第一次接触Tricore, 学习下从芯片上电到运行到main函数的过程，本文以TC36X为例，具体可参考英飞凌官方的Infineon-AURIX_TC3xx_Part1-UserManual-v02_00-EN
首先Tricore类似三星的MPU，有一段自带的BROM，这段FLASH中存储了一段固化的启动代码，称为Startup Sofrware(SSW), 这个意味着这段代码是英飞凌出厂就烧进去的，且无法覆盖。
然后SSW什么时候执行呢?当然是RESET的时候，英飞凌把RESET分为三种:
#if defined(__HIGHTEC__)
#pragma section
#pragma section ".bmhd_0_orig" a
#endif
#if defined(__TASKING__)
#pragma section farrom "bmhd_0_orig"
#endif
#if defined(__DCC__)
#pragma section CONST ".bmhd_0_orig" far-absolute R
#endif
#if defined(__ghs__)
#pragma ghs section rodata= ".bmhd_0_orig"
#endif
const Ifx_Ssw_Bmhd bmhd_0_orig =
{
0x003E, /* 0x000: .bmi: Boot Mode Index (BMI) PINDIS */
0xB359, /* 0x002: .bmhdid: Boot Mode Header ID (CODE) = B359H */
0xA0000000, /* 0x004: .stad: User Code start address */
0xD86CBDAB, /* 0x008: .crc: Check Result for the BMI Header (offset 000H - 007H) */
0x27934254, /* 0x00C: .crcInv: Inverted Check Result for the BMI Header (offset 000H - 007H) */
{
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x010: Reserved (0x010 - 0x01F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x020: Reserved (0x020 - 0x02F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x030: Reserved (0x030 - 0x03F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x040: Reserved (0x040 - 0x04F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x050: Reserved (0x050 - 0x05F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x060: Reserved (0x060 - 0x06F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x070: Reserved (0x070 - 0x07F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x080: Reserved (0x080 - 0x08F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x090: Reserved (0x090 - 0x09F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x0A0: Reserved (0x0A0 - 0x0AF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x0B0: Reserved (0x0B0 - 0x0BF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x0C0: Reserved (0x0C0 - 0x0CF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x0D0: Reserved (0x0D0 - 0x0DF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x0E0: Reserved (0x0E0 - 0x0EF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000 /* 0x0F0: Reserved (0x0F0 - 0x0FF) */
},
{
0x00000000, /* 0x100: .pw0: Password protection word 0 (lsw) */
0x00000000, /* 0x104: .pw1: Password protection word 1 */
0x00000000, /* 0x108: .pw2: Password protection word 2 */
0x00000000, /* 0x10C: .pw3: Password protection word 3 */
0x00000000, /* 0x110: .pw4: Password protection word 4 */
0x00000000, /* 0x114: .pw5: Password protection word 5 */
0x00000000, /* 0x118: .pw6: Password protection word 6 */
0x00000000, /* 0x11C: .pw7: Password protection word 7 (msw) */
},
{
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x120: Reserved (0x120 - 0x12F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x130: Reserved (0x130 - 0x13F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x140: Reserved (0x140 - 0x14F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x150: Reserved (0x150 - 0x15F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x160: Reserved (0x160 - 0x16F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x170: Reserved (0x170 - 0x17F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x180: Reserved (0x180 - 0x18F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x190: Reserved (0x190 - 0x19F) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x1A0: Reserved (0x1A0 - 0x1AF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x1B0: Reserved (0x1B0 - 0x1BF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x1C0: Reserved (0x1C0 - 0x1CF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000, /* 0x1D0: Reserved (0x1D0 - 0x1DF) */
0x00000000, 0x00000000, 0x00000000, 0x00000000 /* 0x1E0: Reserved (0x1E0 - 0x1EF) */
},
0x43211234 /* 0x1F0: .confirmation: 32-bit CODE, (always same) */
};
这里的BMI =0x3E =0b111110 ，大家可以具体看看这种配置是社么意思
比如PINDIS=0且 HWCFGbits [3:1] = 0b111 代表上电无需检测外部Pin14.2等引脚电平，直接start from Flash，那么从Flash哪个地址开始执行呢?
BMHD.STAD: User Code start address 是可以配置的
这里配置为了0xA0000000
这是NON-CACHE CPU0的Program Flash起始地址
#if defined(__HIGHTEC__)
#pragma section
#pragma section ".start" x
#endif
void _START(void)
{
Ifx_Ssw_jumpToFunction(__StartUpSoftware);
}
#if defined(__HIGHTEC__)
#pragma section
#endif
通过宏将void _START(void)代码放到了section .start
链接脚本
#define LCF_STARTPTR_NC_CPU0 0xA0000000
group (ordered)
{
group reset (run_addr=RESET)
{
section "reset" ( size = 0x20, fill = 0x0800, attributes = r )
{
select ".text.start";
}
}
group interface_const (run_addr=mem:pfls0[0x0020])
{
select "*.interface_const";
}
"__IF_CONST" := addressof(group:interface_const);
"__START0" := LCF_STARTPTR_NC_CPU0;
"__START1" := LCF_STARTPTR_NC_CPU1;
}
总之就是将_START放到了CPU0的PFLASH0的起始地址，也就是BMHD中指定的STAD，而CPU1的_START1同样也放到了PFLASH1的起始地址，顺便提一下，上电的时候CPU0是默认开启的，且SSW也是由这个核执行的，其他所有CPU都处于HALT状态。
到这里SSW就结束了，后面就是执行用户写的代码，第一个指令就是_START(相当于CPU0的启动代码)位于Ifx_Ssw_Tc0.c
void _START(void)
{
Ifx_Ssw_jumpToFunction(__StartUpSoftware);
}/*汇编直接跳转到__StartUpSoftware*/
static void __StartUpSoftware(void)
{
/* Initialize A1 pointer to use the global constants with small data addressing */
Ifx_Ssw_setAddressReg(a1, __SDATA2(0));
/* Set the PSW to its reset value in case of a warm start,clear PSW.IS */
Ifx_Ssw_MTCR(CPU_PSW, IFX_CFG_SSW_PSW_DEFAULT);
/* This phase is executed only if last reset is not of type application reset */
if (Ifx_Ssw_isApplicationReset() != 1)
{
Ifx_Ssw_jumpToFunction(__StartUpSoftware_Phase2);
}
else
{
Ifx_Ssw_jumpToFunction(__StartUpSoftware_Phase3ApplicationResetPath);
}
}
/*System Reset*/
static void __StartUpSoftware_Phase3ApplicationResetPath(void)
{
IFX_SSW_INIT_CONTEXT();
Ifx_Ssw_jumpToFunction(__StartUpSoftware_Phase5);
}
#define IFX_SSW_INIT_CONTEXT() \
{ \
/* Load user stack pointer */ \
Ifx_Ssw_setAddressReg(a10, __USTACK(0)); \
Ifx_Ssw_DSYNC(); \
\
/*Initialize the context save area for CPU0. Function Calls Possible */ \
/* Setup the context save area linked list */ \
Ifx_Ssw_initCSA((unsigned int *)__CSA(0), (unsigned int *)__CSA_END(0)); \
/* Clears any instruction buffer */ \
Ifx_Ssw_ISYNC(); \
}/*初始化CPU0 的RAM, 其他核也有自己的专用RAM，参考手册MemoryMap
包括CSA 将utack 栈顶赋值给寄存器A10(相当于ARM 的LDR SP ,= StackTopAddr) CPU的RAM
怎么分配的可以参考链接脚本*/
按道理说只有初始化的Stack才能执行C语言写的函数，
那么在这之前的那些步骤难道不算C语言函数?
static void __StartUpSoftware_Phase5(void)
{
/* SMU alarm handling */
IFX_CFG_SSW_CALLOUT_SMU();
Ifx_Ssw_jumpToFunction(__StartUpSoftware_Phase6);
}/*其实是直接跳转到phase6*/
static void __StartUpSoftware_Phase6(void)
{
/* Start remaining cores as a daisy-chain */
#if (IFX_CFG_SSW_ENABLE_TRICORE1 != 0)
Ifx_Ssw_startCore(&MODULE_CPU1, (unsigned int)__START(1)); /*The status returned by function call is ignored */
#endif /* #if (IFX_CFG_CPU_CSTART_ENABLE_TRICORE1 != 0)*/
Ifx_Ssw_jumpToFunction(__Core0_start);
}/*可以看到CPU1其实是由CPU0启动的，当然你要配置使用CPU1*/
Ifx_Ssw_startCore(&MODULE_CPU1, (unsigned int)__START(1));
void Ifx_Ssw_startCore(Ifx_CPU *cpu, unsigned int programCounter)
{
/* Set the PC */
cpu->PC.B.PC = (unsigned int)programCounter >> 1U;
/* release boot halt mode if required */
Ifx_CPU_SYSCON syscon;
syscon = cpu->SYSCON;
if (syscon.B.BHALT)
{
syscon.B.BHALT = 0U;
cpu->SYSCON = syscon;
}
}
可以看到是直接将cpu1->PC寄存器指向_START1()函数，
并且通过设置某个特殊寄存器，解除CPU1的HALT状态，使其进入RUN，
那么CPU1就可以执行_START1()了
CPU0开启CPU1后，继续自己的初始化
Ifx_Ssw_jumpToFunction(__Core0_start);
static void __Core0_start(void)
{
... 很多代码大家可以自己去看, 这里就不分析了,
值得注意的是初始化看门狗, 初始化RAM,
建立异常和中断Vector,
中断栈, 使能或不使能Cache等等
/*Call main function of Cpu0 */
Ifx_Ssw_jumpToFunction(core0_main);
}
最重要的是Ifx_Ssw_jumpToFunction(core0_main) 这样芯片从上电CPU0 RUN CPUX HALT ->读取UFLASH-UCB-BMHD->_START0->core_start(cpu1)->go to MAIN函数就完成了， 同样的CPU1执行_START1() 后也会继续执行自己的core1_main
现在多核CPU就可以各自执行自己的MAIN函数(它们在不同的flash地址), 各玩各的，但这样是显然不行的，涉及到共享资源访问，核间通信等问题以后再研究。