4.4. Android on SD Card

This application note contains steps to use SD Card instead of eMMC.

4.4.1. Build U-Boot with this changes

Follow this link to download the Downloading sources.

Apply this patch in U-Boot source code:

diff --git a/configs/am62x_android_a53.config b/configs/am62x_android_a53.config
index fc949f65d7fe..d50952557192 100644
--- a/configs/am62x_android_a53.config
+++ b/configs/am62x_android_a53.config
@@ -5,7 +5,7 @@ CONFIG_USB_FUNCTION_FASTBOOT=y
CONFIG_FASTBOOT_BUF_ADDR=0xC0000000
CONFIG_FASTBOOT_BUF_SIZE=0x2F000000
CONFIG_FASTBOOT_FLASH=y
-CONFIG_FASTBOOT_FLASH_MMC_DEV=0
+CONFIG_FASTBOOT_FLASH_MMC_DEV=1
CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
# Enable Android boot flow
CONFIG_SYS_MALLOC_LEN=0x08000000

When using the the experimental 2024.04 U-Boot release apply this patch instead:

diff --git a/configs/am62x_a53_android.config b/configs/am62x_a53_android.config
index 55fa93b140f9..dd0d36069d74 100644
--- a/configs/am62x_a53_android.config
+++ b/configs/am62x_a53_android.config
@@ -5,7 +5,7 @@ CONFIG_USB_FUNCTION_FASTBOOT=y
 CONFIG_FASTBOOT_BUF_ADDR=0xC0000000
 CONFIG_FASTBOOT_BUF_SIZE=0x2F000000
 CONFIG_FASTBOOT_FLASH=y
-CONFIG_FASTBOOT_FLASH_MMC_DEV=0
+CONFIG_FASTBOOT_FLASH_MMC_DEV=1
 CONFIG_CMD_GPT=y # Needed for FASTBOOT_CMD_OEM_FORMAT
 CONFIG_RANDOM_UUID=y # Needed for FASTBOOT_CMD_OEM_FORMAT
 CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
diff --git a/include/env/ti/android.env b/include/env/ti/android.env
index a058beb7fc42..693806550853 100644
--- a/include/env/ti/android.env
+++ b/include/env/ti/android.env
@@ -24,8 +24,8 @@ partitions+=name=userdata,size=-,uuid=${uuid_gpt_userdata}
 fastboot_raw_partition_bootenv=0x800 0x400 mmcpart 1
 fastboot.partition-type:metadata=f2fs

-boot_targets=mmc0
-mmcdev=0
+boot_targets=mmc1
+mmcdev=1
 bootmeths=android
 vendor_boot_comp_addr_r=0xd0000000
 bootcmd=bootflow scan -lb

Follow this link to build the Build Instructions.

Rebuild U-Boot then copy u-boot.img in Android build system environment : vendor/ti/am62x/bootloader/am62px-sk

Follow this link to build Build Instructions. Go in your Android environment then rebuild with TARGET_SDCARD_BOOT=true build args:

$ cd ${YOUR_PATH}/ti-aosp-14
$ source build/envsetup.sh
$ lunch <BUILD_TARGET>
$ m TARGET_SDCARD_BOOT=true

Warning

Minimal size for SD card is 16GB

Go in out directory in android environment and launch this command:

$ cd out/target/product/am62p
$ sudo ./flashall.sh --board="am62px-sk" --sdcard="/dev/sdX"

flashall.sh script print in your console instruction to do

Tip

Replace X in /dev/sdX/ by letter corresponding to your SD card