Android源码编译（三）----------->beagleboard-xm u-boot

1, Build

Fromhttp://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 referencehttp://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 0×80008000. 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=0×80008000 -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: typedefstructglobal_data {

 2: bd_t*bd;

 3: unsigned longflags;

 4: unsigned longbaudrate;

 5: unsigned longhave_console;/* serial_init() was called */

 6: unsigned longenv_addr;/* Addressof Environment struct */

 7: unsigned longenv_valid;/* Checksum of Environment valid? */

 8: unsigned longfb_base;/* base address of frame buffer */

 9: #ifdef CONFIG_VFD

10: unsigned charvfd_type;/* display type */

11: #endif

12: #ifdef CONFIG_FSL_ESDHC

13: unsigned longsdhc_clk;

14: #endif

15: #ifdef CONFIG_AT91FAMILY

16: /* "static data" needed by at91's clock.c */

17: unsigned longcpu_clk_rate_hz;

18: unsigned longmain_clk_rate_hz;

19: unsigned longmck_rate_hz;

20: unsigned longplla_rate_hz;

21: unsigned longpllb_rate_hz;

22: unsigned longat91_pllb_usb_init;

23: #endif

24: #ifdef CONFIG_ARM

25: /* "static data" needed by most of timer.c on ARM platforms */

26: unsigned longtimer_rate_hz;

27: unsigned longtbl;

28: unsigned longtbu;

29: unsigned long longtimer_reset_value;

30: unsigned longlastinc;

31: #endif

32: unsigned longrelocaddr;/* Start address of U-Boot in RAM */

33: phys_size_tram_size;/* RAM size */

34: unsigned longmon_len;/* monitor len */

35: unsigned longirq_sp;/* irq stack pointer */

36: unsigned longstart_addr_sp;/* start_addr_stackpointer */

37: unsigned longreloc_off;

38: #if !(defined(CONFIG_SYS_NO_ICACHE) && defined(CONFIG_SYS_NO_DCACHE))

39: unsigned longtlb_addr;

40: #endif

41: void**jt;/* jump table */

42: charenv_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: #

 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

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

0×80008000reset vector

0×8007020 ~0×80008028interrupt vectors

0×8000100 : Linux boot parameters

SDRAM #1

0x4020FF80 ~ 0×40210000global_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: mrsr0, cpsr

 2: bicr0, r0, #0x1f

 3: orrr0, r0, #0xd3

 4: msrcpsr,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_ADDR0x4020f800

 2: #define CONFIG_SYS_INIT_RAM_SIZE0x800

 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 0×49032000

Initialize environment, because no NAND, so the environment is relocated to RAM as in arch\arm\include\asm\global_data.h

 1: #defineGD_FLG_RELOC0x00001/* 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 0×49020000, datasheet athttp://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 0×80000000
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 0×80000100
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 …