[OpenBIOS] sbus slot probing

[Blue Swirl]

On Fri, Aug 19, 2011 at 8:44 PM, Mark Cave-Ayland
<mark.cave-ayland at siriusit.co.uk> 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.
>
> --
> Mark Cave-Ayland - Senior Technical Architect
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>
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>
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