Re: [OpenBIOS] sbus slot probing

[Blue Swirl]

On Fri, Aug 19, 2011 at 8:44 PM, Mark Cave-Ayland
 wrote:
> On 15/08/11 16:01, Bob Breuer wrote:
> > Here's a preliminary patch for sbus slot probing.
>
> Great work indeed :)
> > This can be used for the preliminary dbri device patch, see my dbri-pre1
> > branch at github: https://github.com/breuerr/qemu/tree/dbri-pre1
> > That branch also has a rewritten fcode rom to avoid the use of the
> > obsolete intr forth word.  Use the SS-20 machine to get the dbri device.
> >
> > Todo:
> >   non-faulting reads so that an empty slot can be probed
> >   extend to probe other (all?) slots as well
> >   only add the slot E range for SS-20, but not SS-10
> >
> > Is there any existing code for sparc32 which does a non-faulting read?  It
> > looks like even cpeek doesn't try to catch any faults.
>
> Not that I know of. It looks as if there may be some work that needs to be
> done in qemu in order for this to happen as per the comment in
> hw/sun4m_iommu.c:
>
> case IOMMU_ARBEN:
>        // XXX implement SBus probing: fault when reading unmapped
>        // addresses, fault cause and address stored to MMU/IOMMU
>        s->regs[saddr] = (val & IOMMU_ARBEN_MASK) | IOMMU_MID;
>        break;
>
> I have a feeling that qemu invokes a known trap for unmapped memory, so it
> could be that given we know the SBus range we could just assume that any
> traps occurring during a read to that range is a failed probe?

The documentation is pretty weak in this area, the comments above are
just my guesses.
> > Bob
> > Index: drivers/sbus.c
> >
> > --- drivers/sbus.c      (revision 1046)
> > +++ drivers/sbus.c      (working copy)
> > @@ -451,11 +451,36 @@
> >  static void
> >  sbus_probe_slot_ss10(unsigned int slot, uint64_t base)
> >  {
> > ucell fcode;
> > unsigned char start;
> >
> > // OpenBIOS and Qemu don't know how to do Sbus probing
> >      switch(slot) {
> >      case 2: // SUNW,tcx
> >          ob_tcx_init(slot, "/iommu/sbus/SUNW,tcx");
> >          break;
> > case 0xe: // dbri
> > fcode = ofmem_map_io(base, 0x1000);
> > // TODO: non-faulting read
> > start = *(unsigned char*)fcode;
> > if (start == 0xfd || start == 0xf1) {
>
> See is_fcode() in libopenbios/fcode_load.c.
> > push_str("/iommu/sbus");
> > fword("select-dev");
> > fword("new-device");
> > push_str(NULL);
> > PUSH(0);    // offset
> > PUSH(slot); // space
> > push_str("encode-unit");
> > fword("$call-parent");
> > fword("set-args");
> > PUSH(fcode);
> > PUSH(1);
> > fword("byte-load");
> > fword("finish-device");
> > fword("unselect-dev");
> > }
> > ofmem_unmap(fcode, 0x1000);
> > break;
> >
> > case 0xf: // le, esp, bpp, power-management
> >          ob_macio_init(slot, base, 0);
> >          // Power management (APC) XXX should not exist
> > @@ -534,6 +559,7 @@
> >      { 1, 0, 0xe10000000ULL, 0x10000000,},
> >      { 2, 0, 0xe20000000ULL, 0x10000000,},
> >      { 3, 0, 0xe30000000ULL, 0x10000000,},
> > [0xe] = { 0xe, 0, 0xee0000000ULL, 0x10000000,},
> >
> > [0xf] = { 0xf, 0, 0xef0000000ULL, 0x10000000,},
> >  };
>
> The only other thing I'd like to see, as you mention, is the probe moved
> into a separate function which can be called from the appropriate _init()
> functions. I'd be interested to follow the discussion related to handling
> the various traps that occur during a fault access on this thread as you
> progress.
>
> ATB,
>
> Mark.
>
> Sirius Labs: http://www.siriusit.co.uk/labs