linux-kernel - Re: [PATCH] x86: Get irq for hpet timer

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Date:	Tue, 20 May 2008 17:03:39 +0800
From:	Kevin Hao <kexin.hao@...driver.com>
To:	Clemens Ladisch <clemens@...isch.de>
Cc:	venkatesh.pallipadi@...el.com, bob.picco@...com, mingo@...hat.com,
	tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Get irq for hpet timer

On Mon, 2008-05-19 at 18:10 +0200, Clemens Ladisch wrote:
> Kevin Hao wrote:
> > +	for (irq = find_first_bit(&cap, HPET_MAX_IRQ); irq < HPET_MAX_IRQ;
> > +		irq = find_next_bit(&cap, HPET_MAX_IRQ, 1 + irq)) {
> > +		if (request_irq(irq, hpet_interrupt, irq_flags,
> > +				devp->hd_name, (void *)devp))
> 
> This spams my log with interrupt sharing violations.  As long as we do
> not know that the interrupt slot is empty, we need IRQF_PROBE_SHARED
> here.

Ok, added.

> 
> Another problem: the interrupt controller doesn't get correctly
> initialized for some interrupt line that didn't already have some
> routing:
> | $ cat /proc/interrupts
> |            CPU0
> |   0:         63   IO-APIC-edge      timer
> |   1:         96   IO-APIC-edge      i8042
> |   2:          0    XT-PIC-XT        hpet2
> |   6:          3   IO-APIC-edge      floppy
> |   7:          0   IO-APIC-edge      parport0
> |   8:          3   IO-APIC-edge      rtc
> |   9:          0   IO-APIC-fasteoi   acpi
> | ...
> 
> Additionally, I vaguely remember that on X86, there is some funny stuff
> going on with interrupt lines 0, 2 and 8 which means that the interrupt
> number passed to request_irq() is not necessarily identical to the
> hardware interrupt line.
> 
> I don't know which of these problems is responsible, or if I'm totally
> wrong, but on my machine, interrupts from hpet2 do not arrive.
> 

We can simply skip these special IRQ. :-)
Does anyone has a better solution?

----
diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index 0fdc627..b04a15d 100644
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -390,6 +390,11 @@ static int hpet_timer_get_irq(struct hpet_dev *devp)
 	struct hpets *hpetp;
 	unsigned long cap, irq_flags;
 	int irq;
+	/*
+	 * skip IRQ0, IRQ2, IRQ8 because which is always used by some
+	 * legacy device
+	 */
+	unsigned long skip_irq = (1 << 0) | (1 << 2) | (1 << 8);
 
 	timer = devp->hd_timer;
 	hpet = devp->hd_hpet;
@@ -411,6 +416,9 @@ static int hpet_timer_get_irq(struct hpet_dev *devp)
 
 	cap = (readq(&timer->hpet_config) & Tn_INT_ROUTE_CAP_MASK)
 				 >> Tn_INT_ROUTE_CAP_SHIFT;
+	cap &= ~skip_irq;
+
+	irq_flags |= IRQF_PROBE_SHARED;
 
 	for (irq = find_first_bit(&cap, HPET_MAX_IRQ); irq < HPET_MAX_IRQ;
 		irq = find_next_bit(&cap, HPET_MAX_IRQ, 1 + irq)) {

---
Best Regards,
Kevin

> 
> Regards,
> Clemens
--
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