Re: [PATCH] x86: Get irq for hpet timer

From: Kevin Hao
Date: Tue May 20 2008 - 05:04:31 EST


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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/