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


From: Max Filippov
Subject: Re: [Qemu-devel] [PATCH 3/3] target-xtensa: xtfpga: support noMMU cores
Date: Thu, 1 Oct 2015 23:13:26 +0300

On Thu, Oct 1, 2015 at 10:18 PM, Peter Crosthwaite
<address@hidden> wrote:
> On Thu, Oct 1, 2015 at 11:25 AM, Max Filippov <address@hidden> wrote:
>> On Thu, Oct 1, 2015 at 9:06 PM, Peter Crosthwaite
>> <address@hidden> wrote:
>>> What is your intended user command lines? E.g. how do I boot with
>>> ml605 no-mmu and then with mmu.
>>
>> '-M ml605 -cpu de108' will boot noMMU variant (de108 is not in the mainline 
>> yet,
>> can be seen in the https://github.com/OSLL/qemu-xtensa/commits/xtensa-cores),
>> '-M ml605 -cpu dc233c' will boot full MMU variant, as de108 doesn't
>> have full MMU
>> and dc233c does.
>
> So where I was going with this, is due to the way your devtools do
> memory maps, -cpu is the wrong switch altogether as what your tools
> call a "CPU" is different to what QEMU does. I am thinking:
>
> -M ml605 -global ml605.bitstream=xtensa-dc233c
>
> dc233c is a SoC that selects the correct xtensa CPU (either via
> property or an target-extensa CPU also named "dc233c"). When you set
> the bitstream property on the machine, it instantiates the correct SoC
> which in turn already knows the correct memory map and selects the CPU
> for you.
>
> When we have multi-arch working, we can then code-share the FPGA board
> definitions between arches e.g. petalogix-ml605 can be rewritten so
> that this works:
>
> qemu-system-multi -M ml605 -global ml605.bitstream=petalogix-mmu
> qemu-system-multi -M ml605 -global ml605.bitstream=xtensa-dc233c
>
> Names may needs some fine tuning.

I'm completely lost here. I have a problem at hand: noMMU cores
can't run on XTFPGA boards because of wrong device memory map.
The board is not meant to be used outside target-xtensa at all, and
even for target-xtensa it's just a demo board.

What problem do I solve by implementing it in the way you suggest?

-- 
Thanks.
-- Max



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