原文:
1 中断初始化
参见 arch\arm\mach-s3c2410\Irq.c
void __init s3c24xx_init_irq(void)
{
…
/* 1. 清除所有pending的中断 */
last = 0;
for (i = 0; i
pend = __raw_readl(S3C24XX_EINTPEND);
if (pend == 0 || pend == last)
break;
__raw_writel(pend, S3C24XX_EINTPEND);
printk("irq: clearing pending ext status %08x\n", (int)pend);
last = pend;
}
last = 0;
for (i = 0; i
pend = __raw_readl(S3C2410_INTPND);
if (pend == 0 || pend == last)
break;
__raw_writel(pend, S3C2410_SRCPND);
__raw_writel(pend, S3C2410_INTPND);
printk("irq: clearing pending status %08x\n", (int)pend);
last = pend;
}
last = 0;
for (i = 0; i
pend = __raw_readl(S3C2410_SUBSRCPND);
if (pend == 0 || pend == last)
break;
printk("irq: clearing subpending status %08x\n", (int)pend);
__raw_writel(pend, S3C2410_SUBSRCPND);
last = pend;
}
/* 注册中断处理函数. */
irqdbf("s3c2410_init_irq: registering s3c2410 interrupt handlers\n");
for (irqno = IRQ_EINT4t7; irqno
/* set all the s3c2410 internal irqs */
switch (irqno) {
/* 这几个中断是级联的,所以中断例程也不一样.*/
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, do_level_IRQ); /*这个中断例程在后面会被重新设置*/
break;
case IRQ_RESERVED6:
case IRQ_RESERVED24:
/* no IRQ here */
break;
default:
//irqdbf("registering irq %d (s3c irq)\n", irqno);
set_irq_chip(irqno, &s3c_irq_chip);
set_irq_handler(irqno, do_edge_IRQ); /*对于不是级联的中断,这个就是中断例程.*/
set_irq_flags(irqno, IRQF_VALID);
}
}
/* 重新设置级联的中断例程*/
set_irq_chained_handler(IRQ_EINT4t7, s3c_irq_demux_extint);
set_irq_chained_handler(IRQ_EINT8t23, s3c_irq_demux_extint);
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);
/* 为外部中断设置中断例程*/
for (irqno = IRQ_EINT0; irqno
irqdbf("registering irq %d (ext int)\n", irqno);
set_irq_chip(irqno, &s3c_irq_eint0t4);
set_irq_handler(irqno, do_edge_IRQ);
set_irq_flags(irqno, IRQF_VALID);
}
for (irqno = IRQ_EINT4; irqno
irqdbf("registering irq %d (extended s3c irq)\n", irqno);
set_irq_chip(irqno, &s3c_irqext_chip);
set_irq_handler(irqno, do_edge_IRQ);
set_irq_flags(irqno, IRQF_VALID);
}
/* 为UART设置中断例程,*/
irqdbf("s3c2410: registering external interrupts\n");
for (irqno = IRQ_S3CUART_RX0; irqno
irqdbf("registering irq %d (s3c uart0 irq)\n", irqno);
set_irq_chip(irqno, &s3c_irq_uart0);
set_irq_handler(irqno, do_level_IRQ);
set_irq_flags(irqno, IRQF_VALID);
}
for (irqno = IRQ_S3CUART_RX1; irqno
irqdbf("registering irq %d (s3c uart1 irq)\n", irqno);
set_irq_chip(irqno, &s3c_irq_uart1);
set_irq_handler(irqno, do_level_IRQ);
set_irq_flags(irqno, IRQF_VALID);
}
for (irqno = IRQ_S3CUART_RX2; irqno
irqdbf("registering irq %d (s3c uart2 irq)\n", irqno);
set_irq_chip(irqno, &s3c_irq_uart2);
set_irq_handler(irqno, do_level_IRQ);
set_irq_flags(irqno, IRQF_VALID);
}
for (irqno = IRQ_TC; irqno
irqdbf("registering irq %d (s3c adc irq)\n", irqno);
set_irq_chip(irqno, &s3c_irq_adc);
set_irq_handler(irqno, do_edge_IRQ);
set_irq_flags(irqno, IRQF_VALID);
}
irqdbf("s3c2410: registered interrupt handlers\n");
}
所谓级联的中断, 即指有几个中断共用同一个中断线, 比如EINT4-EINT7就共用一个中断线:EINT4_7.
假如现在系统产生一个EINT4的中断, 大致的中断流程顺序是: …-> s3c_irq_demux_extint ->
do_edge_IRQ -> 我们注册的中断例程. 后面我们会详细讲解.
接下来我们主要set_irq_handle()函数, set_irq_chip()主要用来设置对这个中断mask, unmask等操作的函数, 它们会在适当的地方被调用.
static inline void
set_irq_handler(unsigned int irq,
void fastcall (*handle)(unsigned int, struct irq_desc *,
struct pt_regs *))
{
__set_irq_handler(irq, handle, 0);
}
void
__set_irq_handler(unsigned int irq,
void fastcall (*handle)(unsigned int, irq_desc_t *,
struct pt_regs *),
int is_chained)
{
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;
}
/* irq_desc 是一个静态数组,存放每个中断信息*/
desc = irq_desc + irq;
if (!handle)
handle = handle_bad_irq;
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) {
desc->chip->mask(irq);
desc->chip->ack(irq);
}
desc->status |= IRQ_DISABLED;
desc->depth = 1;
}
desc->handle_irq = handle; /*保存中断例程*/
if (handle != handle_bad_irq && is_chained) {
desc->status &= ~IRQ_DISABLED;
desc->status |= IRQ_NOREQUEST | IRQ_NOPROBE;
desc->depth = 0;
desc->chip->unmask(irq); /*对于级联的中断会先调用unmask来打开中断*/
}
spin_unlock_irqrestore(&desc->lock, flags);
}
每个中断都有一个irq_desc的对象来描述它,这里面保存了这个中断的状态,处理函数等信息.
当中断产生时比如EINT4, 大致的流程如下:
先调用在初始化里注册好的s3c_irq_demux_extint() (EINT4,EINT5,EINT6,EINT7都先调用它)
static void
s3c_irq_demux_extint(unsigned int irq,
struct irqdesc *desc,
struct pt_regs *regs)
{
unsigned long eintpnd = __raw_readl(S3C24XX_EINTPEND); /*先获取具体是哪个EINT产生中断.*/
unsigned long eintmsk = __raw_readl(S3C24XX_EINTMASK);
eintpnd &= ~eintmsk; /*检查是否被屏蔽了*/
if (eintpnd) {
irq = fls(eintpnd); /*获取相对于EINT0的中断号*/
irq += (IRQ_EINT4 - (4 + 1)); /*算出在整个中断控制器下的中断号, 这里就是IRQ_EINT4*/
desc_handle_irq(irq, irq_desc + irq, regs); /*以IRQ_EINT4调用这个函数.*/
}
}
Static inline void desc_handle_irq(unsigned int irq, struct irq_desc *desc, struct pt_regs *regs)
{
/*这里的desc就代表的是EINT4, 所以这里实际调用了do_edge_IRQ(在初始化时注册的) */
desc->handle_irq(irq, desc, regs);
}
#define do_edge_IRQ handle_edge_irq
void fastcall
handle_edge_irq(unsigned int irq, struct irq_desc *desc, struct pt_regs *regs)
{
const unsigned int cpu = smp_processor_id();
spin_lock(&desc->lock);
desc->status &= ~(IRQ_REPLAY | IRQ_WAITING); /*修改状态*/
/*
* 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); /*清除中断标记*/
/* Mark the IRQ currently in progress.*/
desc->status |= IRQ_INPROGRESS; /*设置状态*/
do {
struct irqaction *action = desc->action; /*这个action会在以后介绍*/
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, regs, action); /*处理具体中断*/
if (!noirqdebug)
note_interrupt(irq, desc, action_ret, regs);
spin_lock(&desc->lock);
} while ((desc->status & (IRQ_PENDING | IRQ_DISABLED)) == IRQ_PENDING);
desc->status &= ~IRQ_INPROGRESS;
out_unlock:
spin_unlock(&desc->lock);
}
irqreturn_t handle_IRQ_event(unsigned int irq, struct pt_regs *regs, struct irqaction *action)
{
….
ret = action->handler(irq, action->dev_id, regs);
….
}
其中action->handler就是我们用request_irq()注册的我们自己的中断例程. 具体原理可以参考这个函数的实现.
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