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

[Thomas Huth]

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