Chuwi Hi9 Air (Mediatek Helio X20 chipset)

Pretty complete hardware support and good stability with 8.1 (Oreo), 9.0 (Pie), 10 and 11 Treble GSIs.

CAVEAT: Please note that the standby battery drain is way higher for Pie and 11 GSIs (compared to Oreo) and Ten GSIs still seem to be stuck on boot.

Ten GSIs stuck-on-boot problem is solved by following these steps or installing this zip through TWRP recovery. For Magisk users, it's also necessary to use the phh-magisk instead of the official one to avoid problems with Zygote crashing. An expanded tutorial for installing Ten GSIs can be found here, and a working overlay for Ten GSI builds can be downloaded here.

Steps to install

Baseline: Hi9 Air with Chuwi 20181122 stock ROM. Restore Chuwi stock ROM via the MTK SP Flash Windows toolkit using the Format All + Download option, in case anything goes wrong.

• enable "OEM unlock" in Android developer options

  :information_source: type on build number seven times to unlock developer mode in Android system settings: System>About

• use factory settings reset in Android system settings

• wait for erase to finish and power off (long press)

• start device with power and vol+ simultaneously for bootloader menu, select "Fastboot Mode" via 'vol+', then confirm OK via 'vol-'

• unlock bootloader

  ℹ️ You may keep the bootloader locked if TWRP is installed via SP Flash as well and you subsequently install the system image and OpenGApps via TWRP...

  $ fastboot oem unlock
  

  Confirm OK on-screen via 'vol+'.

  :warning: When relocking the bootloader again via fastboot oem lock the device won't boot custom images any longer...

• flash image with the fastboot utility (after uncompressing the downloaded xz archive):

  $ fastboot erase system
  $ fastboot -u flash system system-arm64-aonly-vanilla-nosu.img
  $ fastboot reboot
  

  :repeat: This step may be repeated for later image releases with fixes and Android security patches (tested successfully for v31>32>123)...

  Alternatively, you could flash the img file via TWRP as "System Image". Refrain from formatting data, as the device will fail to boot then: -1: (Link) - unless you remove device encryption first: Using TWRP you have to install remove_encryption_97.zip and reboot to recovery before proceeding by reformatting the data partition in TWRP.

• wait patiently for another erase job to finish and initial boot (which now displays an "Android" animation instead of "CHUWI") to complete: This will take several minutes

Hardware support

Component	Comment
Camera	yes (both works, front cam orientation may be upside down)
Speaker / Mic	yes / yes
Bluetooth	yes (works for 8.1 GSI, with 9 GSI and above enable the Mediatek workaround under phh treble settings > misc features > Bluetooth workarounds )
WiFi	yes (but signal reception seems worse compared to stock ROM)
SIM / Mobile Data	partial (SIM1 only, does not always reactivate after standby - reboot required)
Voice	yes
SMS	yes
VoLTE	no (unresolved issue for MTK 6797)
Fingerprint	n/a
NFC	n/a
SD Card	yes
Casting	no, only via Google Home (as for Chuwi stock ROM)

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Tested by bofh2k - phh-treble 8.1 GSI v32 & 9 GSI v123 (arm64-aonly-vanilla-nosu) - 2020-02-29

Tested by santosst3 - phh-treble quack GSI v222 & roar GSI v300.l (arm64-aonly-vanilla) - 2021-02-08