Snapdragon 845

About this

This document describes the information about Qualcomm Snapdragon 845 supported boards and it’s usage steps.

SDM845 - hi-end qualcomm chip, introduced in late 2017. Mostly used in flagship phones and tablets of 2018.

The current boot flow support loading u-boot as an Android boot image via Qualcomm’s UEFI-based ABL (Android) Bootloader.

Installation

Build

Setup CROSS_COMPILE for aarch64 and build U-Boot for your board:

$ export CROSS_COMPILE=<aarch64 toolchain prefix>
$ make <your board name here, see Boards section>_defconfig
$ make

This will build u-boot.bin in the configured output directory.

Generate FIT image

See doc/uImage.FIT for more details

Pack android boot image

We’ll assemble android boot image with u-boot.bin instead of linux kernel, and FIT image instead of initramfs. Android bootloader expect gzipped kernel with appended dtb, so let’s mimic linux to satisfy stock bootloader.

Boards

starqlte

The starqltechn is a production board for Samsung S9 (SM-G9600) phone, based on the Qualcomm SDM845 SoC.

Steps:

Build u-boot:

$ export CROSS_COMPILE=<aarch64 toolchain prefix>
$ make starqltechn_defconfig
$ make

Create dump dtb:

workdir=/tmp/prepare_payload
mkdir -p "$workdir"
cd "$workdir"
mock_dtb="$workdir"/payload_mock.dtb

dtc -I dts -O dtb -o "$mock_dtb" << EOF
/dts-v1/;
/ {
        memory {
                /* We expect the bootloader to fill in the size */
                reg = <0 0 0 0>;
        };

        chosen { };
};
EOF

gzip u-boot:
```
gzip u-boot.bin
```

Append dtb to gzipped u-boot:

cat u-boot.bin.gz "$mock_dtb" > u-boot.bin.gz-dtb

Now we’ve got everything to build android boot image:

mkbootimg --base 0x0 --kernel_offset 0x00008000 \
--ramdisk_offset 0x02000000 --tags_offset 0x01e00000 \
--pagesize 4096 --second_offset 0x00f00000 \
--ramdisk "$fit_image" \
--kernel u-boot.bin.gz-dtb \
-o boot.img

Flash image with your phone’s flashing method.

More information can be found on the Samsung S9 page.

dragonboard845c

The dragonboard845c is a Qualcomm Robotics RB3 Development Platform, based on the Qualcomm SDM845 SoC.

Steps:

Build u-boot:

$ export CROSS_COMPILE=<aarch64 toolchain prefix>
$ make dragonboard845c_defconfig
$ make

Create dummy dtb:

workdir=/tmp/prepare_payload
mkdir -p "$workdir"
mock_dtb="$workdir"/payload_mock.dtb

dtc -I dts -O dtb -o "$mock_dtb" << EOF
/dts-v1/;
/ {
        #address-cells = <2>;
        #size-cells = <2>;

        memory@80000000 {
                device_type = "memory";
                /* We expect the bootloader to fill in the size */
                reg = <0 0x80000000 0 0>;
        };

        chosen { };
};
EOF

gzip u-boot:
```
gzip u-boot.bin
```

Append dtb to gzipped u-boot:

cat u-boot.bin.gz "$mock_dtb" > u-boot.bin.gz-dtb

A db845c.its file can be found in board/qualcomm/dragonboard845c/ directory. It expects a folder as db845c_imgs/ in the main directory containing pre-built kernel, dts and ramdisk images. See db845c.its for full path to images:
```
mkimage -f db845c.its db845c.itb
```

Now we’ve got everything to build android boot image:

mkbootimg --kernel u-boot.bin.gz-dtb --ramdisk db845c.itb \
--output boot.img --pagesize 4096 --base 0x80000000

Flash boot.img using db845c fastboot method:
```
sudo fastboot flash boot boot.img
```

More information can be found on the DragonBoard 845c page.