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¶ About This Manual
¶ Introduction
This document mainly describes the boot flow, the boot sources available for the JH7100 SoC and the Bare-metal boot examples. In order to run the examples presented in this guide, the following are required:
-
Ubuntu 18.04
-
VisionFive development board
¶ Revision History
|
Version |
Released |
Revision |
|
A |
2021-09-30 |
First release. |
¶ Boot Sources
The GPIO is used to select the boot vector and BootLoader source and offer multiple methods to obtain the BootLoader image.
The JH7100 SoC can boot from one of the sources listed in the following table, as selected by the PAD_GPIO [62:60] values.
Table - PAD_GPIO Values for Boot Source Selection
|
Processor |
SCFG_boot_mode |
PAD_GPIO [63] |
Boot Vector |
PAD_GPIO [62:60] |
|
U74 |
0x1 |
- |
SCFG_u74_reset_vector |
- |
|
0x0 (default) |
0x0 |
0x00_2000_0000, XIP Flash |
0x0: 1-bit quad SPI NOR flash memory 0x1: 4-bit quad SPI NOR flash memory 0x2: SDIO (Reserved) 0x3: eMMC (Reserved) 0x4: UART 0x5: USB (Reserved) 0x6: chiplink (Reserved) 0x7: SPI2AHB (Reserved) |
|
|
0x1 |
0x00_1840_0000, on-chip BootROM (32KB) |
|||
|
Notes: l The boot mode and boot source selection (PAD_GPIO [63]) can be read through syscon status registers. l Use the GPIO pad to select the vector and loader source by default. l PAD_GPIO [63] and PAD_GPIO [62:60] can be configured to 1 or 0 via pull-up/pull-down resister, button or jumper according to board hardware design. |
||||
Figure - Hardware Boot Sequence
¶ Boot Flow
The boot process starts when the processor is released from reset, and jumps to the reset vector address (0x1840,0000 by default), located in the BootROM address space.
The boot flow is a multi-stage process. Each stage is responsible for loading the next stage. The typical boot flow is illustrated in the following figure:
Figure - Typical Boot Flow
¶ BootROM
The BootROM is located in on-chip ROM, and the storage address is 0x1840,0000, which cannot be dynamically updated. After power-on, each HART jumps to 0x1800,0000 (located in RAM) by default and starts to execute BootROM.
The main function of the BootROM is to select the boot source and execute it. According to different hardware jumpers on the chip, only UART and QSPI sources are supported currently.
Table - Boot Source Description
|
Source |
Description |
|
UART |
Enter a simple command line. Load a limited size binary into the on-chip RAM and execute it. This mode is mainly used for firmware update. |
|
QSPI |
Automatically load the 32K Bootloader to 0x1800,0000 (located in RAM) from address 0 of NOR Flash and jump to it. |
Limitation: The file loaded from NOR Flash cannot exceed 32KB.
¶ BootLoader
The BootROM limits the size of data read from NOR Flash. The BootLoader reads DDRInit from 0x10000 in NOR Flash to 0x1808,0000 (located in RAM), and then jump to it for execution.
The DDRInit will initialize the DDR, then read fw_payload.bin (OpenSBI+Uboot, the file header contains file size information) from 0x40000 in NOR Flash to 0x8000,0000 (located in DDR), and then jump to it to execute the OpenSBI.
The normal output information is illustrated in the following figure:
Figure - Boot Loader Output Example
¶ OpenSBI
The binary of OpenSBI is packaged with the binary compiled by U-Boot in the way of payload to generate the final fw_payload.bin. The main functions of OpenSBI are:
-
Provide basic system calls for Linux
-
Switch the mode from M mode to S mode
-
Jump to 0x8002,0000 (located in DDR) to execute U-Boot.
The normal output information is illustrated in the following figure.
Figure - OpenSBI Output Example
¶ U-Boot
U-Boot runs at 0x8002,0000 and works in S mode. It contains basic file system and commonly used peripheral drivers (such as GMAC, UART, QSPI, USB, SDIO etc.). U-Boot can load the kernel image through ETH, UART, QSPI, SDIO or USB.
The following example describes how to load Linux 5.10 kernel image from SDIO.
Notes:
- The example assumes the installation of Ubuntu 18.04.
- Press Enter to confirm the operation or for the next command.
Steps:
-
SD card partition. The following is an example:
Figure - SD Card Partition Command Explanation -
Format the partition. The following is an example:
Figure - Format the Partition -
Generate image.fit from Freelight U SDK. Refer to the detailed guidelines in the link.
-
Copy the boot file. The following is an example:
Figure - Copying the Boot File -
Load the kernel (Linux 5.10 as an example).
Figure - Loading the Kernel
Notes:
The addresses 0x80200000, 0x86100000 and 0x86000000 have been specified when compiling and generating image.fit and cannot be modified.