u-boot/board/ste/stemmy

ST-Ericsson U8500 Samsung "stemmy" board
========================================

The "stemmy" board supports Samsung smartphones released with
the ST-Ericsson NovaThor U8500 SoC, e.g.

	- Samsung Galaxy S III mini (GT-I8190)	"golden"
	- Samsung Galaxy S Advance (GT-I9070)	"janice"
	- Samsung Galaxy Xcover 2 (GT-S7710)	"skomer"

and likely others as well (untested).

At the moment, U-Boot is intended to be chain-loaded from
the original Samsung bootloader, not replacing it entirely.

Installation
------------

1. Setup cross compiler, e.g. export CROSS_COMPILE=arm-none-eabi-
2. make stemmy_defconfig
3. make

For newer devices (golden and skomer), the U-Boot binary has to be packed into
an Android boot image. janice boots the raw U-Boot binary from the boot partition.

4. Obtain mkbootimg, e.g. https://android.googlesource.com/platform/system/core/+/refs/tags/android-7.1.2_r37/mkbootimg/mkbootimg
5. mkbootimg \
    --kernel=u-boot.bin \
    --base=0x00000000 \
    --kernel_offset=0x00100000 \
    --ramdisk_offset=0x02000000 \
    --tags_offset=0x00000100 \
    --output=u-boot.img

6. Enter Samsung download mode (press Power + Home + Volume Down)
7. Flash U-Boot image to Android boot partition using Heimdall:
     https://gitlab.com/BenjaminDobell/Heimdall

   heimdall flash --Kernel u-boot.(bin|img)

8. After reboot U-Boot prompt should appear via UART.

UART
----

UART is available through the micro USB port, similar to the Carkit standard.
With a ~619kOhm resistor between ID and GND, 1.8V RX/TX is available at D+/D-.

Make sure to connect the UART cable *before* turning on the phone.