Layout of In-system Program Image File: ISPBOOOT.BIN

This article explain the layout of in-system program image file, ISPBOOOT.BIN, of SP7350.

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 setup by boot-switch of SP7350, or in root directory of USB flash drive if “boot from USB flash drive” is setup by boot-switch of SP7350. Once found the file, it loads the first-stage boot loader, called x-boot, from it and store to 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 loaded U-Boot image from offset 0x30000 of ISPBOOOT.BIN. If checksum is verified pass, it then jumps to run U-Boot.

U-Boot then run scripts for programming flash device, such as eMMC, SPI-NAND flash, 8-bit NAND flash or SPI-NOR flash.

Refer to figure below,

The following table explain use of each partitions.

Refer to code below for definition of 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));

#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