Re: about cs5536 interrupt ack

[Songmao Tian <tiansm@lemote.com>]

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8259 problem  seems to be done with the attached patch, IDE hung seems 
to be the dma setting problem.

Thanks all for your advise, comments. I have learned a lot. now I 
continue to trace down the IDE problem.

Mao

Maciej W. Rozycki wrote:
> On Wed, 11 Jul 2007, Songmao Tian wrote:
>
>   
>>> Huh?  Have you managed to find an 8259A clone *that* broken?  So what does
>>> it return if you write 0xc to the address 0x20 in the I/O port space and
>>> then read back from that location?  You should complain to the 
>>>   
>>>       
>> It's the value of IRR, so guess IRR. AMD has well documented cs5536, I
>> appreciate that.
>>     
>
>  Indeed.  I am surprised they have decided to drop the poll command -- it 
> surely does not require much logic as it mostly reuses what's used to 
> produce the vector anyway and it is commonly used when 8259A 
> implementations are interfaced to non-i386 processors.  PPC is another 
> example.
>
>   
>>> More or less -- 3-5 should probably be the outcome of a single read
>>> transaction from the north bridge.  I.e. you issue a read to a "magic"
>>> location, 3-5 happen, and the data value returned is the vector presented by
>>> the interrupt controller on the PCI bus.
>>>   
>>>       
>> yeah, we can implement a register in north bridge.
>>     
>
>  Strictly speaking it would not be a register, but a "PCI INTA address 
> space" much like PCI memory or I/O port address spaces.  Though as the 
> former ignores addresses driven on the bus, the space occupied does not 
> have to be extensive -- I would assume whatever slot size is available 
> with the address decoder you have implemented would do.
>
>   
>>> You can still dispatch interrupts manually by examining the IRR register,
>>> but having a way to ask the 8259A's prioritiser would be nice.  Although
>>> given such a lethal erratum you report I would not count on the prioritiser
>>> to provide any useful flexibility...
>>>   
>>>       
>> yeah, that's a straight thought, tried but failed:(, patch followed.
>>     
>
>  You may have to modify other functions from arch/mips/kernel/i8259.c; 
> yes, this makes the whole experience not as pretty as one would hope...
>
>   Maciej
>
>
>
>   


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diff --git a/arch/mips/kernel/i8259.c b/arch/mips/kernel/i8259.c
index 9c79703..fd7f4ba 100644
--- a/arch/mips/kernel/i8259.c
+++ b/arch/mips/kernel/i8259.c
@@ -47,11 +47,7 @@ static struct irq_chip i8259A_chip = {
 /*
  * This contains the irq mask for both 8259A irq controllers,
  */
-static unsigned int cached_irq_mask = 0xffff;
-
-#define cached_master_mask	(cached_irq_mask)
-#define cached_slave_mask	(cached_irq_mask >> 8)
-
+unsigned int cached_irq_mask = 0xffff;
 void disable_8259A_irq(unsigned int irq)
 {
 	unsigned int mask;
diff --git a/include/asm-mips/i8259.h b/include/asm-mips/i8259.h
index e88a016..e7dcf7b 100644
--- a/include/asm-mips/i8259.h
+++ b/include/asm-mips/i8259.h
@@ -37,11 +37,55 @@
 
 extern spinlock_t i8259A_lock;
 
+extern unsigned int cached_irq_mask;
+#define cached_master_mask	(cached_irq_mask)
+#define cached_slave_mask	(cached_irq_mask >> 8)
+
 extern void init_8259A(int auto_eoi);
 extern void enable_8259A_irq(unsigned int irq);
 extern void disable_8259A_irq(unsigned int irq);
 
 extern void init_i8259_irqs(void);
+#define CONFIG_NO_INTERRUPT_ACK
+#ifdef CONFIG_NO_INTERRUPT_ACK
+static inline int _byte_ffs(u8 word)
+{
+	int num = 0;
+	if ((word & 0xf) == 0) {
+		num += 4;
+		word >>= 4;
+	}
+	if ((word & 0x3) == 0) {
+		num += 2;
+		word >>= 2;
+	}
+	if ((word & 0x1) == 0)
+		num += 1;
+	return num;
+}
+
+static inline int read_irq(int port)
+{
+	int irq;
+	outb(0x0A, port);
+	if (port == PIC_MASTER_CMD) {
+		irq = inb(port) & ~cached_master_mask;
+	} else {
+		irq = inb(port) & ~cached_slave_mask;
+	}
+	if (irq == 0)
+		return -1;
+	else
+		return _byte_ffs(irq);
+}
+#else
+static inline int read_irq(int port)
+{
+	/* Perform an interrupt acknowledge cycle on controller 1. */
+	outb(0x0C, port);		/* prepare for poll */
+	return inb(port) & 7;
+}
+#endif
 
 /*
  * Do the traditional i8259 interrupt polling thing.  This is for the few
@@ -54,18 +98,16 @@ static inline int i8259_irq(void)
 
 	spin_lock(&i8259A_lock);
 
-	/* Perform an interrupt acknowledge cycle on controller 1. */
-	outb(0x0C, PIC_MASTER_CMD);		/* prepare for poll */
-	irq = inb(PIC_MASTER_CMD) & 7;
+	irq = read_irq(PIC_MASTER_CMD);
 	if (irq == PIC_CASCADE_IR) {
 		/*
 		 * Interrupt is cascaded so perform interrupt
 		 * acknowledge on controller 2.
 		 */
-		outb(0x0C, PIC_SLAVE_CMD);		/* prepare for poll */
-		irq = (inb(PIC_SLAVE_CMD) & 7) + 8;
-	}
+		irq = read_irq(PIC_SLAVE_CMD) + 8;
+	} 
 
+#ifndef CONFIG_NO_INTERRUPT_ACK
 	if (unlikely(irq == 7)) {
 		/*
 		 * This may be a spurious interrupt.
@@ -78,6 +120,11 @@ static inline int i8259_irq(void)
 		if(~inb(PIC_MASTER_ISR) & 0x80)
 			irq = -1;
 	}
+#else
+	if (cached_irq_mask & (1 << irq)) {
+		irq = -1;
+	}
+#endif
 
 	spin_unlock(&i8259A_lock);