Re: [Qemu-ppc] [PATCH 2/2] m48t59: add mem_base value to m48t59_init_isa()

[Artyom Tarasenko]

On Mon, Jan 19, 2015 at 4:31 PM, Paolo Bonzini <address@hidden> wrote:
>
>
> On 19/01/2015 16:22, Artyom Tarasenko wrote:
>>>> >>
>>>> >> On physical machines it's EBus, which is pretty much like 8-bit ISA.
>>>> >> So, I think modelling it as ISA is closer to to the reality.
>>>> >> But out of curiosity, would it be possible to have a sysbus device
>>>> >> somewhere in a middle of PCI space? [...]
>>> >
>>> > Why would you want to use a SysBusDevice in the first place?
>> Ask Paolo. :-) For me it's only important to have a MMIO device in the
>> proper address range.
>
> The reason I asked is simply because ISA devices never do MMIO (apart
> for the VGA window).

You mean in the QEMU world? At least physical SCSI and Ethernet
adapters had a MMIO space for the onboard ROM.

>>> > I previously discussed with Mark that it should be an EBusDevice, not an
>>> > ISADevice or SysBusDevice.
>> Interesting. I can't find this discussion in the list archive. Do you 
>> suggest to
>> create EBusDevices for all ISA devices (serial, parallel, keyboard,
>> floppy) used in sun4u, or only for m48t59?
>> What would be the advantage of using EBusDevice over ISADevice?
>
> Is there a description of EBus and the sun4u memory map somewhere?

I could find only sparse pieces. "Uniprocessor System Controller
User's Manual" (805-0170.pdf) has some brief description, it's also
mentioned in the STP2223BGA  and STP2200ABGA data sheets.

> Is there an "EBus bridge" PCI device similar to the PCI-to-ISA bridge?

As physical devices there are integrated SBus-to-EBus and PCI-to-EBus bridges.

But actually I may have been wrong about NVRAM always sitting on the
EBus: looking at the page 28 of "UltraSPARC™-IIi User's Manual"
(805-0087.pdf), I see that NVRAM, Serial and other controllers reside
in a "PC compatible SuperIO" chip which sits on a PCI bus.

Artyom

-- 
Regards,
Artyom Tarasenko

SPARC and PPC PReP under qemu blog: http://tyom.blogspot.com/search/label/qemu