Page Comparison

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The "iboot_main" subroutine commences by invoking the "init_cdata" subroutine to initialize global C data. It then proceeds to read boot-strap pins from a dedicated hardware register, storing the information in the C structure "g_bootinfo". In the event of a warm-boot scenario, it checks the readiness of DRAM (where CM4 handles the restoration of DDR IO retention data and specific hardware registers or settings). If DRAM is confirmed ready, the subroutine redirects to the start address of the warm-boot module to continue the warm-boot processes.

In cases where a warm-boot is not applicable (in cold-start scenario), the process continues to execute the "AV1_STC_init()", "init_uart()", and "init_hw()" subroutines to initialize hardware components. Finally, it advances to run the "boot_flow()" subroutine.

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The "boot_flow()" subroutine begins by examining the C structure g_bootinfo to determine the preferred boot device: eMMC, SPI-NAND flash, 8-bit NAND flash, SD card, or USB flash drive. It then initializes the controller of the selected boot device and loads the x-boot image into SRAM from the chosen source. After loading, the subroutine checks the image checksum. If the checksum passes verification, it proceeds to execute x-boot.

In the case of secure-boot activation through OTP bits, the subroutine additionally checks the digital signature and decrypts the image after the checksum validation.

It's essential to note that i-boot does not initialize DDR DRAM, rendering it temporarily unavailable. Hence, x-boot must be loaded into SRAM for execution.

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Device drivers

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