This article explains the layout of partitions in-system program image file ISPBOOOT.BIN of SP7350.
After power on, internal ROM code of SP7350 will search for the file named ISPBOOOT.BIN in root directory of SD card if “boot from SD card” is selected by boot-switch of SP7350, or in root directory of USB flash drive if “boot from USB flash drive” is selected by boot-switch of SP7350. Once found the file, it loads the first-stage boot loader, X-Boot, from the image file and store X-Boot image to internal SRAM. The X-Boot image is at offset 0 of ISPBOOOT.BIN and its size is 192 KiB at maximum. Actual size is recorded in header of x-boot image. If checksum is verified pass, it then jumps to run X-Boot.
X-Boot will first do SDRAM controller initialization and training. After completed, DRAM is ready for use. It loads TF-A image from fip partition from ISPBOOOT.BIN and store to DRAM. It loads U-Boot image from offset 0x30000 of ISPBOOOT.BIN and store to DRAM . If checksum of both images are verified pass, it then jumps to run TF-A and then U-Boot.
U-Boot then automatically run scripts for programming flash device, such as eMMC, SPI-NAND flash, 8-bit NAND flash or SPI-NOR flash.
Refer to layout of partitions of file ISPBOOOT.BIN below, the image file starts with X-Boot image (partition name: xboot0) and followed by U-Boot image (partition nam: uboot0). Then is followed by a header which records detailed name, offset, size and etc. of the following partitions.
The following table explains each partition.
Partitions | Offset | Size | Descriptions |
|---|---|---|---|
xboot0 | 0 | 192 kB | image of x-boot, including training firmware of DDR |
uboot0 | 0x30000 | 1344 kB | image of U-Boot |
file_header | 0x180000 | 16 kB | header for the following partitions |
xboot | 0x184000 | actual size | image of x-boot, including training firmware of DDR |
uboot1 | - | actual size | image of U-Boot |
uboot2 | - | actual size | image of U-Boot |
fip | - | actual size | image of fip, including TF-A and OP-TEE |
env | - | actual size | image of environment variable of U-Boot |
env_redund | - | actual size | image of environment variable of U-Boot (redundant) |
dtb | - | actual size | image of device-tree blob (not used) |
kernel | - | actual size | image of Linux kernel with U-Boot header |
rootfs | - | actual size | image of root file-system |
isp_script_nand | - | actual size | script of U-Boot for NAND in-system program |
isp_script_emmc | - | actual size | script of U-Boot for eMMC in-system program |
isp_script_nor | - | actual size | script of U-Boot for SPI-NOR in-system program |
Refer to code below for definition of partition_info in the file_header.
#define SIZE_FILE_NAME (32)
struct partition_info_s {
u08 file_name[SIZE_FILE_NAME]; // file name of source (basename only)
u08 md5sum[36];
u32 file_offset; // offset in output file
u64 file_size; // file size of the partition
u32 partition_start_addr; // partition's start address in NAND, there will be an offset added in U-Boot script ($isp_nand_addr_1st_part), less than 4GB is expected.
u64 partition_size; // reserved size for this partition, less than 4GB is expected.
u32 flags;
u32 emmc_partition_start; // Unit: block
u32 reserved[7]; // let size of this structure == SIZE_PARTITION_INFO_S
} __attribute__((packed));
Refer to code below for definition of file_header.
#define SIZE_PARTITION_INFO_S (128)
#define SIZE_INIT_SCRIPT (2048)
#define NUM_OF_PARTITION (111)
struct file_header_s {
u08 signature[32];
u08 init_script[SIZE_INIT_SCRIPT];
u32 flags;
u08 reserved[SIZE_PARTITION_INFO_S - 36];
struct partition_info_s partition_info[NUM_OF_PARTITION];
} __attribute__((packed)); // sizeof(this structure) == 16384