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nmi watch dog , check_timer

分类： LINUX

2010-05-09 23:23:36

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 »  »  »  »  » setup_IO_APIC末尾处，check_timer是啥意思啊？
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setup_IO_APIC末尾处，check_timer是啥意思啊？
 -  [2007-11-26 18:12 | 5,256 byte(s)]
 
 -  [2007-11-27 09:59 | 5,137 byte(s)]
 
Subject: setup_IO_APIC末尾处，check_timer是啥意思啊？ 
Author:     Posted: 2007-11-26 18:12    Length: 5,256 byte(s)
[] [Print] 
我列的是2.4.32版，代码如下 


static inline void check_timer(void)

{

	extern int timer_ack;

	int pin1, pin2;

	int vector;



	disable_8259A_irq(0);

	vector = assign_irq_vector(0);

	set_intr_gate(vector, interrupt[0]);



	apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);

	init_8259A(1);

	timer_ack = 1;

	enable_8259A_irq(0);



	pin1 = find_isa_irq_pin(0, mp_INT);

	pin2 = find_isa_irq_pin(0, mp_ExtINT);



	printk(KERN_INFO "..TIMER: vector=0x%02X pin1=%d pin2=%d
", vector, pin1, pin2);



	if (pin1 != -1) {

		unmask_IO_APIC_irq(0);

		if (timer_irq_works()) {

			if (nmi_watchdog == NMI_IO_APIC) {

				disable_8259A_irq(0);

				setup_nmi();

				enable_8259A_irq(0);

				check_nmi_watchdog();

			}

			return;

		}

		clear_IO_APIC_pin(0, pin1);

		printk(KERN_ERR "..MP-BIOS bug: 8254 timer not connected to IO-APIC
");

	}



	printk(KERN_INFO "...trying to set up timer (IRQ0) through the 8259A ... ");

	if (pin2 != -1) {

		printk("
..... (found pin %d) ...", pin2);

		setup_ExtINT_IRQ0_pin(pin2, vector);

		if (timer_irq_works()) {

			printk("works.
");

			if (pin1 != -1)

				replace_pin_at_irq(0, 0, pin1, 0, pin2);

			else

				add_pin_to_irq(0, 0, pin2);

			if (nmi_watchdog == NMI_IO_APIC) {

				setup_nmi();

				check_nmi_watchdog();

			}

			return;

		}

		clear_IO_APIC_pin(0, pin2);

	}

	printk(" failed.
");



	if (nmi_watchdog) {

		printk(KERN_WARNING "timer doesn't work through the IO-APIC - disabling NMI

Watchdog!
");

		nmi_watchdog = 0;

	}



	printk(KERN_INFO "...trying to set up timer as Virtual Wire IRQ...");



	disable_8259A_irq(0);

	irq_desc[0].handler = &lapic_irq_type;

	apic_write_around(APIC_LVT0, APIC_DM_FIXED | vector);	/* Fixed mode */

	enable_8259A_irq(0);



	if (timer_irq_works()) {

		printk(" works.
");

		return;

	}

	apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_FIXED | vector);

	printk(" failed.
");



	printk(KERN_INFO "...trying to set up timer as ExtINT IRQ...");



	init_8259A(0);

	make_8259A_irq(0);

	apic_write_around(APIC_LVT0, APIC_DM_EXTINT);



	unlock_ExtINT_logic();



	if (timer_irq_works()) {

		printk(" works.
");

		return;

	}

	printk(" failed 
src="http://www.linuxforum.net/forum/images/icons/frown.gif">.
");

	panic("IO-APIC + timer doesn't work! pester 

}





以下根据我个人的理解： 

进入时的初始状态是 
1） BP的LINT0启用，AP的LINT0屏蔽 
2） IO APIC 中，所有对应mp_INT的管脚启用，所有对应mp_ExtINT的管脚屏蔽 
3） 8259中，部分未连接至IO APIC，只连接至8259的IRQ启用 

函数check_timer的流程是： 

第一部分: 假设，Timer作为mp_INT，连接至IO APIC。 
操作，Local APIC的LINT0屏蔽，IO APIC的pin1作为mp_INT启用，8259的IRQ0启用 
疑问，为什么8259的IRQ0启用？谁来给8259一个INTA信号？ 

第二部分: 假设，BIOS错误，timer事实上作为mp_INT连接至IO 
APIC，但mp_floating_table中显示的是Ext_INT。 
对应，printk(KERN_INFO "...trying to set up timer (IRQ0) through the 8259A 
... "); 
操作，Local APIC的LINT0屏蔽，IO 
APIC的pin2作为mp_INT启用，8259的IRQ0启用 
疑问，为什么8259的IRQ0启用？而且这个假设和printk中的提示不是驴唇不对马嘴么？ 

第三部分: 假设，Timer直连BP的LINT0。 
对应，printk(KERN_INFO "...trying to set up timer as Virtual Wire IRQ..."); 
操作，Local APIC的LINT0作为Fixed启用，而不是作为ExtINT，IO 
APIC的pin1和pin2屏蔽，8259的IRQ0启用 
疑问，为什么8259的IRQ0启用？而且这个假设和printk中的提示驴唇不对马嘴。 

第四部分: 假设，Timer连8259，8259连BP的LINT0。 
对应，printk(KERN_INFO "...trying to set up timer as ExtINT IRQ..."); 
操作，Local APIC的LINT0作为Ext_INT启用，IO 
APIC的pin1和pin2屏蔽，8259的IRQ0启用 

疑问，这次我到是明白为什么启用8259，但是问题在于随后的unlock_ExtINT_logic，注释的意思� 
孟笫鞘止じ�8259一个INTA，这是为什么？而且这个假设和printk中的提示驴唇不对马嘴。 

[] [Print] 
Subject: Re: setup_IO_APIC末尾处，check_timer是啥意思啊？ 
Author:     Posted: 2007-11-27 09:59    Length: 5,137 byte(s)
[] [Print] 
我以前的注释，自己也忘了什么意思了，呵呵 


/*

 * This code may look a bit paranoid, but it's supposed to cooperate with

 * a wide range of boards and BIOS bugs.  Fortunately only the timer IRQ

 * is so screwy.  Thanks to Brian Perkins for testing/hacking this beast

 幸运的是只有定时器IRQ有点怪僻的

 * fanatically on his truly buggy board.

 */

static inline void check_timer(void)

{

	extern int timer_ack;

	int pin1, pin2;

	int vector;



	/*

	 * get/set the timer IRQ vector:

	 */

	disable_8259A_irq(0);

	vector = assign_irq_vector(0);

	set_intr_gate(vector, interrupt[0]);



	/*

	 * Subtle, code in do_timer_interrupt() expects an AEOI

	 * mode for the 8259A whenever interrupts are routed

	 * through I/O APICs.  Also IRQ0 has to be enabled in

	 * the 8259A which implies the virtual wire has to be

	 * disabled in the local APIC.

	 */

	 //禁用LVT0

	apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);

	init_8259A(1);//aeoi

	timer_ack = 1;//需要ack

	enable_8259A_irq(0);//enable,但是LVT0和ioapic被禁用



	pin1 = find_isa_irq_pin(0, mp_INT);

	pin2 = find_isa_irq_pin(0, mp_ExtINT);



	//..TIMER: vector=0x31 pin1=2 pin2=0

/*

index	type	irqtype	irqflag	srcbus	srcbusirq	dstapic	dstirq	trigg	IRQ		Vec

5		03		03(Ext)	05 	00	02		00			04		00		edge	00	

7		03		00		05 	00	02		00			04		02		edge	00		31

*/

	printk(KERN_INFO "..TIMER: vector=%d pin1=%d pin2=%d
", vector, pin1, pin2);



	if (pin1 != -1) {

		/*说明IRQ0是通过IOAPIC

		 * Ok, does IRQ0 through the IOAPIC work?

		 */

		unmask_IO_APIC_irq(0);//开启中断,重定向表已经在前面设定了

		if (timer_irq_works()) {

			if (nmi_watchdog) {

				disable_8259A_irq(0);

				setup_nmi();//并不还原,??????????

				enable_8259A_irq(0);

				nmi_irq_works();				

			}

			return;

		}

		//失败，清除重定向表

		clear_IO_APIC_pin(0, pin1);

		//..MP-BIOS bug: 8254 timer not connected to IO-APIC

		//...trying to set up timer (IRQ0) through the 8259A ... 

		//..... (found pin 0) ...works.



		//MPBIOS的配置指出了，怎么会是bug?

		printk(KERN_ERR "..MP-BIOS bug: 8254 timer not connected to IO-APIC
");

	}



	printk(KERN_INFO "...trying to set up timer (IRQ0) through the 8259A ... ");

	if (pin2 != -1) {//主8259A的INTR接到pin上

		printk("
..... (found pin %d) ...", pin2);

		/*

		 * legacy devices should be connected to IO APIC #0

		 */

		//通过ExtInt试图开启timer

		setup_ExtINT_IRQ0_pin(pin2, vector);

		if (timer_irq_works()) {

			printk("works.
");

			if (nmi_watchdog) {

				setup_nmi();

				nmi_irq_works();

			}

			return;

		}

		/*

		 * Cleanup, just in case ...

		 */

		//失败，清除重定向表

		clear_IO_APIC_pin(0, pin2);

	}

	printk(" failed.
");



	if (nmi_watchdog) {

		printk(KERN_WARNING "timer doesnt work through the IO-APIC - disabling NMI

Watchdog!
");

		nmi_watchdog = 0;

	}



	printk(KERN_INFO "...trying to set up timer as Virtual Wire IRQ...");



	disable_8259A_irq(0);

	irq_desc[0].handler = &lapic_irq_type;

	//假设IRQ0直接连在line0上，目前只有timer(IRQ0)被启用

	apic_write_around(APIC_LVT0, APIC_DM_FIXED | vector);	/* Fixed mode */

	enable_8259A_irq(0);



	if (timer_irq_works()) {

		printk(" works.
");

		return;

	}

	//禁用

	apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_FIXED | vector);

	printk(" failed.
");



	printk(KERN_INFO "...trying to set up timer as ExtINT IRQ...");



	init_8259A(0);//no aeoi

	make_8259A_irq(0);

	//假设IRQ0通过8259A连在line0上,目前只有timer(IRQ0)被启用

	apic_write_around(APIC_LVT0, APIC_DM_EXTINT);



	//??????启动ExtInt模式

	unlock_ExtINT_logic();



	if (timer_irq_works()) {

		printk(" works.
");

		return;

	}

	printk(" failed 
src="http://www.linuxforum.net/forum/images/icons/frown.gif">.
");

	panic("IO-APIC + timer doesn't work! pester 

}
----
Good better best,never let it rest.
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