在ARM中，事件发生将会触发中断，然而，中断并不会直接触发CPU，而是在由一个GIC，中断控制器来管理：
其中，中断分为
Supports three interrupt types:
Private Peripheral Interrupt (PPI）一个中断源对应一个CPU
Software Generated Interrupt (SGI) CPU对应CPU
Shared Peripheral Interrupt (SPI) 一个中断源对应多个CPU
今天的例子是用SGI中断来实现的，在处理中断的时候，主要分三步：
//step 1: cpu cpsr
CPU允许中断
20 __asm__ __volatile__(
21 "mrs r0, cpsr
"
22 "bic r0, r0, #0x80
"//设置CPSR的I位，将IRQ位打开
23 "msr cpsr, r0
"
24 ::: "r0"
25 );
26
27 //step 2: GIC
GIC
28 ICCICR_CPU0 = 1;//CPU接口控制寄存器
29 ICCPMR_CPU0 = 0xff;//中断优先标志寄存器
30 ICDDCR = 1;//设置本中断的开关
31 ICDIPR0_CPU0 = (0x00 << 0);//本中断的优先级
32 ICDIPTR0_CPU0 = 1;//选择指定的CPU
33 ICDISER0_CPU0 = (1 << 0);//设置本中断开启
34 各个寄存器描述如下：详细见4412 782页
35 //step 3: interrupt source
中断源
36 ICDSGIR = 0 | (1 << 16) | (0 << 24);//SGI控制寄存器CPUTargetList.TargetListFi lte
37 printf("welcome back!
");
下面是代码：
1 #include"regs.h" 2 3 int (*printf)(char *, ...) = 0xc3e114d8; 4 5 void init_ttb(unsigned long *addr); 6 void enable_mmu(void); 7 unsigned long data_abort_init(); 8 void memcopy(unsigned long* dest,unsigned long* source,int len); 9 void do_irq(); 10 11 int main() 12 { 13 *(unsigned long *)0x66000000 = do_irq; 14 unsigned long source_addr=data_abort_init(); 15 printf("swi_souce addr is %x ",source_addr); 16 memcopy(0x60000000,source_addr,0x1000); 17 enable_mmu(); 18 19 //step 1: cpu cpsr 20 __asm__ __volatile__( 21 "mrs r0, cpsr " 22 "bic r0, r0, #0x80 "//设置CPSR的I位，将IRQ位打开 23 "msr cpsr, r0 " 24 ::: "r0" 25 ); 26 27 //step 2: GIC 28 ICCICR_CPU0 = 1;//CPU接口控制寄存器 29 ICCPMR_CPU0 = 0xff;//中断优先标志寄存器 30 ICDDCR = 1;//设置本中断的开关 31 ICDIPR0_CPU0 = (0x00 << 0);//本中断的优先级 32 ICDIPTR0_CPU0 = 1;//选择指定的CPU 33 ICDISER0_CPU0 = (1 << 0);//设置本中断开启 34 35 //step 3: interrupt source 36 ICDSGIR = 0 | (1 << 16) | (0 << 24);//SGI控制寄存器CPUTargetList.TargetListFi lte 37 printf("welcome back! "); 38 } 39 40 void do_irq() 41 { 42 unsigned long data = ICCIAR_CPU0; 43 unsigned long irq_id = data & 0x3ff; 44 unsigned long cpu_id = (data >> 10) & 0x7; 45 ICCEOIR_CPU0 = irq_id | (cpu_id << 10); 46 printf("irq is %d, cpu is %d ", irq_id, cpu_id); 47 } 48 49 void memcopy(unsigned long* dest, unsigned long* source,int len) 50 { 51 int i=0;; 52 for(i=0;i<len;i++) 53 dest[i]=source[i]; 54 } 55 56 unsigned long data_abort_init() 57 { 58 unsigned long source; 59 __asm__ __volatile__( 60 "ldr %0, =voliate_start " 61 : "=r" (source) 62 ); 63 return source; 64 } 65 66 __asm__( 67 "voliate_start: " 68 //跳转目录 69 " b reset " 70 " b undefined " 71 " b swi " 72 " b pre_abt " 73 " b data_abt " 74 " .word 0 "//占位符号，一个位占4个字节 75 " b irq " 76 " b fiq " 77 " " 78 //跳转要分三部: 79 //1:将PC保存到新模式下的lr中； 80 //2:将CPSR保存在SPSR中 81 //3:初始化SP 82 //前两步由硬件完成，而第三部需要手动完成 83 "reset: " 84 85 "undefined: " 86 "mov sp, #0x66000000 "//初始化SP 87 "stmfd sp!, {r0-r12, lr} "//初始化sp，入栈保护寄存器 88 //打印一句话 89 "ldr r0, =und_string " 90 "ldr r2, show " 91 "blx r2 " 92 //跳回来分两部 93 //1:将CPSR保存在SPSR中 84 85 "undefined: " 86 "mov sp, #0x66000000 "//初始化SP 87 "stmfd sp!, {r0-r12, lr} "//初始化sp，入栈保护寄存器 88 //打印一句话 89 "ldr r0, =und_string " 90 "ldr r2, show " 91 "blx r2 " 92 //跳回来分两部 93 //1:将CPSR保存在SPSR中 94 //2:将PC保存到新模式下的lr中； 95 "mov sp, #0x66000000 "// 96 "ldmea sp, {r0-r12, pc}^ "// 97 98 "swi: " 99 100 "pre_abt: " 101 "data_abt: " 102 "sub lr, lr, #4 " 103 "mov sp, #0x66000000 "//初始化SP 104 "stmfd sp!, {r0-r12, lr} "//初始化sp，入栈保护寄存器 105 //打印一句话 106 "ldr r0, =data_string " 107 "ldr r2, show " 108 "blx r2 " 109 //跳回来分两部 110 //1:将CPSR保存在SPSR中 111 //2:将PC保存到新模式下的lr中； 112 "mov sp, #0x66000000 "// 113 "ldmea sp, {r0-r12, pc}^ "// 114 115 "irq: " 116 "sub lr, lr, #4 " 117 "mov sp, #0x66000000 "//初始化SP 118 "stmfd sp!, {r0-r12, lr} "//初始化sp，入栈保护寄存器 119 //打印一句话 120 "mov r2, #0x66000000 " 121 "ldr r1, [r2] " 122 "blx r1 " 123 124 // "ldr r0, =irq_string " 125 // "ldr r2, show " 126 // "blx r2 " 127 //跳回来分两部 128 //1:将CPSR保存在SPSR中 129 //2:将PC保存到新模式下的lr中； 130 "mov sp, #0x66000000 "// 131 "ldmea sp, {r0-r12, pc}^ "// 132 "fiq: " 133 "show: " 134 ".word 0xc3e114d8 " 135 136 "und_string: " 137 ".asciz "This is UND!\n" " 138 "data_string: " 139 ".asciz "This DATA_ABORT!\n" " 140 "irq_string: " 141 ".asciz "This IRQ!\n" " 142 143 ); 144 145 void init_ttb(unsigned long *addr) 146 { 147 unsigned long va = 0;//定义虚拟地址 148 unsigned long pa = 0;//定义物理地址 149 150 //40000000-------80000000 ==== 40000000------80000000 151 for(va=0x40000000; va<=0x80000000; va+=0x100000){ 152 pa = va; 153 addr[va >> 20] = pa | 2; 154 //|2的目的是将0-2位置为10此时将是小页模式4K 155 } 156 157 //00000000-------10000000 ==== 60000000------70000000 158 for(va=0x00000000; va<=0x10000000; va+=0x100000){ 159 pa = va+0x60000000; 160 addr[va >> 20] = pa | 2; 161 } 162 163 //10000000-------14000000 ==== 10000000------14000000 164 for(va=0x10000000; va<=0x14000000; va+=0x100000){ 165 pa = va; 166 addr[va >> 20] = pa | 2; 167 } 168 169 //30000000-------40000000 ==== 50000000------60000000 170 for(va=0x30000000; va<0x40000000; va+=0x100000){ 171 pa = va + 0x20000000; 172 addr[va >> 20] = pa | 2; 173 } 174 } 175 176 void enable_mmu(void) 177 178 { 179 unsigned long addr = 0x70000000; 180 init_ttb(addr); 181 //step:初始化页表 182 183 unsigned long mmu = 1 | (1 << 1) | (1 << 8); 184 //将MMU的第0,1,8位置1 185 __asm__ __volatile__( 186 "mov r0, #3 " 187 "MCR p15, 0, r0, c3, c0, 0 "//manager 188 "MCR p15, 0, %0, c2, c0, 0 "//addr 189 "MCR p15, 0, %1, c1, c0, 0 "// enable mmu 190 : 191 : "r" (addr), "r" (mmu) 192 : "r0" 193 ); 194 printf("MMU is enable! "); 195 } 196
在代码中，主函数其他的部分在前面都已经说了，已不再说。主要是在VICTOR函数中，将处理中断的部分，做成了一个函数，以后更容易修改处理的部分。
void do_irq()
41 {
42 unsigned long data = ICCIAR_CPU0;//取出IRQ ID 和CPU ID
43 unsigned long irq_id = data & 0x3ff;
44 unsigned long cpu_id = (data >> 10) & 0x7;
45 ICCEOIR_CPU0 = irq_id | (cpu_id << 10);//清除CPU
46 printf("irq is %d, cpu is %d
", irq_id, cpu_id);
47 }
//总的来说，在以前的基础上面，今天主要认识了GIC的配置，更重要的是，中断分为四步：
1，CPU开
2，GIC配置
3，中断源
4，处理中断，清中断