Getting Started with CM4

development

Prepare

1. Prepare a usb-serial cable, a 5V/3A adaptor type-c power supply. The serial cable is used for console debug and type-c cable is used for android image download and ADB debug.

2. Prepare a SDcard at least 8GB for linux development, android only support emmc boot.

3. The SOC rom first boot media is emmc, so board can't bootup from SDcard if the emmc is bootable with any image flashed, more info please refer to board boot sequence.

Android

Prepare

1. Download and install the AML Usb Burning Tool for android image download via type-c, only support windows.

2. Download the latest android image, and confirm that the md5 checksum is correct.

Install Image with Usb Burning Tool

1. Open USB_Burning_Tool.exe, select menu File->Import image, choose the android image file aml_upgrade_package.img.

2. Press and hold USB button on the board, plugin type-c usb cable to PC or press the RST button if power adapter already connected, about two seconds later, release the button, the board will be identified correctly.

3. Click the Start button of the download tool and wait for upgrade complete.

4. After Burning successfull, Unplug the type-c usb and connect to power supply adaptor to startup.

5. Click the Stop button to cancel the upgrade process and close the USB Buring Tool.

Install Image with Aml Flash Tool

aml-flash-tool is a linux platform opensource image flash util for Amlogic android.

 $ ./flash-tool.sh --img=/path/to/aml_upgrade_package.img --parts=all --wipe --soc=g12a --reset=y

Build Android Source Code

1. Get Android 9.0 source code

 $ https://github.com/BPI-SINOVOIP/BPI-A311D-Android9

2. Build the Android 9.0 Source code

Please read the source code README.md

Android DTB overlay

Bananapi CM4 DTBO idx value table, default idx value is 0 in release image.

Bananapi CM4 DTBO idx value table
idx value	device tree overlay	description
0	android_p_overlay	default dtbo, no use
1	wifi_bt_rtl8822cs	enable bpi rtl8822cs wifi/bt module
2	i2c1	enable i2c 1
3	i2c2	enable i2c 2
4	sdio	enable sdio
5	uart1	enable 2 pins uart 1
6	uart1_cts_rts	enable 4 pins uart 1
7	uart2	enable 2 pins uart 2
8	hifi_pcm5122	enable i2s pcm5122 HiFi DAC

How to apply a new dtbo

1. ADB command via sysfs

 root@dangku-desktop:/tmp# adb root
 restarting adbd as root
 root@dangku-desktop:/tmp# adb remount
 remount succeeded
 root@dangku-desktop:/tmp# adb shell
 bananapi_m2s:/ # echo dtbo > /sys/class/unifykeys/name                                                
 bananapi_m2s:/ # echo "1" > /sys/class/unifykeys/write                                                
 bananapi_m2s:/ # reboot

2. Uart console command via sysfs

 console:/ $ 
 console:/ $ su
 console:/ # echo dtbo > /sys/class/unifykeys/name                              
 [  115.702781@0] unifykey: name_store() 1302, name dtbo, 4
 [  115.702856@0] unifykey: name_store() 1311
 console:/ #
 console:/ # echo "1" > /sys/class/unifykeys/write                              
 [  129.262659@0] unifykey: write_store()  is a string
 [  129.262733@0] unifykey: dtbo, 1, 1
 [  129.265312@0] unifykey: amlkey_write 393
 [  129.292347@1] emmc_key_write:149, write ok
 console:/ # 
 console:/ # reboot

3. Settings App(To-Do)

Check the bootup uart debug message and confirm which dtbo is loaded actually, here "1" means set idx=1 to apply wifi_bt_rtl8822cs dtbo.

 load dtb from 0x1000000 ......
       Amlogic multi-dtb tool
       Single dtb detected
 find 2 dtbos
 dtbos to be applied: 1
 Apply dtbo 1

Unifykeys is stored in a specific emmc part, "Normal erase" selected in USB_Burning_Tool will not erase this data for next update, you must select "Erase all" if you want the default dtbo idx to be applied after image download.

Build Android image with a specific DTBO default.

1. Default build-in overlays are defined in device/bananapi/bananapi_m2s/Kernel.mk, you can add a new overlay dtbo here.

 DTBO_DEVICETREE := android_p_overlay wifi_bt_rtl8822cs i2c1 i2c2 sdio uart1 uart1_cts_rts uart2 hifi_pcm5122

2. Default apply DTBO idx is defined in device/bananapi/bananapi_m2s/BoardConfig.mk, you can change the idx value to set which overlay dtbo will be applied default.

 BOARD_KERNEL_CMDLINE += androidboot.dtbo_idx=0

3. DTS files are in common/arch/arm64/boot/dts/amlogic/overlay/bananapi_m2s/

More info about android device tree overlays, please refer to google android offical site

Install OpenGapps

1. Download install package from OpenGapps, Android release image is arm/android 9.0 variant.

2. Download device_id.apk.

3. Copy the OpenGapp package to a udisk or sdcard root directory.

4. Create a txt file named factory_update_param.aml in udisk or sdcard root directory with the following android recovery parameter content, and replace the file name with the actual downloaded package.

udisk:

 --wipe_cache
 --update_package=/udisk/open_gapps-arm-9.0-pico-20210327.zip

sdcard:

 --wipe_cache
 --update_package=/sdcard/open_gapps-arm-9.0-pico-20210327.zip

5. Plugin the udisk or sdcard to the board and poweron.

6.OpenGapps install and certify.

watch this video on bilibili

Switch Mipi Panel

The default android release image only support one mipi panel because hw has no detect logic for different panel at boot, so [800x1280 bpi panel] enabled as default, but you can change to [1200x1920 bpi panel] as defualt in Settings->Panel Output

Panel Rotation

The two 10" mipi panels are all portrait hw display, so the default android release image is portrait mode, but you can rotate it to 90/180/270 in two ways.

1. UI Rotation in Settings->Display->Screen rotation

2. SurfaceFlinger rotation, need modify android source code and build

Change the default sf rotation property

   diff --git a/device/bananapi/bananapi_m2s/bananapi_m2s.mk b/device/bananapi/bananapi_m2s/bananapi_m2s.mk
   index 1f51703..d592a44 100644
   --- a/device/bananapi/bananapi_m2s/bananapi_m2s.mk
   +++ b/device/bananapi/bananapi_m2s/bananapi_m2s.mk
   @@ -579,6 +579,6 @@ PRODUCT_PROPERTY_OVERRIDES += \
    else
    PRODUCT_PROPERTY_OVERRIDES += \
        ro.sf.lcd_density=213 \
    -    ro.sf.primary_display_orientation=0
   +    ro.sf.primary_display_orientation=90
    endif

Change the touch panel rotation in dts

   diff --git a/common/arch/arm64/boot/dts/amlogic/bananapi_m2s.dts b/common/arch/arm64/boot/dts/amlogic/bananapi_m2s.dts
   index 4a698b0..3d41b63 100755
   --- a/common/arch/arm64/boot/dts/amlogic/bananapi_m2s.dts
   +++ b/common/arch/arm64/boot/dts/amlogic/bananapi_m2s.dts
   @@ -876,8 +876,8 @@
                   reg = <0x5d>;
                   reset-gpio = <&gpio GPIOA_6 GPIO_ACTIVE_HIGH>;
                   irq-gpio = <&gpio GPIOA_5 GPIO_ACTIVE_HIGH>;
   -               rotation = <4>; /* sf_rotation 0 */
   -               //rotation = <0>; /* sf_rotation 90*/
  +               //rotation = <4>; /* sf_rotation 0 */
  +               rotation = <0>; /* sf_rotation 90*/
                   //rotation = <5>; /* sf_rotation 180 */
                   //rotation = <3>; /* sf_rotation 270 */

Custom Android Boot Logo

Android bootloader limit boot logo fb display size is 1080p60hz/1920x1080 default, and android kernel dtb partition table limit boot logo partition size to 16MB default .

1. Prepare a 16bit bmp file and named boot-logo.bmp

2. Compress the bmp file to boot-logo.bmp.gz

 $ gzip boot-logo.bmp

3. Download m2s_android_bootlogo_tool.zip

4. Extract this tool

 $ unzip m2s_android_bootlogo_tool.zip
 $ cd m2s_android_bootlogo_tool/
 $ ls -l logo/
 -rwxr--r-- 1 dangku dangku 525054 Sep 25 16:54 bootup.bmp
 -rwxr--r-- 1 dangku dangku 525054 Sep 25 16:54 bootup_secondary.bmp
 -rwxr--r-- 1 dangku dangku    184 May 19  2020 upgrade_bar.bmp
 -rwxr--r-- 1 dangku dangku 180072 May 19  2020 upgrade_error.bmp
 -rwxr--r-- 1 dangku dangku 180072 May 19  2020 upgrade_fail.bmp
 -rwxr--r-- 1 dangku dangku 180072 May 19  2020 upgrade_logo.bmp
 -rwxr--r-- 1 dangku dangku 180072 May 19  2020 upgrade_success.bmp
 -rwxr--r-- 1 dangku dangku    184 May 19  2020 upgrade_unfocus.bmp
 -rwxr--r-- 1 dangku dangku 180072 May 19  2020 upgrade_upgrading.bmp

5. Copy the boot-logo.bmp.gz

 $ cp boot-logo.bmp.gz logo/bootup.bmp
 $ cp boot-logo.bmp.gz logo/bootup_secondary.bmp

6. Create target logo.img with img pack tool, the binary and related libs of m2s_android_bootlogo_tool are copy from <android-source-dir>/out/host/linux-x86

 $ ./logo_img_packer -r logo logo.img

7. Flash boot logo with fastboot

 $ adb root
 $ adb remount
 $ adb reboot fastboot

Wait few seconds and check whether fastboot connected

 $ fastboot device
 1234567890      fastboot
 $ fastboot flashing unlock_critical
 $ fastboot flashing unlock
 $ fastboot flash logo logo.img
 $ fastboot reboot

Linux

Prepare

1. Linux image support SDcard or EMMC bootup, but you should read the boot sequence at first.

2. Make sure bootable EMMC is formatted if you want bootup from SDcard, more info refer to Erase EMMC for SDcard Bootup

3. Make sure SDcard is formatted without Linux image flashed if you want bootup from EMMC and use Sdcard as storage.

4. Install bpi-tools on your Linux PC(if flash image with other tools, ignore this step). If you can't access this URL or any other install problem, please go to bpi-tools source repo, download and install this tools manually.

 $ apt-get install pv
 $ curl -sL https://github.com/BPI-SINOVOIP/bpi-tools/raw/master/bpi-tools | sudo -E bash

5. Download Linux latest Linux Image, and confirm that the md5 checksum is correct.

6. Default login: pi/bananapi or root/bananapi

Install Image to SDcard

1. Install Image with Etcher on Windows, Linux and MacOS.

Balena Etcher is an opensource GUI flash tool by Balena, Flash OS images to SDcard or USB drive

2. Install Image with dd command on Linux, umount SDcard device /dev/sdX partition if mounted automatically. Actually bpi-copy is the same as this dd command.

 $ sudo apt-get install pv unzip
 $ sudo unzip -p xxx-bpi-cm4-xxx.img.zip | pv | dd of=/dev/sdX bs=10M status=noxfer

3. Install the linux image in udisk with bpi-tools on Linux, plug SDcard to Linux PC and run

 $ sudo apt-get install pv unzip
 $ sudo bpi-copy xxx-bpi-cm4-xxx.img.zip /dev/sdX

Install Image to EMMC

1. Prepare a SDcard with Linux image flashed and bootup board with this SDcard.

2. Copy Linux image to udisk, plug the udisk to board and mount it.

3. Install with dd command, umount mmcblk0p1 and mmcblk0p2 partition if mounted automatically. Actually bpi-copy is the same as this dd command.

 $ sudo apt-get install pv unzip
 $ sudo unzip -p xxx-bpi-cm4-xxx.img.zip | pv | dd of=/dev/mmcblk0 bs=10M status=noxfer

4. Install with bpi-tools command

 $ sudo apt-get install pv unzip
 $ sudo bpi-copy xxx-bpi-cm4-xxx.img.zip /dev/mmcblk0

5. After download complete, power off safely and eject the SDcard.

Build Linux Source Code

1. Get the Linux bsp source code

 $  git clone https://github.com/BPI-SINOVOIP/BPI-M2S-bsp

2. Build the bsp source code

Please read the source code README.md

3. If you want build uboot and kernel separately, please download the u-boot the kernel only, get the toolchains, boot script and other configuration files from BPI-M2S-bsp

DTB overlay

1. DTB overlay is used for 40pin gpios multi-function configuration and install in vfat boot partition, you can check the mount point with mount command.

 root@bananapi:~# ls /boot/overlays/
 hifi_pcm5122.dtbo  pdmmic.dtbo        sdio.dtbo                 waveshare_tft24_lcd.dtbo
 i2c1.dtbo          pwm_c-beeper.dtbo    spi0.dtbo                 waveshare_tft35c_lcd.dtbo
 i2c2.dtbo          pwm_cd-c.dtbo           spi0_flash.dtbo        wifi_bt_rtl8822cs.dtbo
 i2s.dtbo            pwm_cd.dtbo              uart1_cts_rts.dtbo    i2smic.dtbo    pwm_ef.dtbo 
 uart1.dtbo        os08a10.dtbo              pwm_ef-f.dtbo          uart2.dtbo

2. Update the overlays env in vfat /boot/env.txt to enable what you want.

 # Device Tree Overlays
 #   uart1           -- Enable UART1 (uart_A, GPIO Header PIN8 & PIN10)
 #   pwm_c           -- Enable PWM_C (GPIO Header PIN7)
 #   i2c2            -- Enable i2c2 (GPIO Header PIN3 & PIN5)
 #   spi0            -- Enable SPI0 (GPIO Header PIN19 & PIN21 & PIN23 & PIN24)
 overlays="i2c2 spi0 uart1"

3. Must be restart the board for overlay dtb loaded.

Enable Camera

The linux release image is camera disabled default, according to the following configuration, it can be enabled by yourself.

1. Update the dtb overlays env in /boot/env.txt to enable camera dtbo.

 overlays="os08a10"

2. Add camera modules to /etc/modules

 iv009_isp_iq
 iv009_isp_lens
 iv009_isp_sensor
 iv009_isp

3. Create and add camera modules options to /etc/modprobe.d/os08a10.conf

 #choose camera calibration parameters
 options iv009_isp_iq cali_name=0
 #choose isp register sequence
 options iv009_isp_sensor isp_seq_num=0

4. Enable camera isp systemd service

 $ sudo systemctl enable camera_isp_3a_server.service

Camera device is /dev/video0 after reboot.

Switch Mipi Panel

The default linux release image only support one mipi panel because hw has no detect logic for different panel at boot, so 800x1280 bpi panel enabled as default, but you can change to [1200x1920 bpi panel] as defualt in /boot/lcd_env.txt

 # Mipi panel type
 #    Symbol    | Resolution
 # ----------------------+-------------
 #    "lcd_0"   | 10" 800x1280 panel
 #    "lcd_1"   | 10" 1200x1920 panel
 panel_type=lcd_0

Note: Dual display is not work on linux, so disconnect hdmi cable when mipi used.

Panel Rotation

The two 10" mipi panels are all portrait hw display, so the default release image is portrait mode, but you can rotate it to 90/180/270.

For Desktop image, create a xorg configuration file /usr/share/X11/xorg.conf.d/10-fbdev-rotate.conf with contents:

 Section "Device"
     Identifier "Configured Video Device"
     # Rotate off
 #   Option "Rotate" "off"
     # Rotate Right / clockwise, 90 degrees
     Option "Rotate" "CW"
     # Rotate upside down, 180 degrees
 #   Option "Rotate" "UD"
     # Rotate counter clockwise, 270 degrees
 #   Option "Rotate" "CCW"
 
 EndSection
 
 Section "InputClass"
     Identifier "Coordinate Transformation Matrix"
     MatchIsTouchscreen "on"
     MatchProduct "goodix-ts"
     MatchDevicePath "/dev/input/event0"
     MatchDriver "libinput"
     # Rotate Right / clockwise, 90 degrees 
     Option "CalibrationMatrix" "0 1 0 -1 0 1 0 0 1"
     # Rotate upside down, 180 degrees
 #   Option "CalibrationMatrix" "-1 0 1 0 -1 1 0 0 1"
     # otate counter clockwise, 270 degrees 
 #   Option "CalibrationMatrix" "0 -1 1 1 0 0 0 0 1"
 
 EndSection

For Server image, you can change the framebuffer rotation in two ways:

1. Sysfs dynamically change.

 echo 0 > /sys/class/graphics/fbcon/rotate    //origin 0 degree
 echo 1 > /sys/class/graphics/fbcon/rotate    //90 degree
 echo 2 > /sys/class/graphics/fbcon/rotate    //180 degree
 echo 3 > /sys/class/graphics/fbcon/rotate    //270 degree

2. Boot Configuration change.

change the fb_rotate env in /boot/env.txt

 # Framebuffer Rotate
 # 0 - origin 0 degree
 # 1 - 90 degree
 # 2 - 180 degree
 # 3 - 270 degree
 fb_rotate=0

WiringPi

Note: This WiringPi only support set 26pin gpio to output, input, pwm or software pwm, for io functions as i2c, spi, ..., you must enable dtb overlay in boot.ini

1. Build and install wiringPi

 $ git clone https://github.com/Dangku/amlogic-wiringPi
 $ cd amlogic-wiringPi
 $ chmod a+x build
 $ sudo ./build

2. Run gpio readall to show all 40pins status.

3. BPI GPIO Extend board and examples in amlogic-wiringPi/examples

blinkall, blink all pin header gpios, no extend board.

lcd1602-pi, BPI LCD 1602 display module example.

52pi-bpi, BPI OLED Display Module example.

matrixled-bpi, BPI RGB LED Matrix Expansion Module example.

berryclip-bpi, BPI BerryClip Module

RPi.GPIO

Build and install

 $ sudo apt-get Install build-essential python python-dev python-setuptools git
 $ git clone https://github.com/Dangku/RPi.GPIO-Amlogic.git
 $ cd RPi.GPIO-Amlogic
 $ sudo python setup.py clean --all
 $ sudo python setup.py build install

WiringPi2-Python

Build and install

 $ sudo apt-get Install python python-dev python-setuptools swig git
 $ git clone --recursive  https://github.com/Dangku/WiringPi2-Python-Amlogic.git
 $ cd WiringPi2-Python-Amlogic
 $ sudo python setup.py install

Custom Linux Boot Logo

Linux uboot limit boot logo fb size to 1080p60hz/1920x1080 default, so oversize resolution will not be supported by default image, but you can modify uboot source code to support it.

1. Prepare a 24bit bmp file and named boot-logo.bmp

2. copy the target file to /boot/firmware/ or /boot/ directory.

EC20 LTE 4G Module

1. AT test

After the module is connected and Linux OS bootup. several ttyUSB* device files are created in the directory /dev. For EC20, /dev/ttyUSB2 is the AT port.

2. Connect Network via qmi_wwan on Ubuntu Desktop

Click edit connections in network manager menu

Add a new mobile broadband connection

Choose qmi channel device

When the qmi_wwan_q driver has been installed in the module, a network device and a QMI channel are created. The network device is named as wwanX and the QMI channel is /dev/cdc-wdmX. The network device is used for data transmission, and QMI channel is used for QMI message interaction

Choose carrier provider's country region

Choose carrier provider.

Set connection name, carrier connection username/password and APN if needed.

Setup finished, now you can connect it.

3. Connect Network via pppd on Ubuntu&Debian Server

Install pppd

 $ sudo apt install ipppd

Change AT device, username and password to your local carrier in /etc/ppp/peers/quectel-ppp

Change APN to your local carrier in /etc/ppp/peers/quectel-chat-connect

Two ways command to start pppd, you can check the process of PPP calling setup log here.

 # pppd call quectel-ppp &

or

 # quectel-pppd.sh /dev/ttyUSB2 <apn> <username> <password>

Terminate pppd process:

 # quectel-ppp-kill

4. Connect Network via qmi_wwan on Ubuntu&Debian Server

[quectel-CM] is a connection manager program for you to set up data connection manually. You can check the process of qmi_wwan calling setup log here.

 # quectel-CM &

Terminate quectel-CM process:

 # killall quectel-CM

Boot Linux from SSD

A311d soc rom and BPI-M2S-bsp uboot are both not support nvme boot, so the only way for booting linux from SSD is create a bootable sdcard or emmc with bootloader and boot partition flashed, then load rootfs from SSD. After bootup, everything will run from SSD. You need a minipcie to nvme adapter board because bananapi cm4io has a minipcie slot onboard.

1. The simple way is flash the CM4 Linux image to sdcard or emmc for bootable and also flash it to the nvme ssd for loading rootfs.

2. Bootup the CM4 board with sdcard or emmc, modify /boot/boot.ini to load rootfs from nvme partition for kernel.

 diff a/boot/boot.ini b/boot/boot.ini
 index 2222e79..c485067 100755
 --- a/boot/boot.ini
 +++ b/boot/boot.ini
 @@ -20,6 +20,8 @@ fi;

  if test "${devtype}" = "usb"; then setenv rootfsdev "/dev/sda2"; fi

 +# force set root=/dev/nvme0n1p2
 +setenv rootfsdev "/dev/nvme0n1p2"
 +
  # Load env.txt
  fatload ${devtype} ${devno}:1 ${env_loadaddr} env.txt
  env import -t ${env_loadaddr} ${filesize};

3. Reboot the system, kernel will load rootfs from nvme ssd.

4. Test performance

You can verify the performance of your SSD on Pi Benchmarks using the following command:

 sudo curl https://raw.githubusercontent.com/TheRemote/PiBenchmarks/master/Storage.sh | sudo bash

Test results for sd, emmc and nvme ssd (Samsung 970EVOPlus)

Category	Test	Sdcard Test Result	Emmc Test Result	Nvme SSD Test Result
HDParm	Disk Read	60.67 MB/s	148.80 MB/s	351.29 MB/s
HDParm	Cached Disk Read	56.71 MB/s	141.02 MB/s	347.03 MB/s
DD	Disk Write	14 MB/s	51.0 MB/s	244 MB/s
FIO	4k random read	2176 IOPS (8704 KB/s)	8438 IOPS (33753 KB/s)	101386 IOPS (405544 KB/s)
FIO	4k random write	932 IOPS (3729 KB/s)	10876 IOPS (43505 KB/s)	43206 IOPS (172827 KB/s)
IOZone	4k read	8586 KB/s	20311 KB/s	119475 KB/s
IOZone	4k write	2385 KB/s	19016 KB/s	90619 KB/s
IOZone	4k random read	6734 KB/s	20807 KB/s	51517 KB/s
IOZone	4k random write	3737 KB/s	22731 KB/s	95139 KB/s
		Score: 1076	Score: 5446	Score: 24550

Other Development

Boot Sequence

Check bootloader loaded from SDcard or EMMC at the beginning of the console debug messages

1. Rom load bootloader from SDcard (Linux log example)

 ...
 
 BL2 Built : 15:21:42, Mar 26 2020. g12a g486bc38 - gongwei.chen@droid11-sz
 
 Board ID = 1
 Set cpu clk to 24M
 Set clk81 to 24M
 Use GP1_pll as DSU clk.
 DSU clk: 1200 Mhz
 CPU clk: 1200 MHz
 Set clk81 to 166.6M
 board id: 1
 Load FIP HDR DDR from SD, src: 0x00010200, des: 0xfffd0000, size: 0x00004000, part: 0
 fw parse done
 PIEI prepare done
 fastboot data verify
 result: 255
 Cfg max: 12, cur: 1. Board id: 255. Force loop cfg
 DDR4 probe
 
 ...

2. Rom load bootloader from EMMC(Android Log example)

 ...
 
 Board ID = 1
 Set cpu clk to 24M
 Set clk81 to 24M
 Use GP1_pll as DSU clk.
 DSU clk: 1200 Mhz
 CPU clk: 1200 MHz
 Set clk81 to 166.6M
 eMMC boot @ 0
 sw8 s
 board id: 1
 Load FIP HDR DDR from eMMC, src: 0x00010200, des: 0xfffd0000, size: 0x00004000, part: 0
 fw parse done
 PIEI prepare done
 00000000
 emmc switch 1 ok
 ddr saved addr:00016000
 Load ddr parameter from eMMC, src: 0x02c00000, des: 0xfffd0000, size: 0x00001000, part: 0
 00000000
 
 ...

Erase EMMC for SDcard Bootup

There are four possible scenarios should be pay attention to, EMMC already flashed Android image, EMMC already flashed Linux image, boot process hangup in BL2 and EMMC empty.

1. Bootable EMMC with Android image flashed

a). Using usb burning tool, unplug the type-c usb cable while the download process at 7% formatting

b). Using Android Fastboot tool, make sure the adb/fastboot tools is work on your PC before doing this.

   root@dangku-desktop:/tmp# adb root
   adbd is already running as root
   root@dangku-desktop:/tmp# adb remount
   remount succeeded
   root@dangku-desktop:/tmp# adb shell
   bananapi_m2s:/ # reboot fastboot

Wait a few seconds for board reboot to fastboot mode

   root@dangku-desktop:/tmp# fastboot devices
   1234567890	fastboot
   root@dangku-desktop:/tmp# fastboot flashing unlock_critical
   ...
   OKAY [  0.044s]
   finished. total time: 0.044s
   root@dangku-desktop:/tmp# fastboot flashing unlock
   ...
   OKAY [  0.047s]
   finished. total time: 0.047s
   root@dangku-desktop:/tmp# fastboot erase bootloader
   erasing 'bootloader'...
   OKAY [  0.059s]
   finished. total time: 0.059s
   root@dangku-desktop:/tmp# fastboot erase bootloader-boot0
   erasing 'bootloader-boot0'...
   OKAY [  0.036s]
   finished. total time: 0.036s
   root@dangku-desktop:/tmp# fastboot erase bootloader-boot1
   erasing 'bootloader-boot1'...
   OKAY [  0.035s]
   finished. total time: 0.035s

c). Using uboot command, connect a debug console cable and press ESC while power on to enter uboot command line

   bananapi_m2s_v1#amlmmc erase 1
   emmckey_is_protected(): protect
   start = 0,end = 57343
   start = 221184,end = 30535679
   Erasing blocks 0 to 8192 @ boot0
   start = 0,end = 8191
   Erasing blocks 0 to 8192 @ boot1
   start = 0,end = 8191
   bananapi_m2s_v1#reset
   resetting ...
   SM1:BL:511f6b:81ca2f;FEAT:A0F83180:20282000;POC:F;RCY:0;EMMC:0;READ:0;CHK:1F;READ:0;CHK:1F;READ:0;CHK;

These two ways actually erase the bootloader part of EMMC android, After bootup from SDcard Linux, You'd better format the whole EMMC by dd command.

d). The simplest way is insert the SDcard with Linux image flashed before power on, the Android bootloader will check boot.ini file whether exist in SDcard vfat partition, so that the SDcard Linux will bootup. After bootup, you can format the whole EMMC by dd command and then flash the Linux image to EMMC.

   ...
   BPI: try boot from sdcard
   reading boot.ini
   2453 bytes read in 3 ms (797.9 KiB/s)
   ## Executing script at 03080000
   Starting boot.ini...
   reading env.txt
   3483 bytes read in 7 ms (485.4 KiB/s)
   HDMI: Autodetect: 1080p60hz
   reading Image.gz
   10924573 bytes read in 611 ms (17.1 MiB/s)
   reading bananapi_m2s.dtb
   88054 bytes read in 12 ms (7 MiB/s)
   reading uInitrd
   11704481 bytes read in 655 ms (17 MiB/s)
   reading overlays/wifi_bt_rtl8822cs.dtbo
   729 bytes read in 6 ms (118.2 KiB/s)

2. Bootable EMMC with Linux image flashed

a). Using uboot command, connect a debug console cable and press ESC while power on to enter uboot command line

   bananapi_m2s# mmc erase 0 1000

b). Linux u-boot also check boot.ini file whether exist in SDcard vfat partition so that the SDcard Linux will bootup. After bootup, you can format the whole EMMC by dd command or flash the Linux image directly to EMMC.

3. A extreme situation is bootloader or uboot corrupted, Rom load it from EMMC but hangup in u-boot or BL2, for example the boot process will hangup in BL2 of EMMC if dram init failed, The only way is format the EMMC with usb burning tool, or download the Android image completely and then try other ways to erase EMMC or flash Linux image to EMMC.

4. Rom will try to load bootloader from SDcard directly if EMMC is empty.

Erase Emmc Android by dd command

If the board is flashed android before, the whole emmc must be erased by these commands if you want bootup it with SDcard Linux image.

 $ sudo dd if=/dev/zero of=/dev/mmcblk0boot0 bs=1M status=noxfer 
 $ sudo dd if=/dev/zero of=/dev/mmcblk0boot1 bs=1M status=noxfer
 $ sudo dd if=/dev/zero of=/dev/mmcblk0 bs=1M status=noxfer 
 $ sync

Cloud-init&Snap

Cloud-init and Snap service are enabled default, you can disable or remove them.

1. disable or remove cloud-init

 $ sudo touch /etc/cloud/cloud-init.disabled

or

 $ sudo apt purge cloud-init

2. disable or remove snap

 $ sudo apt purge snapd

Enable rc-local

The systemd service rc-local.service already exists in release image, but there is no [Install] part in the unit file. As a result, Systemd is unable to enable it. First, we must update the file.

 $ sudo nano /lib/systemd/system/rc-local.service

 [Unit]
 Description=/etc/rc.local Compatibility
 Documentation=man:systemd-rc-local-generator(8)
 ConditionFileIsExecutable=/etc/rc.local
 After=network.target
 
 [Service]
 Type=forking
 ExecStart=/etc/rc.local start
 TimeoutSec=0
 RemainAfterExit=yes
 GuessMainPID=no
 
 [Install]
 WantedBy=multi-user.target
 Alias=rc-local.service

Create /etc/rc.local file.

 sudo nano /etc/rc.local

 #!/bin/sh
 #
 # rc.local
 #
 # This script is executed at the end of each multiuser runlevel.
 # Make sure that the script will "exit 0" on success or any other
 # value on error.
 #
 # In order to enable or disable this script just change the execution
 # bits.
 #
 # By default this script does nothing.
 
 exit 0

Add executable permission to /etc/rc.local

 $ sudo chmod +x /etc/rc.local

Enable rc-local.service and reboot

 $ sudo systemctl enable rc-local.service
 $ sudo reboot

Enable sudo for Debian

The release Debian image do not install sudo default, with "su -" command, user can change to root. If you like sudo, you can install it.

 $ su -
 Password:(enter bananapi)
 
 # apt install sudo
 # adduser pi sudo

Then please do logout and login again

Install Docker Engine

Install Docker Engine on Ubuntu 20.04 Server

1. Set up the repository

Update the apt package index and install packages to allow apt to use a repository over HTTPS:

 $ sudo apt-get update
 $ sudo apt-get install apt-transport-https ca-certificates curl gnupg lsb-release

Add Docker’s official GPG key:

 $ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

Set up the stable repository

 $  echo \
    "deb [arch=arm64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
    $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

2. Install Docker Engine

 $ sudo apt-get update
 $ sudo apt-get install docker-ce docker-ce-cli containerd.io

3. Verify the Docker Engine is installed correctly by running the hello-world image.

 $ sudo docker run hello-world

Install docker with a simple command

 $ curl -sSL get.docker.com | sudo sh

Install Docker Engine on other Linux distributions