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SubjectRe: RTC Chip and IRQ8 on 2.6.9
On Sat, 13 Nov 2004, Randy.Dunlap wrote:

> linux-os wrote:
>>
>> I must use the RTC and IRQ8 in a driver being ported from
>> 2.4.20 to 2.6.9. When I attempt request_irq(8,...), it
>> returns -EBUSY. I have disabled everything in .config
>> that has "RTC" in it.
>>
>> The RTC interrupt is used to precisely time the sequencing
>> of a precision A/D converter. It is mandatory that I use
>> it because the precise interval is essential for its
>> IIR filter that produces 20 bits of resolution from a
>> 16 bit A/D.
>>
>> CPU0
>> 0: 60563767 IO-APIC-edge timer
>> 1: 57096 IO-APIC-edge i8042
>> 8: 1 IO-APIC-edge rtc
>> 9: 0 IO-APIC-level acpi
>> 12: 66 IO-APIC-edge i8042
>> 14: 112322 IO-APIC-edge ide0
>> 16: 0 IO-APIC-level uhci_hcd, uhci_hcd
>> 18: 640 IO-APIC-level libata, uhci_hcd, Analogic Corp DLB
>> 19: 0 IO-APIC-level uhci_hcd
>> 20: 4894484 IO-APIC-level eth0
>> 21: 110543 IO-APIC-level aic7xxx
>> 23: 0 IO-APIC-level ehci_hcd
>> NMI: 0 LOC: 60565403 ERR: 0
>> MIS: 0
>>
>> This stuff works fine in 2.4.22 and, in fact, I'm the guy
>> that added the global rtc_lock so that this very driver
>> could run without interfering with anybody. Now, some code,
>> somewhere (not in a module), has allocated the interrupt
>> and generated exactly 1 interrupt. The kernel won't let
>> me use that interrupt!
>>
>> How do I undo this so I can use my hardware on my machine?
>
> I happen to be running a 2.6.9-rc1 kernel right now, with
> an IO APIC (P4 UP), and no RTC support built into it,
> and /proc/interrupts show IRQ 8 empty/unassigned:
>
> CPU0
> 0: 777037582 IO-APIC-edge timer
> 1: 185323 IO-APIC-edge i8042
> 7: 0 IO-APIC-edge parport0
> 9: 0 IO-APIC-level acpi
> 12: 2838473 IO-APIC-edge i8042
> 14: 1197859 IO-APIC-edge ide0
> 15: 42 IO-APIC-edge ide1
> 17: 49 IO-APIC-level aic7xxx, ohci_hcd
> 19: 0 IO-APIC-level uhci_hcd
> 21: 197 IO-APIC-level ohci1394, ohci_hcd, ohci_hcd, ohci_hcd,
> ohci_hc
> d, ohci_hcd
> 22: 832350 IO-APIC-level ehci_hcd, eth0
> 23: 16387 IO-APIC-level es1371, uhci_hcd
> NMI: 0
> LOC: 776994543
> ERR: 0
> MIS: 0
>
>
> Perhaps your .config and a simple test case would help.

Yep. The .config needed to set up RTC as a module so that
I could unload it (seriously) in order to free it up.

Otherwise the built-in RTC software grabbed IRQ8 even though
it never used it.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.9 on an i686 machine (5537.79 BogoMips).
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