三读内核中断处理（4）：几个特定的中断处理函数
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本文适用于
ADSP-BF561
uclinux-2008r1.5-rc3(smp patch)
Visual DSP++ 5.0(update 5)
欢迎转载，但请保留作者信息
1.1 handle_simple_irq
对于不同中断源的默认处理函数(irq_desc结构体中的handle_irq)，内核将之分成了3类。除了PF0-PF47的中断和IRQ_PROG0_INTA、IRQ_PROG1_INTA、IRQ_PROG2_INTA这三个由PF口共享的中断外对于其它的中断源则使用handle_simple_irq进行处理。
handle_simple_irq函数位于kernel/irq/chip.c：
/**
* handle_simple_irq - Simple and software-decoded IRQs.
* @irq: the interrupt number
* @desc: the interrupt description structure for this irq
*
* Simple interrupts are either sent from a demultiplexing interrupt
* handler or come from hardware, where no interrupt hardware control
* is necessary.
*
* Note: The caller is expected to handle the ack, clear, mask and
* unmask issues if necessary.
*/
void fastcall
handle_simple_irq(unsigned int irq, struct irq_desc *desc)
{
struct irqaction *action;
irqreturn_t action_ret;
const unsigned int cpu = smp_processor_id();
spin_lock(&desc->lock);
if (unlikely(desc->status & IRQ_INPROGRESS))
goto out_unlock;
kstat_cpu(cpu).irqs[irq]++;
action = desc->action;
if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
if (desc->chip->mask)
desc->chip->mask(irq);
desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
desc->status |= IRQ_PENDING;
goto out_unlock;
}
desc->status &= ~(IRQ_REPLAY | IRQ_WAITING | IRQ_PENDING);
desc->status |= IRQ_INPROGRESS;
spin_unlock(&desc->lock);
action_ret = handle_IRQ_event(irq, action);
if (!noirqdebug)
note_interrupt(irq, desc, action_ret);
spin_lock(&desc->lock);
desc->status &= ~IRQ_INPROGRESS;
out_unlock:
spin_unlock(&desc->lock);
}
从这个函数的代码可以看出，这个函数的作用就是调用handle_IRQ_event，并更新desc中的状态。在中断初始化完成的时候，除了EVT_TMR之外，其它的中断源的action都为NULL，因此对大部分中断源造成的中断此函数将直接返回。
下面看看handle_IRQ_event的实现：
/**
* handle_IRQ_event - irq action chain handler
* @irq: the interrupt number
* @action: the interrupt action chain for this irq
*
* Handles the action chain of an irq event
*/
irqreturn_t handle_IRQ_event(unsigned int irq, struct irqaction *action)
{
irqreturn_t ret, retval = IRQ_NONE;
unsigned int status = 0;
handle_dynamic_tick(action);
if (!(action->flags & IRQF_DISABLED))
local_irq_enable_in_hardirq();
do {
ret = action->handler(irq, action->dev_id);
if (ret == IRQ_HANDLED)
status |= action->flags;
retval |= ret;
action = action->next;
} while (action);
if (status & IRQF_SAMPLE_RANDOM)
add_interrupt_randomness(irq);
local_irq_disable();
return retval;
}
很简单，就是按顺序调用action链表中的处理函数。
1.2 handle_level_irq
这个函数用于处理PF0-PF47产生的中断。
/**
* handle_level_irq - Level type irq handler
* @irq: the interrupt number
* @desc: the interrupt description structure for this irq
*
* Level type interrupts are active as long as the hardware line has
* the active level. This may require to mask the interrupt and unmask
* it after the associated handler has acknowledged the device, so the
* interrupt line is back to inactive.
*/
void fastcall
handle_level_irq(unsigned int irq, struct irq_desc *desc)
{
unsigned int cpu = smp_processor_id();
struct irqaction *action;
irqreturn_t action_ret;
spin_lock(&desc->lock);
mask_ack_irq(desc, irq);
if (unlikely(desc->status & IRQ_INPROGRESS))
goto out_unlock;
desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
kstat_cpu(cpu).irqs[irq]++;
/*
* If its disabled or no action available
* keep it masked and get out of here
*/
action = desc->action;
if (unlikely(!action || (desc->status & IRQ_DISABLED)))
goto out_unlock;
desc->status |= IRQ_INPROGRESS;
spin_unlock(&desc->lock);
action_ret = handle_IRQ_event(irq, action);
if (!noirqdebug)
note_interrupt(irq, desc, action_ret);
spin_lock(&desc->lock);
desc->status &= ~IRQ_INPROGRESS;
if (!(desc->status & IRQ_DISABLED) && desc->chip->unmask)
desc->chip->unmask(irq);
out_unlock:
spin_unlock(&desc->lock);
}
实际上这个函数仍将调用handle_IRQ_event进行后继的处理。
1.3 bf561_demux_gpio_irq
这个函数用于处理三个复用的PF中断。
static void bf561_demux_gpio_irq(unsigned int inta_irq,
struct irq_desc *intb_desc)
{
int irq, flag_d, mask;
u16 gpio;
switch (inta_irq) {
case IRQ_PROG0_INTA:
irq = IRQ_PF0;
break;
case IRQ_PROG1_INTA:
irq = IRQ_PF16;
break;
case IRQ_PROG2_INTA:
irq = IRQ_PF32;
break;
default:
dump_stack();
return;
}
gpio = irq - IRQ_PF0;
flag_d = get_gpiop_data(gpio);
mask = flag_d & (gpio_enabled[gpio_bank(gpio)] &
get_gpiop_maska(gpio));
do {
if (mask & 1) {
struct irq_desc *desc = irq_desc + irq;
desc->handle_irq(irq, desc);
}
irq++;
mask >>= 1;
} while (mask);
}