目录
title: 字符设备驱动(三)中断框架
tags: linux
date: 2018-11-22 18:58:22
toc: true
---
字符设备驱动(三)中断框架
引入
裸机中断流程
- 外部触发
- CPU 发生中断, 强制的跳到异常向量处
- 跳转到具体函数
- 保存被中断处的现场（各种寄存器的值）。
- 处理具体任务
- 恢复被中断的现场
LINUX流程
ARM 架构的 CPU 的异常向量基址可以是 0x0000 0000,也可以是 0xffff0000，这个地址并不代表实际的内存，是虚拟地址.当建立了虚拟地址与物理地址间的映射后，得将那些异常向量，即相当于把那些跳转指令复制拷贝到这个 0xffff0000 这个地址处去。
汇编处理
在trap_init中实现(start_kernel中调用)
// arch/arm/kernel/traps.c
void __init trap_init(void)
{
unsigned long vectors = CONFIG_VECTORS_BASE;
extern char __stubs_start[], __stubs_end[];
extern char __vectors_start[], __vectors_end[];
extern char __kuser_helper_start[], __kuser_helper_end[];
int kuser_sz = __kuser_helper_end - __kuser_helper_start;
/*
* Copy the vectors, stubs and kuser helpers (in entry-armv.S)
* into the vector page, mapped at 0xffff0000, and ensure these
* are visible to the instruction stream.
*/
memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);
memcpy((void *)vectors + 0x200, __stubs_start, __stubs_end - __stubs_start);
memcpy((void *)vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);
/*
* Copy signal return handlers into the vector page, and
* set sigreturn to be a pointer to these.
*/
memcpy((void *)KERN_SIGRETURN_CODE, sigreturn_codes,
sizeof(sigreturn_codes));
flush_icache_range(vectors, vectors + PAGE_SIZE);
modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
}
拷贝向量表
memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);
vectors=CONFIG_VECTORS_BASE,是配置项,,在最开始的内核配置.config中定义为0xffff0000__vectors_start在arch/arm/kernel/entry-armv.S中定义,是一段跳转指令,很明显是中断跳转指令
.globl __vectors_start
__vectors_start:
swi SYS_ERROR0
b vector_und + stubs_offset
ldr pc, .LCvswi + stubs_offset
b vector_pabt + stubs_offset
b vector_dabt + stubs_offset
b vector_addrexcptn + stubs_offset
b vector_irq + stubs_offset
b vector_fiq + stubs_offset
.globl __vectors_end
__vectors_end:
向量表宏解析
其中的vector_und等都是一个宏,搜索代码是搜索不到的.本质就是保护现场,设置管理模式,然后跳转
.macro vector_stub, name, mode, correction=0
.align 5
vector_\name:
.if \correction
sub lr, lr, #\correction
.endif
@
@ Save r0, lr_<exception> (parent PC) and spsr_<exception>
@ (parent CPSR)
@
stmia sp, {r0, lr} @ save r0, lr
mrs lr, spsr
str lr, [sp, #8] @ save spsr
@
@ Prepare for SVC32 mode. IRQs remain disabled.
@
mrs r0, cpsr
eor r0, r0, #(\mode ^ SVC_MODE)
msr spsr_cxsf, r0
@
@ the branch table must immediately follow this code
@
and lr, lr, #0x0f
mov r0, sp
ldr lr, [pc, lr, lsl #2]
movs pc, lr @ branch to handler in SVC mode
.endm
尝试展开这个宏
vector_stub und, UND_MODE
.long __und_usr @ 0 (USR_26 / USR_32)
.long __und_invalid @ 1 (FIQ_26 / FIQ_32)
.long __und_invalid @ 2 (IRQ_26 / IRQ_32)
.long __und_svc @ 3 (SVC_26 / SVC_32)
.long __und_invalid @ 4
.long __und_invalid @ 5
.long __und_invalid @ 6
.long __und_invalid @ 7
.long __und_invalid @ 8
.long __und_invalid @ 9
.long __und_invalid @ a
.long __und_invalid @ b
.long __und_invalid @ c
.long __und_invalid @ d
.long __und_invalid @ e
.long __und_invalid @ f
.align 5
展开如下:
vector_und:
@
@ Save r0, lr_<exception> (parent PC) and spsr_<exception>
@ (parent CPSR)
@
stmia sp, {r0, lr} @ save r0, lr
mrs lr, spsr
str lr, [sp, #8] @ save spsr
@
@ Prepare for SVC32 mode. IRQs remain disabled.
@
mrs r0, cpsr
eor r0, r0, #(\mode ^ SVC_MODE)
msr spsr_cxsf, r0
@
@ the branch table must immediately follow this code
@
and lr, lr, #0x0f
mov r0, sp
ldr lr, [pc, lr, lsl #2]
movs pc, lr @ branch to handler in SVC mode
.long __und_usr @ 0 (USR_26 / USR_32)
.long __und_invalid @ 1 (FIQ_26 / FIQ_32)
.long __und_invalid @ 2 (IRQ_26 / IRQ_32)
.long __und_svc @ 3 (SVC_26 / SVC_32)
.long __und_invalid @ 4
.long __und_invalid @ 5
.long __und_invalid @ 6
.long __und_invalid @ 7
.long __und_invalid @ 8
.long __und_invalid @ 9
.long __und_invalid @ a
.long __und_invalid @ b
.long __und_invalid @ c
.long __und_invalid @ d
.long __und_invalid @ e
.long __und_invalid @ f
.align 5
展开下中断跳转的宏vector_irq,这里比未定义指令异常增加了先计算lr返回地址lr=lr-4
# vector_stub irq, IRQ_MODE, 4
# correction=4
vector_irq:
@.if \correction
@sub lr, lr, #\correction
@.endif
if #4
sub lr,lr,#4
endif
@
@ Save r0, lr_<exception> (parent PC) and spsr_<exception>
@ (parent CPSR)
@
stmia sp, {r0, lr} @ save r0, lr
mrs lr, spsr
str lr, [sp, #8] @ save spsr
@
@ Prepare for SVC32 mode. IRQs remain disabled.
@
mrs r0, cpsr
eor r0, r0, #(\mode ^ SVC_MODE)
msr spsr_cxsf, r0
@
@ the branch table must immediately follow this code
@
and lr, lr, #0x0f
mov r0, sp
ldr lr, [pc, lr, lsl #2]
movs pc, lr @ branch to handler in SVC mode
# 跳转地址
.long __irq_usr @ 0 (USR_26 / USR_32)
.long __irq_invalid @ 1 (FIQ_26 / FIQ_32)
.long __irq_invalid @ 2 (IRQ_26 / IRQ_32)
.long __irq_svc @ 3 (SVC_26 / SVC_32)
.long __irq_invalid @ 4
.long __irq_invalid @ 5
.long __irq_invalid @ 6
.long __irq_invalid @ 7
.long __irq_invalid @ 8
.long __irq_invalid @ 9
.long __irq_invalid @ a
.long __irq_invalid @ b
.long __irq_invalid @ c
.long __irq_invalid @ d
.long __irq_invalid @ e
.long __irq_invalid @ f
跳转函数
宏的最后都有一个跳转,比如中段函数跳转到__irq_usr
__irq_usr:
usr_entry
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
get_thread_info tsk
#ifdef CONFIG_PREEMPT
ldr r8, [tsk, #TI_PREEMPT] @ get preempt count
add r7, r8, #1 @ increment it
str r7, [tsk, #TI_PREEMPT]
#endif
irq_handler
#ifdef CONFIG_PREEMPT
ldr r0, [tsk, #TI_PREEMPT]
str r8, [tsk, #TI_PREEMPT]
teq r0, r7
strne r0, [r0, -r0]
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on
#endif
mov why, #0
b ret_to_user
.ltorg
.align 5
其中usr_entry用于用户模式下发生中断时初始化中断处理堆栈，同时保存所有SVC态寄存器到堆栈。
.macro usr_entry
sub sp, sp, #S_FRAME_SIZE
stmib sp, {r1 - r12}
ldmia r0, {r1 - r3}
add r0, sp, #S_PC @ here for interlock avoidance
mov r4, #-1 @ "" "" "" ""
str r1, [sp] @ save the "real" r0 copied
@ from the exception stack
#if __LINUX_ARM_ARCH__ < 6 && !defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG)
#ifndef CONFIG_MMU
#warning "NPTL on non MMU needs fixing"
#else
@ make sure our user space atomic helper is aborted
cmp r2, #TASK_SIZE
bichs r3, r3, #PSR_Z_BIT
#endif
#endif
@
@ We are now ready to fill in the remaining blanks on the stack:
@
@ r2 - lr_<exception>, already fixed up for correct return/restart
@ r3 - spsr_<exception>
@ r4 - orig_r0 (see pt_regs definition in ptrace.h)
@
@ Also, separately save sp_usr and lr_usr
@
stmia r0, {r2 - r4}
stmdb r0, {sp, lr}^
@
@ Enable the alignment trap while in kernel mode
@
alignment_trap r0
@
@ Clear FP to mark the first stack frame
@
zero_fp
.endm
irq_handler也是一个宏,最终会调用asm_do_IRQ,也就是我们的处理函数
.macro irq_handler get_irqnr_preamble r5, lr 1: get_irqnr_and_base r0, r6, r5, lr movne r1, sp @ @ routine called with r0 = irq number, r1 = struct pt_regs * @ adrne lr, 1b bne asm_do_IRQ
C函数处理
asm_do_IRQ
汇编处理流程最终会进入asm_do_IRQ处理
asmlinkage void __exception asm_do_IRQ(unsigned int irq, struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
struct irq_desc *desc = irq_desc + irq;
/*
* Some hardware gives randomly wrong interrupts. Rather
* than crashing, do something sensible.
*/
if (irq >= NR_IRQS)
desc = &bad_irq_desc;
irq_enter();
desc_handle_irq(irq, desc);
/* AT91 specific workaround */
irq_finish(irq);
irq_exit();
set_irq_regs(old_regs);
}
irq_desc是中断函数处理的数组,最终处理在desc_handle_irq(irq, desc); desc是中断全局数组,irq中断号.
static inline void desc_handle_irq(unsigned int irq, struct irq_desc *desc)
{
desc->handle_irq(irq, desc);
}
也就是说,irq_desc是一个按照中断号为索引的结构体数组,里面存储各种信息包含中断入口函数handle_irq等
struct irq_desc {
irq_flow_handler_t handle_irq;
struct irq_chip *chip;
struct msi_desc *msi_desc;
void *handler_data;
void *chip_data;
struct irqaction *action; /* IRQ action list */
unsigned int status; /* IRQ status */
unsigned int depth; /* nested irq disables */
unsigned int wake_depth; /* nested wake enables */
unsigned int irq_count; /* For detecting broken IRQs */
unsigned int irqs_unhandled;
spinlock_t lock;
#ifdef CONFIG_SMP
cpumask_t affinity;
unsigned int cpu;
#endif
#if defined(CONFIG_GENERIC_PENDING_IRQ) || defined(CONFIG_IRQBALANCE)
cpumask_t pending_mask;
#endif
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *dir;
#endif
const char *name;
} ____cacheline_internodealigned_in_smp;
__set_irq_handler
那么执行函数handle_irq具体是指向了什么?kernel/irq/chip.c中设置的desc->handle_irq = handle;
void
__set_irq_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
const char *name)
{
struct irq_desc *desc;
unsigned long flags;
if (irq >= NR_IRQS) {
printk(KERN_ERR
"Trying to install type control for IRQ%d\n", irq);
return;
}
desc = irq_desc + irq;
if (!handle)
handle = handle_bad_irq;
else if (desc->chip == &no_irq_chip) {
printk(KERN_WARNING "Trying to install %sinterrupt handler "
"for IRQ%d\n", is_chained ? "chained " : "", irq);
/*
* Some ARM implementations install a handler for really dumb
* interrupt hardware without setting an irq_chip. This worked
* with the ARM no_irq_chip but the check in setup_irq would
* prevent us to setup the interrupt at all. Switch it to
* dummy_irq_chip for easy transition.
*/
desc->chip = &dummy_irq_chip;
}
spin_lock_irqsave(&desc->lock, flags);
/* Uninstall? */
if (handle == handle_bad_irq) {
if (desc->chip != &no_irq_chip)
mask_ack_irq(desc, irq);
desc->status |= IRQ_DISABLED;
desc->depth = 1;
}
desc->handle_irq = handle;
desc->name = name;
if (handle != handle_bad_irq && is_chained) {
desc->status &= ~IRQ_DISABLED;
desc->status |= IRQ_NOREQUEST | IRQ_NOPROBE;
desc->depth = 0;
desc->chip->unmask(irq);
}
spin_unlock_irqrestore(&desc->lock, flags);
}
函数__set_irq_handler被set_irq_handler调用
static inline void
set_irq_handler(unsigned int irq, irq_flow_handler_t handle)
{
__set_irq_handler(irq, handle, 0, NULL);
}
s3c24xx_init_irq
set_irq_handler被多处调用,比如在arch/arm/plat-s3c24xx/irq.c中的s3c24xx_init_irq
void __init s3c24xx_init_irq(void)
....
case IRQ_EINT4t7:
case IRQ_EINT8t23:
case IRQ_UART0:
case IRQ_UART1:
case IRQ_UART2:
case IRQ_ADCPARENT:
set_irq_chip(irqno, &s3c_irq_level_chip);
set_irq_handler(irqno, handle_level_irq);
break;
case IRQ_RESERVED6:
case IRQ_RESERVED24:
/* no IRQ here */
break;
....
set_irq_chained_handler(IRQ_EINT4t7, s3c_irq_demux_extint4t7);
set_irq_chained_handler(IRQ_EINT8t23, s3c_irq_demux_extint8);
set_irq_chained_handler(IRQ_UART0, s3c_irq_demux_uart0);
set_irq_chained_handler(IRQ_UART1, s3c_irq_demux_uart1);
set_irq_chained_handler(IRQ_UART2, s3c_irq_demux_uart2);
set_irq_chained_handler(IRQ_ADCPARENT, s3c_irq_demux_adc);
...
for (irqno = IRQ_EINT4; irqno <= IRQ_EINT23; irqno++) {
irqdbf("registering irq %d (extended s3c irq)\n", irqno);
set_irq_chip(irqno, &s3c_irqext_chip);
set_irq_handler(irqno, handle_edge_irq); ..............设置中断handler
set_irq_flags(irqno, IRQF_VALID);
}
比如我们的外部中断0处理
#define IRQ_EINT0 S3C2410_IRQ(0) /* 16 */
for (irqno = IRQ_EINT0; irqno <= IRQ_EINT3; irqno++) {
irqdbf("registering irq %d (ext int)\n", irqno);
set_irq_chip(irqno, &s3c_irq_eint0t4);
set_irq_handler(irqno, handle_edge_irq);
set_irq_flags(irqno, IRQF_VALID);
}
handle_edge_irq
也就是填充这个全局结构数组irq_desc的IRQ_EINT0项中的相关信息,这里就是填充数组16~19.也就是中断最终会调用注册的handle_irq.在中断0~3中,注册了函数handle_edge_irq为handle_irq,边沿中断处理
///kernel/irq/chip.c
void fastcall
handle_edge_irq(unsigned int irq, struct irq_desc *desc)
{
const unsigned int cpu = smp_processor_id();
spin_lock(&desc->lock);
desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
/*
* If we're currently running this IRQ, or its disabled,
* we shouldn't process the IRQ. Mark it pending, handle
* the necessary masking and go out
*/
if (unlikely((desc->status & (IRQ_INPROGRESS | IRQ_DISABLED)) ||
!desc->action)) {
desc->status |= (IRQ_PENDING | IRQ_MASKED);
mask_ack_irq(desc, irq);
goto out_unlock;
}
kstat_cpu(cpu).irqs[irq]++;
/* Start handling the irq */
desc->chip->ack(irq);
/* Mark the IRQ currently in progress.*/
desc->status |= IRQ_INPROGRESS;
do {
struct irqaction *action = desc->action;
irqreturn_t action_ret;
if (unlikely(!action)) {
desc->chip->mask(irq);
goto out_unlock;
}
/*
* When another irq arrived while we were handling
* one, we could have masked the irq.
* Renable it, if it was not disabled in meantime.
*/
if (unlikely((desc->status &
(IRQ_PENDING | IRQ_MASKED | IRQ_DISABLED)) ==
(IRQ_PENDING | IRQ_MASKED))) {
desc->chip->unmask(irq);
desc->status &= ~IRQ_MASKED;
}
desc->status &= ~IRQ_PENDING;
spin_unlock(&desc->lock);
action_ret = handle_IRQ_event(irq, action);
if (!noirqdebug)
note_interrupt(irq, desc, action_ret);
spin_lock(&desc->lock);
} while ((desc->status & (IRQ_PENDING | IRQ_DISABLED)) == IRQ_PENDING);
desc->status &= ~IRQ_INPROGRESS;
out_unlock:
spin_unlock(&desc->lock);
}
desc->chip->ack(irq);是之前设置的set_irq_chip(irqno, &s3c_irq_eint0t4);查找结构s3c_irq_eint0t4,具体也就是清中断了
static struct irq_chip s3c_irq_eint0t4 = {
.name = "s3c-ext0",
.ack = s3c_irq_ack,
.mask = s3c_irq_mask,
.unmask = s3c_irq_unmask,
.set_wake = s3c_irq_wake,
.set_type = s3c_irqext_type,
};
static inline void
s3c_irq_ack(unsigned int irqno)
{
unsigned long bitval = 1UL << (irqno - IRQ_EINT0);
__raw_writel(bitval, S3C2410_SRCPND);
__raw_writel(bitval, S3C2410_INTPND);
}
static inline void
s3c_irq_ack(unsigned int irqno)
{
unsigned long bitval = 1UL << (irqno - IRQ_EINT0);
__raw_writel(bitval, S3C2410_SRCPND);
__raw_writel(bitval, S3C2410_INTPND);
}
extern void __raw_writel(u32 b, volatile void __iomem *addr);
handle_IRQ_event
接下来重点函数handle_IRQ_event,链表操作,取出action的链表成员,执行action->handle
struct irqaction *action = desc->action; action_ret = handle_IRQ_event(irq, action);
desc->action
接着去分析action这个链表,它是desc的一个成员
struct irq_desc {
irq_flow_handler_t handle_irq;
struct irq_chip *chip; //底层芯片相关的函数,清中断,开关使能等
struct irqaction *action; /* IRQ action list */
...
}
struct irqaction {
irq_handler_t handler;
unsigned long flags;
cpumask_t mask;
const char *name;
void *dev_id;
struct irqaction *next;
int irq;
struct proc_dir_entry *dir;
};
request_irq
action函数链表由request_irq设置kernel/irq/manage.c,完成了中断引脚的设置使能等
irq:中断号 handler：处理函数 irqflags:上升沿触发，下降沿触发，边沿触发等。指定了快速中断或中断共享等中断处理属性. *devname：中断名字。通常是设备驱动程序的名称。改值用在 /proc/interrupt 系统 (虚拟) 文件上，或内核发生中断错误时使用。 dev_id 可作为共享中断时的中断区别参数，也可以用来指定中断服务函数需要参考的数据地址。也用于卸载action
int request_irq(unsigned int irq, irq_handler_t handler,
unsigned long irqflags, const char *devname, void *dev_id)
{
struct irqaction *action;
int retval;
#ifdef CONFIG_LOCKDEP
/*
* Lockdep wants atomic interrupt handlers:
*/
irqflags |= IRQF_DISABLED;
#endif
/*
* Sanity-check: shared interrupts must pass in a real dev-ID,
* otherwise we'll have trouble later trying to figure out
* which interrupt is which (messes up the interrupt freeing
* logic etc).
*/
if ((irqflags & IRQF_SHARED) && !dev_id)
return -EINVAL;
if (irq >= NR_IRQS)
return -EINVAL;
if (irq_desc[irq].status & IRQ_NOREQUEST)
return -EINVAL;
if (!handler)
return -EINVAL;
action = kmalloc(sizeof(struct irqaction), GFP_ATOMIC);
if (!action)
return -ENOMEM;
action->handler = handler;
action->flags = irqflags;
cpus_clear(action->mask);
action->name = devname;
action->next = NULL;
action->dev_id = dev_id;
select_smp_affinity(irq);
#ifdef CONFIG_DEBUG_SHIRQ
if (irqflags & IRQF_SHARED) {
/*
* It's a shared IRQ -- the driver ought to be prepared for it
* to happen immediately, so let's make sure....
* We do this before actually registering it, to make sure that
* a 'real' IRQ doesn't run in parallel with our fake
*/
if (irqflags & IRQF_DISABLED) {
unsigned long flags;
local_irq_save(flags);
handler(irq, dev_id);
local_irq_restore(flags);
} else
handler(irq, dev_id);
}
#endif
retval = setup_irq(irq, action);
if (retval)
kfree(action);
return retval;
}
这里分配一个action成员,将传递的参数赋值到action的成员然后使用setup_irq(irq, action);设置
setup_irq
判断是否为共享中断,所谓共享中断也就是中断源一样的中断,共享中断只能加入共享中断的链表中.接着设置引脚等
int setup_irq(unsigned int irq, struct irqaction *new)
{
struct irq_desc *desc = irq_desc + irq;
struct irqaction *old, **p;
const char *old_name = NULL;
unsigned long flags;
int shared = 0;
if (irq >= NR_IRQS)
return -EINVAL;
if (desc->chip == &no_irq_chip)
return -ENOSYS;
/*
* Some drivers like serial.c use request_irq() heavily,
* so we have to be careful not to interfere with a
* running system.
*/
if (new->flags & IRQF_SAMPLE_RANDOM) {
/*
* This function might sleep, we want to call it first,
* outside of the atomic block.
* Yes, this might clear the entropy pool if the wrong
* driver is attempted to be loaded, without actually
* installing a new handler, but is this really a problem,
* only the sysadmin is able to do this.
*/
rand_initialize_irq(irq);
}
/*
* The following block of code has to be executed atomically
*/
spin_lock_irqsave(&desc->lock, flags);
p = &desc->action;
old = *p;
if (old) {
/*
* Can't share interrupts unless both agree to and are
* the same type (level, edge, polarity). So both flag
* fields must have IRQF_SHARED set and the bits which
* set the trigger type must match.
*/
if (!((old->flags & new->flags) & IRQF_SHARED) ||
((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
old_name = old->name;
goto mismatch;
}
#if defined(CONFIG_IRQ_PER_CPU)
/* All handlers must agree on per-cpuness */
if ((old->flags & IRQF_PERCPU) !=
(new->flags & IRQF_PERCPU))
goto mismatch;
#endif
/* add new interrupt at end of irq queue */
do {
p = &old->next;
old = *p;
} while (old);
shared = 1;
}
*p = new;
/* Exclude IRQ from balancing */
if (new->flags & IRQF_NOBALANCING)
desc->status |= IRQ_NO_BALANCING;
if (!shared) {
irq_chip_set_defaults(desc->chip);
#if defined(CONFIG_IRQ_PER_CPU)
if (new->flags & IRQF_PERCPU)
desc->status |= IRQ_PER_CPU;
#endif
/* Setup the type (level, edge polarity) if configured: */
if (new->flags & IRQF_TRIGGER_MASK) {
if (desc->chip && desc->chip->set_type)
desc->chip->set_type(irq,
new->flags & IRQF_TRIGGER_MASK);
else
/*
* IRQF_TRIGGER_* but the PIC does not support
* multiple flow-types?
*/
printk(KERN_WARNING "No IRQF_TRIGGER set_type "
"function for IRQ %d (%s)\n", irq,
desc->chip ? desc->chip->name :
"unknown");
} else
compat_irq_chip_set_default_handler(desc);
desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING |
IRQ_INPROGRESS);
if (!(desc->status & IRQ_NOAUTOEN)) {
desc->depth = 0;
desc->status &= ~IRQ_DISABLED;
if (desc->chip->startup)
desc->chip->startup(irq);
else
desc->chip->enable(irq);
} else
/* Undo nested disables: */
desc->depth = 1;
}
/* Reset broken irq detection when installing new handler */
desc->irq_count = 0;
desc->irqs_unhandled = 0;
spin_unlock_irqrestore(&desc->lock, flags);
new->irq = irq;
register_irq_proc(irq);
new->dir = NULL;
register_handler_proc(irq, new);
return 0;
mismatch:
#ifdef CONFIG_DEBUG_SHIRQ
if (!(new->flags & IRQF_PROBE_SHARED)) {
printk(KERN_ERR "IRQ handler type mismatch for IRQ %d\n", irq);
if (old_name)
printk(KERN_ERR "current handler: %s\n", old_name);
dump_stack();
}
#endif
spin_unlock_irqrestore(&desc->lock, flags);
return -EBUSY;
}
这里desc->chip->set_type调用设置中断的引脚寄存器等,是在初始化中s3c24xx_init_irq赋值过的chip,通过request_irq传递的flag指定触发模式等
static struct irq_chip s3c_irqext_chip = {
.name = "s3c-ext",
.mask = s3c_irqext_mask,
.unmask = s3c_irqext_unmask,
.ack = s3c_irqext_ack,
.set_type = s3c_irqext_type,
.set_wake = s3c_irqext_wake
};
static struct irq_chip s3c_irq_eint0t4 = {
.name = "s3c-ext0",
.ack = s3c_irq_ack,
.mask = s3c_irq_mask,
.unmask = s3c_irq_unmask,
.set_wake = s3c_irq_wake,
.set_type = s3c_irqext_type,
};
int
s3c_irqext_type(unsigned int irq, unsigned int type)
{
void __iomem *extint_reg;
void __iomem *gpcon_reg;
unsigned long gpcon_offset, extint_offset;
unsigned long newvalue = 0, value;
if ((irq >= IRQ_EINT0) && (irq <= IRQ_EINT3))
{
gpcon_reg = S3C2410_GPFCON;
extint_reg = S3C24XX_EXTINT0;
gpcon_offset = (irq - IRQ_EINT0) * 2;
extint_offset = (irq - IRQ_EINT0) * 4;
}
else if ((irq >= IRQ_EINT4) && (irq <= IRQ_EINT7))
{
gpcon_reg = S3C2410_GPFCON;
extint_reg = S3C24XX_EXTINT0;
gpcon_offset = (irq - (EXTINT_OFF)) * 2;
extint_offset = (irq - (EXTINT_OFF)) * 4;
}
else if ((irq >= IRQ_EINT8) && (irq <= IRQ_EINT15))
{
gpcon_reg = S3C2410_GPGCON;
extint_reg = S3C24XX_EXTINT1;
gpcon_offset = (irq - IRQ_EINT8) * 2;
extint_offset = (irq - IRQ_EINT8) * 4;
}
else if ((irq >= IRQ_EINT16) && (irq <= IRQ_EINT23))
{
gpcon_reg = S3C2410_GPGCON;
extint_reg = S3C24XX_EXTINT2;
gpcon_offset = (irq - IRQ_EINT8) * 2;
extint_offset = (irq - IRQ_EINT16) * 4;
} else
return -1;
/* Set the GPIO to external interrupt mode */
value = __raw_readl(gpcon_reg);
value = (value & ~(3 << gpcon_offset)) | (0x02 << gpcon_offset);
__raw_writel(value, gpcon_reg);
/* Set the external interrupt to pointed trigger type */
switch (type)
{
case IRQT_NOEDGE:
printk(KERN_WARNING "No edge setting!\n");
break;
case IRQT_RISING:
newvalue = S3C2410_EXTINT_RISEEDGE;
break;
case IRQT_FALLING:
newvalue = S3C2410_EXTINT_FALLEDGE;
break;
case IRQT_BOTHEDGE:
newvalue = S3C2410_EXTINT_BOTHEDGE;
break;
case IRQT_LOW:
newvalue = S3C2410_EXTINT_LOWLEV;
break;
case IRQT_HIGH:
newvalue = S3C2410_EXTINT_HILEV;
break;
default:
printk(KERN_ERR "No such irq type %d", type);
return -1;
}
value = __raw_readl(extint_reg);
value = (value & ~(7 << extint_offset)) | (newvalue << extint_offset);
__raw_writel(value, extint_reg);
return 0;
}
free_irq
关闭中断,也就是取消中断处理函数,在全局数组irq_desc寻找到对应的action链表,通过id将其从链表中删除.如果链表空了,则禁止中断
void free_irq(unsigned int irq, void *dev_id)
小结
流程
start_kernel中调用trap_init拷贝向量表到0xffff0000- 触发中断,进入中断向量表
vector_irq跳转进入保存现场,跳转到__irq_usr__irq_usr调用usr_entry进行用户模式下发生中断时初始化中断处理堆栈,通过irq_handler调用asm_do_IRQ进入C函数处理asm_do_IRQ寻找irq_desc 数组,调用desc->handle_irq来执行irq_desc数组中的入口函数handle_irq,这里外中断的话执行的是handle_edge_irq- 中断入口函数清中断,执行
action中的链表函数 action中会判断是否为共享中断,设置中断类型,引脚寄存器等,同时开启中断- 使用
free_irq卸载掉链表中的函数,如果链表函数空了则关中断
设置irq_desc数组
- 在
s3c24xx_init_irq中进行数组的初始化 set_irq_chip初始化数组中的chip结构set_irq_handler设置中断入口函数handle_irqrequest_irq来创建action链表,分配空间,并加入链表struct irq_chip *chip;这是底层芯片相关的函数,清中断,开关使能等
关键结构成员
struct irq_desc {
irq_flow_handler_t handle_irq; //中断入口函数,在外中断指向了 handle_edge_irq
struct irq_chip *chip; //芯片底层处理函数,指向s3c_irqex_chip
struct irqaction *action; //具体执行函数的链表,会被handle_irq 入口函数使用的
}
struct irq_chip {
const char *name;
unsigned int (*startup)(unsigned int irq); //启动中断
void (*shutdown)(unsigned int irq); //关闭中断
void (*enable)(unsigned int irq); //使能中断
void (*disable)(unsigned int irq); //禁止中断
void (*ack)(unsigned int irq); //响应中断,清中断
}
struct irqaction {
irq_handler_t handler; //action的执行函数
unsigned long flags; //标志,用于设置中断边沿等
};
完整框架图
流程一览
设置向量表
设置全局中断数组
设置用户action动作
来源：https://www.cnblogs.com/zongzi10010/p/10003477.html