Re: PCI bus numbering and orphaned devices

From: John-Mark Gurney (gurney_j_at_efn.org)
Date: 06/11/03

  • Next message: Kris Kennaway: "Re: [solved] buildworld error" 
    Date: Tue, 10 Jun 2003 17:38:28 -0700
To: ticso@cicely.de

    Bernd Walter wrote this message on Wed, Jun 11, 2003 at 01:16 +0200:
    > On Tue, Jun 10, 2003 at 03:34:36PM -0700, John-Mark Gurney wrote:
    > > So, the question is, does other arch's do something nasty like this
    > > too? Should I change the check to just do ofw_pci_find_node? Is this
    > > why pciconf -r is returning 0xffffffff when reading the ebus and firewire
    > > parts of the SME2300BGA? Simply because it isn't in the ofw tree?
    >
    > Possible - in fact I was very surprised that a disabled device was not
    > readable on some registers.
    > We have a similar situation on alpha, where we get traps for reading non
    > available devices.
    > It's handled in that we tell the system to expect traps before accessing
    > registers.
    > This is done by reading with the badaddr function, which sets a flag for
    > our trap handler so it can continue in case the device doesn't exist.
    > badaddr() returns a flags which tells if reading was successfull.
    >
    > > I don't have any data sheets or the PCI spec, so making heads or tails
    > > of this is going be hard.
    >
    > It's OK to get errors when reading locations that aren't available.
    > Some chipsets nerver trap, others only trap for type2 access (behind
    > Bridges) and some always trap.

    It's amazing what reading the specs for a CPU can do. The US-IIi
    specificly has a section on this. 16.2.1 Probing PCI durning boot
    using deferred errors.

    Guess I'll be looking at implementing that. Then we can get ride
    of that ickyness in the psycho_read_config function. 

    -- 
  John-Mark Gurney				Voice: +1 415 225 5579
     "All that I will do, has been done, All that I have, has not."
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