Re: Deprecate the ppc405 boards in QEMU? (was: [PATCH v3 4/7] MAINTAINERS: Orphan obscure ppc platforms)

[Luis Machado <luis.machado@linaro.org>]

On 10/20/21 10:16 AM, LEROY Christophe wrote:
> 
> 
> Le 20/10/2021 à 14:43, Cédric Le Goater a écrit :
>> On 10/20/21 13:42, BALATON Zoltan wrote:
>>> On Wed, 20 Oct 2021, Philippe Mathieu-Daudé wrote:
>>>> On 10/5/21 14:29, Thomas Huth wrote:
>>>>> On 05/10/2021 14.20, BALATON Zoltan wrote:
>>>>>> On Tue, 5 Oct 2021, Cédric Le Goater wrote:
>>>>>>> On 10/5/21 08:18, Alexey Kardashevskiy wrote:
>>>>>>>> On 05/10/2021 15:44, Christophe Leroy wrote:
>>>>>>>>> Le 05/10/2021 à 02:48, David Gibson a écrit :
>>>>>>>>>> On Fri, Oct 01, 2021 at 04:18:49PM +0200, Thomas Huth wrote:
>>>>>>>>>>> On 01/10/2021 15.04, Christophe Leroy wrote:
>>>>>>>>>>>> Le 01/10/2021 à 14:04, Thomas Huth a écrit :
>>>>>>>>>>>>> On 01/10/2021 13.12, Peter Maydell wrote:
>>>>>>>>>>>>>> On Fri, 1 Oct 2021 at 10:43, Thomas Huth <thuth@redhat.com>
>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>> Nevertheless, as long as nobody has a hint where to find that
>>>>>>>>>>>>>>> ppc405_rom.bin, I think both boards are pretty useless in
>>>>>>>>>>>>>>> QEMU (as far as I
>>>>>>>>>>>>>>> can see, they do not work without the bios at all, so it's
>>>>>>>>>>>>>>> also not possible
>>>>>>>>>>>>>>> to use a Linux image with the "-kernel" CLI option directly).
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> It is at least in theory possible to run bare-metal code on
>>>>>>>>>>>>>> either board, by passing either a pflash or a bios argument.
>>>>>>>>>>>>>
>>>>>>>>>>>>> True. I did some more research, and seems like there was once
>>>>>>>>>>>>> support for those boards in u-boot, but it got removed there a
>>>>>>>>>>>>> couple of years ago already:
>>>>>>>>>>>>>
>>>>>>>>>>>>> https://gitlab.com/qemu-project/u-boot/-/commit/98f705c9cefdf
>>>>>>>>>>>>>
>>>>>>>>>>>>> https://gitlab.com/qemu-project/u-boot/-/commit/b147ff2f37d5b
>>>>>>>>>>>>>
>>>>>>>>>>>>> https://gitlab.com/qemu-project/u-boot/-/commit/7514037bcdc37
>>>>>>>>>>>>>
>>>>>>>>>>>>>> But I agree that there seem to be no signs of anybody actually
>>>>>>>>>>>>>> successfully using these boards for anything, so we should
>>>>>>>>>>>>>> deprecate-and-delete them.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Yes, let's mark them as deprecated now ... if someone still
>>>>>>>>>>>>> uses
>>>>>>>>>>>>> them and speaks up, we can still revert the deprecation again.
>>>>>>>>>>>>
>>>>>>>>>>>> I really would like to be able to use them to validate Linux
>>>>>>>>>>>> Kernel
>>>>>>>>>>>> changes, hence looking for that missing BIOS.
>>>>>>>>>>>>
>>>>>>>>>>>> If we remove ppc405 from QEMU, we won't be able to do any
>>>>>>>>>>>> regression
>>>>>>>>>>>> tests of Linux Kernel on those processors.
>>>>>>>>>>>
>>>>>>>>>>> If you/someone managed to compile an old version of u-boot for
>>>>>>>>>>> one of these
>>>>>>>>>>> two boards, so that we would finally have something for
>>>>>>>>>>> regression testing,
>>>>>>>>>>> we can of course also keep the boards in QEMU...
>>>>>>>>>>
>>>>>>>>>> I can see that it would be usefor for some cases, but unless
>>>>>>>>>> someone
>>>>>>>>>> volunteers to track down the necessary firmware and look after
>>>>>>>>>> it, I
>>>>>>>>>> think we do need to deprecate it - I certainly don't have the
>>>>>>>>>> capacity
>>>>>>>>>> to look into this.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I will look at it, please allow me a few weeks though.
>>>>>>>>
>>>>>>>> Well, building it was not hard but now I'd like to know what board
>>>>>>>> QEMU actually emulates, there are way too many codenames and PVRs.
>>>>>>>
>>>>>>> yes. We should try to reduce the list below. Deprecating embedded
>>>>>>> machines
>>>>>>> is one way.
>>>>>>
>>>>>> Why should we reduce that list? It's good to have different cpu
>>>>>> options when one wants to test code for different PPC versions (maybe
>>>>>> also in user mode) or just to have a quick list of these at one place.
>>>>>
>>>>> I think there are many CPUs in that list which cannot be used with any
>>>>> board, some of them might be also in a very incomplete state. So
>>>>> presenting such a big list to the users is confusing and might create
>>>>> wrong expectations. It would be good to remove at least the CPUs which
>>>>> are really completely useless.
>>>>
>>>> Maybe only remove some from system emulation but keep all of them
>>>> in user emulation?
>>>
>>> Or keep them all but mark those that are not tested/may be incomplete?
>>> So the used can see what is expected to work and what may need to be
>>> fixed. That way somebody may try and fix it whereas if it's not there
>>> they are unlikely to try to add it.
>>
>>
>> The bamboo machine with 440 CPUs is booting with the latest kernel
>> and we have an acceptance test for it now, thanks to Thomas. There
>> is not much effort in keeping them in a working state until someone
>> volunteers. Hopefully, Christophe is making sure that we are not
>> breaking anything with Linux support.
>>
>> The 405 machine are still close to deprecation I think. We are still
>> struggling to boot one with mainline Linux, using uboot provided by
>> Thomas which skips SDRAM init. It is not clear to me if u-boot is
>> strictly necessary. It depends if Linux relies on it to do some
>> pre-initialization of HW. I guess once we find a good DTS for it, or
>> not, we can take a decision.
>>
> 
> I now have a hacked configuration booting linux with the hotfoot DTS and
> the kernel is booting up to starting /init
> 
> Then it is faulting forever taking a DSI for write protection. The
> problem is now likely in Linux and I'm investigating it, but I'm having
> problem with GDB (7.8.1), I'm hitting the bug
> https://sourceware.org/bugzilla/show_bug.cgi?id=17700
> 
> And GDB 11.1 coredumps while reading vmlinux's symbols
> 
> Hopefully I'll find a GDB version between 7.8 and 11 that works.
> 

Just to confirm, you're not really having problems with the ARM port of 
GDB, right? It is a 32-bit PowerPC one. The bug you pointed out is only 
a reference to a similar one for PowerPC?