WC1

Galaxy Gear S2 Classic

The Gear S2 classic is a Tizen-based smartwatch released in 2015. See gsmarena for detailed specs. The codename used in Tizen and Recovery seems to be "WC1".

As the vendor kernel is very old (3.4) and there's no existing abstraction for the Tizen HAL, a mainline Linux port for this watch is being attempted instead.

Downstream sources available at https://github.com/casept/samsung-wc1-sources, as Samsung no longer hosts them.

Hardware docs

Recovery mode and flashing

Like other Samsung watches, the Gear S2 classic can either be flashed wirelessly via the NetOdin protocol, or using the regular Odin protocol by opening it up and soldering a USB cable to some internal pads. See e.g. this XDA thread for the pinout.

Note that flashing the BOOT partition with a bad kernel will result in a broken recovery and inability to use wireless download mode, so make sure you have USB connected before working on the watch.

List of peripherals and their kernel driver state

Most of the hardware in this watch seems to have drivers in the mainline kernel, especially the SoC and most of the regulators.

Samsung Gear S2 Classic

Chip	Function	Driver state in mainline Linux	Notes
Exynos 3250	SoC	Supported	DTS for dev boards based on it exist
WM1831	Microphone DAC	Supported
BCM4343W	WLAN and BT	Unsupported	Infineon still maintains this chip. There's a patch for recent kernels (5.15) available on Infineon's support site. A quite complete datasheet exists here.
SENN5DDPS2	NFC	Possibly supported	There exists a kernel driver for 5th generation Samsung NFC chips, whether this chip is part of it is unknown.
BCM53950	Wireless charge controller	Unsupported	No public datasheet, Samsung code seems readable enough and quite short (~1500LoC)
ISA1000A	vibrator motor controller	Unsupported	No datasheet, but probably only requires SoC PWM+GPIO, Samsung driver ca. 500LoC (drivers/motor/isa1000a_vibrator.c)
Unknown IC	hall effect sensor, crown	Unsupported	Connected via I2C, Samsung driver at drivers/input/misc/sec_rotary.c, ~1300LoC
CYTMA525	touchscreen controller	Supported
MAX77836	MUIC	Supported	downstream kernel judges jig modes based on resistor connected to this via USB
ATSAMG55G19A	sensor hub	unknown	possibly supported via "Samsung sensor hub" driver. Sensor chips are connected to this and not the SoC directly.
Unknown (marked "OCTA")	LCD controller	unknown	unknown

Debugging and Jigs

The device exposes a UART via the USB pads if ID is connected to GND with a 619k resistor. D+ goes to TX on the TTL adapter and D- goes to RX. VCC does not need to be connected. This works identically to other Samsung smartphones.

Connecting to the device via UART yields the following output on startup:

= 0x00
PMIC_STATUS1    = 0x27
PMIC_STATUS2    = 0x11
PMIC_OFFSRC     = 0x00
PMIC_PWRON      = 0x08
PMIC_IRQ1       = 0xc3
PMIC_IRQ2       = 0x11
PMIC_IRQ3       = 0x00
PMIC_RTC_OFFSRC = 0x00
PMIC_RTC_SMPL   = 0x23
pwm-0: stop, tcon = 0x510000
pwm-0: prescaler = 1, divider = 3
pwm-0: src clk = 50000000, prescaler = 1, div = 8
pwm-0: freq = 3125000, request freq = 25344
pwm-0: tcnt = 0x7b, tcmp = 0x79
s5p_check_reboot_mode: INFORM3 = 0 ... skip
board_ps_hold_control: state (1)
s5p_reboot_menu_is_7sec_reset
debug_level: 0x00004f4c (20300)
   pwron-ap: 0x00010000 (hard reset)
 pwron-pmic: 0x00000008 (mrst)
s5p_reboot_menu_is_7sec_reset: 7sec reset at low debug level
cmu_div:65535, div:1, src_clk:0, pixel_clk:15552000
reset_lcd by s6e36w1x01
s5p_dsim_display_config: COMMAND MODE
display id: 40, 20, 15
s5p_reboot_menu_is_7sec_reset: timeout
target reboot with swreset as workaround
s5p_restart_handler ('N':normal)

OMUIC rev = MAX14577(117)
MON: 0x65(4)
MON[0] = (4)[0x37, 0xe8]
MON[1] = (5)[0x39, 0xe8]
MON[2] = (6)[0x3a, 0xc0]
MON[3] = (7)[0x0c, 0x14]
MON[4] = (0)[0x36, 0xe8]
MON[5] = (1)[0x32, 0xfc]
MON[6] = (2)[0x18, 0x20]
MON[7] = (3)[0x0a, 0x00]
cardtype: 0x00000007
buswidth: 0x00
hstiming: 0x00
SB_MMC_HS_52MHZ_1_8V_3V_IO
mmc->card_caps: 0x00000f11
mmc->host_caps: 0x00000f11
!!!Enter 8 Bit DDR mode.!!!
[mmc] capacity = 7634944

MODEL_NAME:{{SM-R732}}
eMMC_SERIAL_NUMBER:{{150100464A32354441008825557FC261}}