[4412 development board tutorial] Uboot tutorial uboot basic concepts and framework

Knowledge points:

1. The concept of operating system layering

        Windows: bios → kernel mode → user mode → user program

        Linux: bootloader → kernel → file system → user program

2. Introduction to bootboader types

        U-boot is the most common bootboader. (210, 4412, etc.)

        vivi is used to customize 2440 for Samsung's ARM

3.4412 Sleep Problem

        It can skip uboot and run the system directly

Welcome to watch Xunwei's uboot video tutorial!

What have you done?

        1. What are these decompressed files used for?

        2. Compile

        3. Burning (DIP switch)

        4. Run uboot

Summary of the problem

        Question 1: What are the uses of uboot source code and other files?

        Question 2: What is the compilation process like?

        Question 3: How is burning achieved?

        Question 4: What is the matter with TF card startup and fastboot?

        Question 5: What will uboot do when it starts?

Tutorial ideas

        Preparation: At least watch the introductory part of the video, compile and burn, etc.

        1. Start with a problem

        2. Introduce new questions when answering these questions

        3. Expand your knowledge and concepts

        4. Please note that there is no particular order in which questions are answered.

Question: Why do we need uboot?

        Layered for easy transplantation.

Look with doubt: the part about uboot in the Datasheet

        New questions:

        iROM: short code, memory storage on the 4412 chip

                64KB

        New questions:

        BL1: First boot loader, they are on the extended memory

                BL1 is provided by Samsung and is not open source

        BL2：Second boot loader

                Not provided by Samsung. Has code.

        Useful knowledge:

        OM (DIP switch) is controlled by iROM

        BL1 needs the code in iROM to verify

Solve the "Problem 4" part through iROM

Android_Exynos4412_iROM_Secure_Booting_Guide_Ver.1.00.00

What iROM does

Turn off the watchdog, turn off the interrupt, turn off the memory management unit

Question 4.1: Where does the OM dip switch work?

        Answer: iROM

Question 4.2: How do the OM DIP switches correspond?

        Take TF card as an example. To start with TF card, the DIP switch should be set to 10.