Re: [PATCH] hw/ppc: Deprecate the ref405ep and taihu machines and the 405 CPU models

[Thomas Huth <thuth@redhat.com>]

On 01/10/2021 14.46, Peter Maydell wrote:
> On Fri, 1 Oct 2021 at 13:22, Thomas Huth <thuth@redhat.com> wrote:
>>
>> These machines need a firmware image called 'ppc405_rom.bin', and nobody
>> seems to have such a firmware image left for testing, so the machines are
>> currently unusable. There used to be support in U-Boot, but it has been
>> removed a couple of year ago already.
>> Thus let's mark these boards and the 405 CPU as deprecated now, so that we
>> could remove them in a couple of releases (unless somebody speaks up and
>> says that these are still usefull for them).
>>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>   docs/about/deprecated.rst | 15 +++++++++++++++
>>   hw/ppc/ppc405_boards.c    |  2 ++
>>   2 files changed, 17 insertions(+)
>>
>> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
>> index 2f7db9a98d..27c03ef624 100644
>> --- a/docs/about/deprecated.rst
>> +++ b/docs/about/deprecated.rst
>> @@ -238,6 +238,11 @@ The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated
>>   (the ISA has never been upstreamed to a compiler toolchain). Therefore
>>   this CPU is also deprecated.
>>
>> +PPC 405 CPU models (since 6.2)
>> +''''''''''''''''''''''''''''''
>> +
>> +The related boards ``ref405ep`` and ``taihu`` are marked as deprecated, too.
>> +
> 
> What is this "too" a reference to? The immediately preceding section
> in the document is about the MIPS I7200 CPU model.

It was meant as a reference to the machines below. I'll try to rephrase in v2.
(As far as I can see, the 405 can only be used on these boards, it does not 
seem to be possible to use these CPU types on other boards)

> The not-being-deprecated sam460ex board also uses the ppc405 CPU
> I think, so I don't think we can drop the CPU models.

No, that board uses a 460exb CPU which is a slightly different kind of 
embedded PPC CPU, as far as I know.

>>   QEMU API (QAPI) events
>>   ----------------------
>> @@ -258,6 +263,16 @@ This machine is deprecated because we have enough AST2500 based OpenPOWER
>>   machines. It can be easily replaced by the ``witherspoon-bmc`` or the
>>   ``romulus-bmc`` machines.
>>
>> +``ref405ep`` and ``taihu`` machines (since 6.2)
>> +'''''''''''''''''''''''''''''''''''''''''''''''
>> +
>> +These machines need a firmware image called 'ppc405_rom.bin', and nobody seems
>> +to have a working copy of such a firmware image anymore. `Support in U-Boot
> 
> "any more".
> 
>> +<https://gitlab.com/qemu-project/u-boot/-/commit/98f705c9cefdfdba62c069>`__
>> +has been removed a couple of years ago, too, so it is very unlikely that
>> +anybody is still using this code at all.
> 
> (I'm not sure whether anybody ever actually successfully booted a
> u-boot binary on QEMU's taihu/ref405ep boards.)

Me neither. Maybe I should rather drop that reference in v2...
but I still wonder where that "ppc405_rom.bin" originally came from...

>>   Backend options
>>   ---------------
>>
>> diff --git a/hw/ppc/ppc405_boards.c b/hw/ppc/ppc405_boards.c
>> index 972a7a4a3e..1578c0dac8 100644
>> --- a/hw/ppc/ppc405_boards.c
>> +++ b/hw/ppc/ppc405_boards.c
>> @@ -317,6 +317,7 @@ static void ref405ep_class_init(ObjectClass *oc, void *data)
>>       mc->init = ref405ep_init;
>>       mc->default_ram_size = 0x08000000;
>>       mc->default_ram_id = "ef405ep.ram";
>> +    mc->deprecation_reason = "ppc405 CPU is deprecated";
>>   }
>>
>>   static const TypeInfo ref405ep_type = {
>> @@ -547,6 +548,7 @@ static void taihu_class_init(ObjectClass *oc, void *data)
>>       mc->init = taihu_405ep_init;
>>       mc->default_ram_size = 0x08000000;
>>       mc->default_ram_id = "taihu_405ep.ram";
>> +    mc->deprecation_reason = "ppc405 CPU is deprecated";
>>   }
> 
> We're not deprecating the machine types because we're deprecating
> the CPU types. We're deprecating them because we believe that
> nobody's using them.

Ok, I'll try to come up with a different text instead.

  Thomas