3.16 基于OHCI的USB主机 —— 中断向量处理

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使用芯片提供的例程，中断向量处理程序也非常简单。在上面的AIC中断配置中，中断产生不是直接调用用于处理中断事务的函数，而是调用一个用汇编语言编写的函数，该函数主要功能是在中断处理函数调用前后，完成寄存器现场的保护和恢复。
这部分代码实际上与OHCI没有关系，是属于CPU的处理，不同的CPU其中断向量处理是不一样的。所以这里的代码仅作参考而已。

;------------------------------------------------------------------------------ ;- ATMEL Microcontroller Software Support - ROUSSET - ;------------------------------------------------------------------------------ ; The software is delivered "AS IS" without warranty or condition of any ; kind, either express, implied or statutory. This includes without ; limitation any warranty or condition with respect to merchantability or ; fitness for any particular purpose, or against the infringements of ; intellectual property rights of others. ;----------------------------------------------------------------------------- ;- File source : arm_isr.s ;- Object : Example of IT handler calling a C function ;- Compilation flag : None ;- ;- 1.0 26/11/02 FB : Creation ARM ADS ;------------------------------------------------------------------------------ AREA itHandler, CODE, READONLY ;------------------------------------------------------------------------------ ;- LISR vector handler for system peripherals ;-------------------------------------------- ;- This macro save the context, call the LISR dispatch routine, and restore ;- the context ;------------------------------------------------------------------------------ INCLUDE AT91RM9200.inc ;-------------------------------- ;- ARM Core Mode and Status Bits ;-------------------------------- ARM_MODE_USER EQU 0x10 ARM_MODE_FIQ EQU 0x11 ARM_MODE_IRQ EQU 0x12 ARM_MODE_SVC EQU 0x13 ARM_MODE_ABORT EQU 0x17 ARM_MODE_UNDEF EQU 0x1B ARM_MODE_SYS EQU 0x1F I_BIT EQU 0x80 F_BIT EQU 0x40 T_BIT EQU 0x20 ;------------------------------------------------------------------------------ ;- IRQ Entry ;----------- ;------------------------------------------------------------------------------ MACRO IRQ_ENTRY $reg ;- Adjust and save LR_irq in IRQ stack sub r14, r14, #4 stmfd sp!, {r14} ;- Write in the IVR to support Protect Mode ;- No effect in Normal Mode ;- De-assert the NIRQ and clear the source in Protect Mode ldr r14, =AT91C_BASE_AIC str r14, [r14, #AIC_IVR] ;- Save SPSR and r0 in IRQ stack mrs r14, SPSR stmfd sp!, {r0, r14} ;- Enable Interrupt and Switch in SYS Mode mrs r0, CPSR bic r0, r0, #I_BIT orr r0, r0, #ARM_MODE_SYS msr CPSR_c, r0 ;- Save scratch/used registers and LR in User Stack IF "$reg" = "" stmfd sp!, { r1-r3, r12, r14} ELSE stmfd sp!, { r1-r3, $reg, r12, r14} ENDIF MEND ;------------------------------------------------------------------------------ ;- IRQ Exit ; --------- ;------------------------------------------------------------------------------ MACRO IRQ_EXIT $reg ;- Restore scratch/used registers and LR from User Stack IF "$reg" = "" ldmia sp!, { r1-r3, r12, r14} ELSE ldmia sp!, { r1-r3, $reg, r12, r14} ENDIF ;- Disable Interrupt and switch back in IRQ mode mrs r0, CPSR bic r0, r0, #ARM_MODE_SYS orr r0, r0, #I_BIT:OR:ARM_MODE_IRQ msr CPSR_c, r0 ;- Mark the End of Interrupt on the AIC ldr r0, =AT91C_BASE_AIC str r0, [r0, #AIC_EOICR] ;- Restore SPSR_irq and r0 from IRQ stack ldmia sp!, {r0, r14} msr SPSR_cxsf, r14 ;- Restore adjusted LR_irq from IRQ stack directly in the PC ldmia sp!, {pc}^ MEND ;------------------------------------------------------------------------------ ; AT91F_ASM_UHP_Handler ; --------------------- ; Handler called by the AIC ; ; Save context ; Call C handler ; Restore context ;------------------------------------------------------------------------------ EXPORT AT91F_ASM_UHP_Handler IMPORT AT91F_UHP_Handler AT91F_ASM_UHP_Handler IRQ_ENTRY ldr r1, =AT91F_UHP_Handler mov r14, pc bx r1 IRQ_EXIT END