Enabling the IO-APIC on an Abit KT7A motherboard

Enabling the IO-APIC on an Abit KT7A motherboard

[Roger James]

I have been trying to get the IO-APIC on an Abit KT7A motherboard recognised
by the kernel (2.6.19.2). This is of course a single processor system. The
kernel has the CONFIG_X86_UP_APIC, CONFIG_X86_UP_IOAPIC,
CONFIG_X86_LOCAL_APIC, and CONFIG_X86_IOAPIC options set.

The reason I am trying this is in order to debug a system lock-up using the
nmi-watchdog facility. It looks like the lock up is caused by a hlt
instruction as the lapic based nmi-watchdog does not catch it.

I have put some debug in the various bits of code that are related to the
initialisation of the io-apic and its seems it is not being detected because
the bios does not supply an APIC table so..

acpi_table_parse(ACPI_APIC, acpi_parse_madt);

returns 0 and the IOAPIC is never found.

The only other route I can see where an IO-APIC might be enabled is via
get_smp_config but I don't think this get called on a single processor
system such as the KT7A.

Does anyone know how to force the io-apic to be found? Has anyone done this
before.

Here is a dump of the acpi tables returned by the BIOS.


DSDT @ 0x1fff3100
  0000: 44 53 44 54 be 24 00 00 01 25 56 54 38 33 37 31  DSDT.$...%VT8371
  0010: 41 57 52 44 41 43 50 49 00 10 00 00 4d 53 46 54  AWRDACPI....MSFT
  0020: 0c 00 00 01 10 19 5c 5f 50 52 5f 5b 83 11 5c 2e  ......\_PR_[..\.
  0030: 5f 50 52 5f 43 50 55 30 01 10 40 00 00 06 08 5c  _PR_CPU0..@....\
  0040: 5f 53 30 5f 12 06 04 00 00 00 00 08 5c 5f 53 31  _S0_........\_S1
  0050: 5f 12 0a 04 0a 04 0a 04 0a 04 0a 04 08 5c 5f 53  _............\_S
  0060: 34 5f 12 0a 04 0a 02 0a 02 0a 02 0a 02 08 5c 5f  4_............\_
  0070: 53 35 5f 12 0a 04 0a 02 0a 02 0a 02 0a 02 5b 80  S5_...........[.
  0080: 5c 44 45 42 47 01 0a 80 0a 01 5b 81 0c 5c 44 45  \DEBG.....[..\DE


......  loads of DSDT removed


  2410: 47 01 60 00 60 00 01 01 47 01 64 00 64 00 01 01  G.`.`...G.d.d...
  2420: 22 02 00 79 00 14 0e 5f 50 52 57 00 a4 12 06 02  "..y..._PRW.....
  2430: 0a 05 0a 05 14 2d 5c 2f 04 5f 53 42 5f 50 43 49  .....-\/._SB_PCI
  2440: 30 55 41 52 31 5f 50 52 57 00 a0 0d 4f 53 46 4c  0UAR1_PRW...OSFL
  2450: a4 12 06 02 0a 08 0a 04 a1 09 a4 12 06 02 0a 08  ................
  2460: 0a 08 14 2d 5c 2f 04 5f 53 42 5f 50 43 49 30 55  ...-\/._SB_PCI0U
  2470: 41 52 32 5f 50 52 57 00 a0 0d 4f 53 46 4c a4 12  AR2_PRW...OSFL..
  2480: 06 02 0a 08 0a 04 a1 09 a4 12 06 02 0a 08 0a 08  ................
  2490: 14 2d 5c 2f 04 5f 53 42 5f 50 43 49 30 45 43 50  .-\/._SB_PCI0ECP
  24a0: 31 5f 50 52 57 00 a0 0d 4f 53 46 4c a4 12 06 02  1_PRW...OSFL....
  24b0: 0a 08 0a 04 a1 09 a4 12 06 02 0a 08 0a 08        ..............

FACS @ 0x1fff0000
  0000: 46 41 43 53 40 00 00 00 00 00 00 00 00 00 00 00  FACS@...........
  0010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  0020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................

FACP @ 0x1fff3040
  0000: 46 41 43 50 84 00 00 00 02 bc 56 54 38 33 37 31  FACP......VT8371
  0010: 41 57 52 44 41 43 50 49 32 2e 30 30 41 57 52 44  AWRDACPI2.00AWRD
  0020: 00 00 00 00 00 00 ff 1f 00 31 ff 1f 00 00 09 00  .........1......
  0030: 2f 40 00 00 a1 a0 00 00 00 40 00 00 00 00 00 00  /@.......@......
  0040: f0 40 00 00 00 00 00 00 00 00 00 00 08 40 00 00  .@...........@..
  0050: 20 40 00 00 00 00 00 00 04 02 00 04 04 00 00 00   @..............
  0060: 5a 00 84 03 00 00 00 00 00 01 7d 7e 32 03 00 00  Z.........}~2...
  0070: 25 00 00 00 01 08 00 00 64 00 00 00 00 00 00 00  %.......d.......
  0080: fe 00 00 00                                      ....

RSDT @ 0x1fff3000
  0000: 52 53 44 54 28 00 00 00 01 56 56 54 38 33 37 31  RSDT(....VVT8371
  0010: 41 57 52 44 41 43 50 49 32 2e 30 30 41 57 52 44  AWRDACPI2.00AWRD
  0020: 00 00 00 00 40 30 ff 1f                          ....@0..

RSD PTR @ 0xf7770
  0000: 52 53 44 20 50 54 52 20 16 56 54 38 33 37 31 00  RSD PTR .VT8371.
  0010: 00 30 ff 1f                                      .0..


As you can see the RSDT only has one table pointer and that points at the
FACP table.

Am I flogging a dead horse with this?

Are there any routes other than ACPI where the IO-APIC might be enabled?

Is this the right list for this question?

Help!!

Roger

Re: Enabling the IO-APIC on an Abit KT7A motherboard

[Len Brown]

On Sunday 11 February 2007 12:11, Roger James wrote:
> I have been trying to get the IO-APIC on an Abit KT7A motherboard recognised
> by the kernel (2.6.19.2). This is of course a single processor system. The
> kernel has the CONFIG_X86_UP_APIC, CONFIG_X86_UP_IOAPIC,
> CONFIG_X86_LOCAL_APIC, and CONFIG_X86_IOAPIC options set.
> 
> The reason I am trying this is in order to debug a system lock-up using the
> nmi-watchdog facility. It looks like the lock up is caused by a hlt
> instruction as the lapic based nmi-watchdog does not catch it.
> 
> I have put some debug in the various bits of code that are related to the
> initialisation of the io-apic and its seems it is not being detected because
> the bios does not supply an APIC table so..
> 
> acpi_table_parse(ACPI_APIC, acpi_parse_madt);
> 
> returns 0 and the IOAPIC is never found.

Check if there is a BIOS SETUP option to enable the IO-APIC.

No, you can't manufacture ACPI support for an IOAPIC on a system
where the BIOS doesn't tell the OS about it via ACPI tables.

Alternatively, you can boot with "acpi=off", and if the board has MPS,
that will enable the IOAPIC (assuming the HW has one).

If neither of these work, it means your board vendor intentionally
did not enable the IOAPIC.

I don't really understand your motivation for enabling the IOAPIC above,
but it is true that if it is supported and works, you generally want to
take advantage of it to reduce interrupt sharing.

cheers,
-Len