From: Jos Hulzink <josh@stack.nl>
To: "STK" <stk@nerim.net>, "'linux-kernel'" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] How to fix MPS 1.4 + ACPI behaviour ?
Date: Tue, 13 May 2003 10:54:25 +0200
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Cc: "'Zwane Mwaikambo'" <zwane@linuxpower.ca>
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Hi,

As you can see below, current ACPI implementation concludes it has to use the 
PIC, before it finds the PRT. No occurences of PRT in dmesg before this one.

vvvv
ACPI: Using PIC for interrupt routing
^^^^
ACPI: PCI Interrupt Link [LNKA] (IRQs 3 4 *5 6 7 9 10 11 12 14 15)
ACPI: PCI Interrupt Link [LNKB] (IRQs 3 4 5 6 *7 9 10 11 12 14 15)
ACPI: PCI Interrupt Link [LNKC] (IRQs 3 4 5 6 7 9 *10 11 12 14 15)
ACPI: PCI Interrupt Link [LNKD] (IRQs 3 4 5 6 7 9 10 *11 12 14 15)
ACPI: PCI Root Bridge [PCI0] (00:00)
PCI: Probing PCI hardware (bus 00)
vvvv
ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT]
^^^^

Jos

On Monday 12 May 2003 23:29, STK wrote:
> For me the linux kernel should invoke the _PIC method with the right
> parameter.
>
> Look at the specification Section
>
> << ================ Start ================
> 5.8.1 _PIC Method
> The \_PIC optional method is to report to the BIOS the current interrupt
> model used by the OS. This
> control method returns nothing. The argument passed into the method
> signifies the interrupt model OSPM
> has chosen, PIC mode, APIC mode, or SAPIC mode. Notice that calling this
> method is optional for OSPM.
> If the method is never called, the BIOS must assume PIC mode. It is
> important that the BIOS save the value
> passed in by OSPM for later use during wake operations.
> _PIC(x):
> _PIC(0) => PIC Mode
> _PIC(1) => APIC Mode
> _PIC(2) => SAPIC Mode
> _PIC(3-n) => Reserved
>
> ==================== End ====================>
>
> ==> No MADT table, so ACPI sets up the APIC in PIC mode (which I wonder
> wether correct, but ok)
> For me the kernel should invoke the _PIC method with the right
> parameter, in this case the ACPI module will receive the right table
> during the _PRT
>
> Bios ASL code:
>                 Method(_PRT)
>                 {
>                 If(\PICF) <== internal variable set by _PIC
>                 {
>                 	==> Returning APIC Mode
>                 	Return(APIC)
>                 }
>                 Else
>                 {
>                 	==> Returning PIC Mode
>                 	Return(PICM)
>                 }
> 			}
>
> Regards,
>
> Yann
>
>
> -----Original Message-----
> From: Jos Hulzink [mailto:josh@stack.nl]
> Sent: lundi 12 mai 2003 22:51
> To: STK; 'linux-kernel'
> Cc: 'Zwane Mwaikambo'
> Subject: Re: [RFC] How to fix MPS 1.4 + ACPI behaviour ?
>
> On Monday 12 May 2003 22:40, STK wrote:
> > Hi,
> >
> > If no Multiple APIC Description Table (MADT) is described, in this
> > case the _PIC method can be used to tell the bios to return the right
> > table (PIC or APIC routing table).
> >
> > In this case, if the MPS table describes matches the ACPI APIC table
> > (this is the case, because the ACPI APIC table is built from the MPS
> > table), you do not need to remap all IRQs.
>
> So, it's more or less a bug in the ACPI code that should do some things
> when
> no MADT is dectected ? Or do I understand you wrong ?
>
> Jos

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