beagleboard-xm research(2)–u-boot
2011/02/24 留下评论
1, Build
From http://code.google.com/p/beagleboard/wiki/BeagleSourceCode, download u-boot 1.3.3 for beagleboard
If you uses latest ARM gcc from codesourcery, you maybe get following error
arm-none-linux-gnueabi-gcc -g -Os -fno-strict-aliasing -fno-common -ffixed-r8 -msoft-float -D__KERNEL__ -DTEXT_BASE=0x80e80000 -I/home/ken/bb/u-boot/u-boot-beagle/include -fno-builtin -ffreestanding -nostdinc -isystem /opt/sourcery_g++/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.3/include -pipe -DCONFIG_ARM -D__ARM__ -march=armv7a -Wall -Wstrict-prototypes -c -o hello_world.o hello_world.c
hello_world.c:1: error: bad value (armv7a) for -march= switch
This issue is caused by latest GCC changing for ARMV7-A architecture, that should uses -march=armv7-a but not -march=armv7a.
To fix it, in u-boot\cpu\omap3\config.mk, change following line:
PLATFORM_CPPFLAGS += -march=armv7a
To:
PLATFORM_CPPFLAGS += -march=armv7-a
Although success to build uboot.bin image, but beagleboard-xm fail to boot it:
a) the serial baudrate is changed from 115200 to 57600
b) system hang after find no NAND memory.
But the u-boot image built from git mainline git://git.denx.de/u-boot.git with omap3 patch can work correctly, please reference http://www.elinux.org/BeagleBoard
1: git clone git://git.denx.de/u-boot.git u-boot-main
2: cd u-boot-main
3: git checkout --track -b omap3 origin/master
Build
1: make CROSS_COMPILE=arm-none-linux-gnueabi- mrproper
2: make CROSS_COMPILE=arm-none-linux-gnueabi- omap3_beagle_config
3: make CROSS_COMPILE=arm-none-linux-gnueabi-
As mentioned by previous discussion, u-boot.bin is loaded into the first of internal SDRAM at address 0x80008000. So in uboot\board\ti\beagle\config.mk:
1: #
2: # Physical Address:
3: # 8000'0000 (bank0)
4: # A000/0000 (bank1)
5: # Linux-Kernel is expected to be at 8000'8000, entry 8000'8000
6: # (mem base + reserved)
7:
8: # For use with external or internal boots.
9: CONFIG_SYS_TEXT_BASE = 0x80008000
CONFIG_SYS_TEXT_BASE as macro passed into build options as:
arm-none-linux-gnueabi-gcc -D__ASSEMBLY__ -g -Os -fno-common -ffixed-r8 -msoft-float -D__KERNEL__ -DCONFIG_SYS_TEXT_BASE=0x80008000 -I/home/ken/bb/u-boot/u-boot-mailine/include -fno-builtin -ffreestanding -nostdinc -isystem /opt/sourcery_g++/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.3/include -pipe -DCONFIG_ARM -D__ARM__ -marm -mabi=aapcs-linux -mno-thumb-interwork -march=armv5 -o start.o start.S –c
(BTW: there is some interesting compiler options used: –ffreestanding, –isystem, –mabi=aapcs-linux)
It is worth to mention that uboot will keep some information into a global_data in top of stack, the structure is defined in uboot\arch\arm\include\asm\global_data.h:
1: typedef struct global_data {
2: bd_t *bd;
3: unsigned long flags;
4: unsigned long baudrate;
5: unsigned long have_console; /* serial_init() was called */
6: unsigned long env_addr; /* Address of Environment struct */
7: unsigned long env_valid; /* Checksum of Environment valid? */
8: unsigned long fb_base; /* base address of frame buffer */
9: #ifdef CONFIG_VFD
10: unsigned char vfd_type; /* display type */
11: #endif
12: #ifdef CONFIG_FSL_ESDHC
13: unsigned long sdhc_clk;
14: #endif
15: #ifdef CONFIG_AT91FAMILY
16: /* "static data" needed by at91's clock.c */
17: unsigned long cpu_clk_rate_hz;
18: unsigned long main_clk_rate_hz;
19: unsigned long mck_rate_hz;
20: unsigned long plla_rate_hz;
21: unsigned long pllb_rate_hz;
22: unsigned long at91_pllb_usb_init;
23: #endif
24: #ifdef CONFIG_ARM
25: /* "static data" needed by most of timer.c on ARM platforms */
26: unsigned long timer_rate_hz;
27: unsigned long tbl;
28: unsigned long tbu;
29: unsigned long long timer_reset_value;
30: unsigned long lastinc;
31: #endif
32: unsigned long relocaddr; /* Start address of U-Boot in RAM */
33: phys_size_t ram_size; /* RAM size */
34: unsigned long mon_len; /* monitor len */
35: unsigned long irq_sp; /* irq stack pointer */
36: unsigned long start_addr_sp; /* start_addr_stackpointer */
37: unsigned long reloc_off;
38: #if !(defined(CONFIG_SYS_NO_ICACHE) && defined(CONFIG_SYS_NO_DCACHE))
39: unsigned long tlb_addr;
40: #endif
41: void **jt; /* jump table */
42: char env_buf[32]; /* buffer for getenv() before reloc. */
43: } gd_t;
The structure size maybe different according to configure macros, so at beginning of build, a script is used to calculate current size of global data:
1: arm-none-linux-gnueabi-gcc -DDO_DEPS_ONLY \
2: -g -Os -fno-common -ffixed-r8 -msoft-float -D__KERNEL__ -DCONFIG_SYS_TEXT_BASE=0x80008000 -I/home/ken/bb/u-boot/u-boot-mailine/include -fno-builtin -ffreestanding -nostdinc -isystem /opt/sourcery_g++/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.3/include -pipe -DCONFIG_ARM -D__ARM__ -marm -mabi=aapcs-linux -mno-thumb-interwork -march=armv5 -Wall -Wstrict-prototypes -fno-stack-protector \
3: -o lib/asm-offsets.s lib/asm-offsets.c -c -S
4: Generating include/generated/generic-asm-offsets.h
5: tools/scripts/make-asm-offsets lib/asm-offsets.s include/generated/generic-asm-offsets.h
In EFI, there is similar design that put PeiCore’s private data at top of stack as global data.
2, Memory Map
0x9fff0000 ~ TLB table
0x9ff7f000 ~ 0x9fff0000 : Reserved for U-boot (449K)
0x9ff1f000 ~ 0x9ff7f000: for malloc(384k)
0x9ff1efe0 ~ 0x9ff1f000: board info (32 bytes)
0x9ff1ef68 ~ 0x9ff1efe0: global data (120 bytes)
0x9ff1ef68: New stack point
0x80008000 reset vector
0x8007020 ~0x80008028 interrupt vectors
0x8000100 : Linux boot parameters
SDRAM #1
0x4020FF80 ~ 0x40210000 global_data
0x4020F800 ~0x4020FF80 stack
2, Workflow
- uboot\arch\cpu\armv7\start.S
- Like x-load, start.S provide the first assemble loader for u-boot
- The first instruction is reset vector and the interrupt/exception handle are closed to it. As system.map file:
80008000 T _start
80008020 t _undefined_instruction
80008024 t _software_interrupt
80008028 t _prefetch_abort
8000802c t _data_abort
80008030 t _not_used
80008034 t _irq
80008038 t _fiq
- Switch CPU to SVC32 mode.
1: mrs r0, cpsr
2: bic r0, r0, #0x1f
3: orr r0, r0, #0xd3
4: msr cpsr,r0
- Copy interrupt vectors to ROM indirect address: 0x4020F800
- Because beagleboard-xm does not have NAND/OneNand device, so need copy DPLL initialize code into ROM indirect address after interrupt vectors
- Init CPU in assemble like x-load:
- Setup important registers: mmu, cache
- Setup memory timing.
- Setup stack for C code at 0x4020FF80 (uboot\include\configs\omap3_beagle.h):
1: #define CONFIG_SYS_INIT_RAM_ADDR 0x4020f800
2: #define CONFIG_SYS_INIT_RAM_SIZE 0x800
3: #define CONFIG_SYS_INIT_SP_ADDR (CONFIG_SYS_INIT_RAM_ADDR + \
4: CONFIG_SYS_INIT_RAM_SIZE - \
5: GENERATED_GBL_DATA_SIZE)
As above mentioned, before top of stack, global_data will be stored, the size of global_data is determined/generated at build time (include\generated\generic-asm-offices.h)
1: #define GENERATED_GBL_DATA_SIZE (128) /* (sizeof(struct global_data) + 15) & ~15 */
- Call C function board_init_f (uboot\arch\arm\lib\board.c):
- Assign/Init global data structure at 0x4020F800
- Disable memory I/O cache for compiler optization, just like MemoryFence() used in edk2 MdePkg:
1: __asm__ __volatile__("": : :"memory");
Because many hardware intialization or I/O accessing will use write/read same MMIO address, the compiler maybe optimizate these code out or re-arrange read/write sequence, so it will break. Above instruction like asm volatitle used.
- call all function defined in init_sequence array:
- timer_init (arch/arm/cpu/armv7/omap-common/timer.c)
- here used GPTIMER2 (there are 12 GP time in OMAP3), which base adress is 0x49032000
- Initialize environment, because no NAND, so the environment is relocated to RAM as in arch\arm\include\asm\global_data.h
- timer_init (arch/arm/cpu/armv7/omap-common/timer.c)
1: #define GD_FLG_RELOC 0x00001 /* Code was relocated to RAM */
By default, some configuration value comes from global variable default_environment in common\env_common.c such as baudrate.
- serial initliazation
beagleboard-xm use NS16650 serial at COM3 0x49020000, datasheet at http://www.national.com/ds/PC/PC16550D.pdf
- Init stage1 console for print
- Print CPU/board information
- Init I2C device.
- Init SDRAM device, caculate the bank’s size.
- Reserve RAM memory for u-boot at top of RAM1 started from 0x80000000
- Relocate code for new location at 0x9ff7f000/stack at 0x9ff1ef60 (arch\arm\cpu\armv7\start.S, relocate_code())
- Jump to board_init_r() in new location in RAM, (The sequence is very like PeiCore relocation in EFI)
- In beaglboard’s board_init_r() (board\ti\beagle\beagle.c):
- Init GPMC
- set board id for linux as 1546
- set boot parameter address at 0x80000100
- Init MMC driver
- Init stdio drivers such as serial, nulldev
- Init jumptable?
- Evalute board version, for beagleboard-xm board, set VAUX2 to 1.8v for EHCI PHY. And print DIE ID at 0x4830A200
- Init IRQ/FIQ stack which size are all 4K
- Change CPSR to enable interrupt
- Enter main_loop() function to read boot/user script …
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