Re: [SeaBIOS] [PATCH RFC] acpi: add ssdt for cpi hotplug

[Michael S. Tsirkin]

On Tue, Nov 01, 2011 at 06:59:01PM -0400, Kevin O'Connor wrote:
> On Tue, Nov 01, 2011 at 09:11:40PM +0200, Michael S. Tsirkin wrote:
> > So here's the plan: move all hotplug handling out
> > to ssdt, this way it'll keep working even with a
> > user-supplied dsdt. Next step we can patch
> > this ssdt at runtime.
> >
> > There's little point in this change alone, so posting as RFC,
> > will repost with the patching part when it's ready,
> > posting now to present opportunity for early feedback.
>
> [...]
> >        OperationRegion(PCST, SystemIO, 0xae00, 0x08)
> >        Field (PCST, DWordAcc, NoLock, WriteAsZeros)
> >        {
> >            PCIU, 32,
> >            PCID, 32,
> >        }
> >        OperationRegion(SEJ, SystemIO, 0xae08, 0x04)
> >        Field (SEJ, DWordAcc, NoLock, WriteAsZeros)
> >        {
> >            B0EJ, 32,
> >        }
> >        OperationRegion(RMVC, SystemIO, 0xae0c, 0x04)
> >        Field(RMVC, DWordAcc, NoLock, WriteAsZeros)
> >        {
> >            PCRM, 32,
> >        }
>
> [...]
> > Scope(_SB.PCI0) {
> >    /* Methods called by bulk generated PCI devices below */
> >    Method (PRMV, 1, NotSerialized) {
> >        // _RMV method - check if device can be removed
> >        If (And(\_SB.PCI0.PCRM, ShiftLeft(1, Arg0))) {
> >            Return (0x1)
> >        }
> >        Return (0x0)
> >    }
>
> [...]
> >    /* Methods called by bulk generated hotplug devices below */
> >    Method (PCEJ, 1, NotSerialized) {
> >        // _EJ0 method - eject callback
> >        Store(ShiftLeft(1, Arg0), B0EJ)
> >        Return (0x0)
> >    }
>
> [...]
> >    /* PCI hotplug notify method */
> >    Method(PCNF, 0) {
> >        // Local0 = iterator
> >        Store (Zero, Local0)
> >        While (LLess(Local0, 31)) {
> >            Increment(Local0)
> >            If (And(PCIU, ShiftLeft(1, Local0))) {
> >                PCNT(Local0, 1)
> >            }
> >            If (And(PCID, ShiftLeft(1, Local0))) {
> >                PCNT(Local0, 3)
> >            }
> >        }
> >        Return(One)
> >    }
>
> [...]
> >    Method(_L01) {
> >        // PCI hotplug event
> >        Return(\_SB.PCI0.PCNF())
> >    }
>
> Can we leave these parts in the DSDT and only move the bulk generated
> stuff to the SSDT?
>
> -Kevin

They can, but I thought one of the reasons we do the split
is to make it possible for users to supply their own DSDT?
If so creating calls from SSDT into DSDT would make this very fragile.

Two other things to note:
1. I didn't find a way to avoid such a dependency completely:
   there is a requirement for the DSDT to call the root bus PCI0.
2. The RMV will be removed from asl and move into BIOS
   for runtime patching.

What do you think?