This article explains the layout of partitions in the ISP file ISPBOOOT.BIN. The ISP (In-System Program) file for SP7350 to boot and write images to flash devices.
When the SP7350 powers on, its internal ROM code initiates a search for the ISPBOOOT.BIN file. The search location is the root directory of the first or solo partition on the selected boot devices, with options including an SD card or a USB flash drive. Once found, the file is loaded, extracting the first-stage boot loader, X-Boot, and storing it in the internal SRAM.
The X-Boot image, situated at offset 0 within ISPBOOOT.BIN, has a maximum size of 192 KiB, with the actual size recorded in the X-Boot image header. Upon successful checksum verification, the system transitions to execute X-Boot.
X-Boot initializes and trains the SDRAM controller, preparing the DRAM for use. Subsequently, it loads the TF-A (Trusted Firmware-A) and OP-TEE (Open Portable Trusted Execution Environment) images from the fip (firmware image package) partition within ISPBOOOT.BIN, storing them in DRAM. Additionally, the U-Boot image is extracted from offset 0x30000 of ISPBOOOT.BIN and stored in DRAM. Upon successful checksum verification for all images, the system proceeds to execute TF-A, followed by OP-TEE, and finally U-Boot.
U-Boot autonomously executes scripts to program one of the following flash devices: eMMC, SPI-NAND flash, 8-bit NAND flash, or SPI-NOR flash.
The partition layout of ISPBOOOT.BIN is illustrated below, commencing with the X-Boot image (partition name: xboot0), followed by the U-Boot image (partition name: uboot0), and a header detailing the subsequent partitions.
Note actual size is the file size aligned to 1k boundary.
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 variables of U-Boot |
env_redund | - | actual size | Image of environment variables 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 flash 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 flash in-system program |
Refer to the code below for the 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 the code below for the 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