edit META-INF/com/google/android/updater-script and remove: package_extract_file("firmware-update/vbmeta.img", "/dev/block/bootdevice/by-name/vbmeta"); and

ui_print("Patching system image unconditionally...");
block_image_update("/dev/block/bootdevice/by-name/system", package_extract_file("system.transfer.list"), "system.new.dat.br", "system.patch.dat") ||
  abort("E2001: Failed to update system image.");

Finally, flash the zip in twrp.