Re: [RFC] PCI bridge driver rewrite

From: Adam Belay (abelay_at_novell.com)
Date: 03/01/05

  • Next message: Dave Hansen: "Re: [PATCH 3/5] abstract discontigmem setup" 
    To: Jesse Barnes <jbarnes@sgi.com>
Date:	Mon, 28 Feb 2005 18:27:47 -0500

    On Thu, 2005-02-24 at 15:02 -0800, Jesse Barnes wrote:
    > On Wednesday, February 23, 2005 11:03 pm, Adam Belay wrote:
    >
    > > > Jesse can comment on the specific support needed for multiple legacy IO
    > > > spaces.
    > >
    > > That would be great. Most of my experience has been with only a couple
    > > legacy IO port ranges passing through the bridge.
    >
    > Well, I'll give you one, somewhat perverse, example. On SGI sn2 machines,
    > each host<->pci bridge (either xio<->pci or numalink<->pci) has two pci
    > busses and some additional host bus ports. The bridges are capable of
    > generating low address bus cycles on both busses simultaneously, so we can do
    > ISA memory access and legacy port I/O on every bus in the system at the same
    > time.
    >
    > The main host chipset has no notion of VGA or legacy routing though, so doing
    > a port access to say 0x3c8 is ambiguous--we need a bus to target (though the
    > platform code could provide a 'default' bus for such accesses to go to, this
    > may be what VGA or legacy routing means for us under your scheme). Likewise,
    > accessing ISA memory space like 0xa0000 needs a bus to target.
    >
    > It would be nice if this sort of thing was taken into account in your new
    > model, so that for example we could have the vgacon driver talking to
    > multiple different VGA cards at the same time.
    >
    > Thanks,
    > Jesse

    How can we specify which bus to target? Also is the legacy IO space
    mapped to IO Memory on the other side of the bridge?

    Thanks,
    Adam

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  • Next message: Dave Hansen: "Re: [PATCH 3/5] abstract discontigmem setup"

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