Xiaomi Redmi 4X (xiaomi-santoni)

Features
Flashing	Works
USB Networking	Works
Internal storage
SD card
Battery	Works
Screen	Works
Touchscreen	Works
Multimedia
3D Acceleration
Audio	Works
Camera	Broken
Camera Flash
Connectivity
WiFi	Works
Bluetooth	Partial
GPS
NFC
Modem
Calls
SMS
Mobile data
Miscellaneous
FDE	Partial
USB OTG	Works
HDMI/DP
Sensors
Accelerometer
Magnetometer
Ambient Light
Proximity
Hall Effect
Haptics
Barometer

Xiaomi Redmi 4x
	; xiaomi-santoni running pmOS demos
Manufacturer	Xiaomi
Name	Redmi 4x
Codename	xiaomi-santoni
Released	2017
Type	handset
Hardware
Chipset	Qualcomm Snapdragon 435 (MSM8940)
CPU	Octa-core 1.4 GHz Cortex-A53
GPU	Adreno 505
Display	720x1280
Storage	16 GB / 32 GB / 64GB
Memory	2 GB / 3 GB / 4 GB
Architecture	aarch64
Software
Original software	Android (MIUI)
Original version	6.0
Extended version	7.1
postmarketOS
Category	testing
Pre-built images	no
Mainline	yes
postmarketOS kernel	3.18.140
Unixbench Whet/Dhry score	1526.7

Contributors

pinoaffe
asriel-danctnix
Danct12

Maintainer(s)

Danct12

Users owning this device

Alula
Asriel
Bczeman
Cewbdex (Notes: + land device owned)
Danct12
Dreadlh (Notes: 2/16 GB Second phone)
Kisekinopureya (Notes: My test subject)
Pinoaffe
Shipa (Notes: partially Ubuntu Touch maintainer)
Tau (Notes: CrDroid. Fingerprint reader broken)
TheBads
UxAmadeus (Notes: Broken touchscreen)

Mainline kernel?

There's ongoing effort to bring up mainline kernel on MSM8937 platform, with initial focus on santoni: [1].

MSM8937/40 is pretty close to MSM8916, so a lot of drivers can be re-used with proper device tree and minimal address remapping in some places.

Parts	Components	In Torvalds tree?
Chipset	MSM8940	No
GPU	Adreno 505	Yes (a5xx_gpu.c)
Touch Screen	FT5X06	Yes (edt-ft5x06.c)
Fingerprint Sensor	FPC1020/Goodix	No
Accelerometer + Gyroscope	ICM20607/BMI120	No/Yes (bmi160_i2c.c)
ALSPS	STK3X1X	Yes (stk3310.c)
Magnetometer	YAS537	Yes (yamaha-yas530.c)
Sound	AW87319	No
Notifications LED	AW2013	Yes (leds-aw2013.c)
Front Camera	OV5675	Yes (ov5675.c)
Back Camera	S5K3L8	No

More information on this port

The upstream msm-3.18 kernel is a fork of https://github.com/bitrvmpd/msm-3.18
Most of this work was done for my project (Arch Linux on Redmi 4X), and the progress are backported to postmarketOS in order to help development.

Bootloader Unlocking

Like other Xiaomi devices, the user will have to acquire the bootloader unlock key: https://en.miui.com/unlock

The device will not unlock if the device isn't 7 days old (from the time when your device connects to internet and powered on)

If unlock fails at "Can't get info", start unlock process, disconnect USB and reconnect it once the counter hits 99%.

Key combinations for entering Recovery/Fastboot

Recovery

Turn the device off (or restart also works)
Hold both volume buttons (+ and -) and power button
Keep holding until you got to recovery.

Fastboot

Same as recovery, but this time hold the volume down key instead of both keys.

Installation

Installation over fastboot works, Android recovery zip installation is untested.

Bluetooth

Bluetooth on this phone is using the WCNSS chip, which provides two SMD channels to the BT core, one for command and one for event packets. Support for Bluetooth HCI SMD can be added using this patch.

With that patch applied, the Bluetooth interface can be bring up by set /sys/module/hci_smd/parameters/hcismd_set to 1. Then install bluez, start the service and use bluetoothctl to control it.

As right now, it seems to connect, but disconnect very quickly, it doesn't ask for pair code when connecting, so this needs to be investigated.

Serial Connection (UART)

The Serial Connection of the santoni has been tested only on reception mode, with 3.3v TTL to USB FT232RL. This example is an output when starting to fastboot.

Warning: the test point is very small, try to solder only if you're an expert on soldering or you may break the motherboard wirings.

Wiring: (Santoni TX --> FT232RL RX) and (Santoni GND --> FT232RL GND)