Re: [Qemu-devel] [PATCH 3/3] target-xtensa: xtfpga: support noMMU cores

[Peter Crosthwaite]

On Wed, Sep 30, 2015 at 3:42 PM, Max Filippov <address@hidden> wrote:
> On Thu, Oct 1, 2015 at 1:23 AM, Peter Crosthwaite
> <address@hidden> wrote:
>> On Wed, Sep 30, 2015 at 3:07 PM, Max Filippov <address@hidden> wrote:
>>> On Thu, Oct 1, 2015 at 12:02 AM, Peter Crosthwaite
>>> <address@hidden> wrote:
>>>> Which makes MMU vs noMMU a board level property, not a CPU property.
>>>> It should appear in QEMU as such.
>>>
>>> Ok, one last try: can this property be queried from the selected CPU
>>> and passed to SoC initialization code?
>>
>> No, what I am trying to say is go the other way round. The property is
>> on the SoC, and it is used to select the CPU type.
>
> This is not what happens in reality. In reality the MMU type is the
> CPU property.
> A set of CPU properties comes from the outside along with the CPU name, and
> that's the only possible set of properties for this name.
> XTFPGA bitstream build scripts lay out its address space based on MMU
> type of the selected CPU.
>
> So let's make XTFPGA an SoC with a property that selects its address space
> layout. The machine (lx60/lx200/ml605/kc705) is configured with a CPU,

So lx60/lx200 sound like isolated FPGA chips (Virtex 4 lx60?) while
ml605/kc705 are commonly available fully-featured FPGA dev boards.

Is lx60 short for a particular board featuring this part or is it more abstract?

> it
> queries MMU type from it and instantiates XTFPGA SoC with proper address
> space. That seems to be closest to what happens in reality.
>

What is your intended user command lines? E.g. how do I boot with
ml605 no-mmu and then with mmu.

Regards,
Peter

> --
> Thanks.
> -- Max