Re: [PATCH] ARM: Delete ARM11MPCore (ARM11 ARMv6K SMP) support

["Arnd Bergmann" <arnd@arndb.de>]

On Tue, Dec 5, 2023, at 10:47, Linus Walleij wrote:
> On Tue, Dec 5, 2023 at 8:00 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
>>  static const struct of_device_id realview_scu_match[] = {
>> -       { .compatible = "arm,arm11mp-scu", },
>>         { .compatible = "arm,cortex-a9-scu", },
>>         { .compatible = "arm,cortex-a5-scu", },
>>         { }
>>
>> I see that the arm,arm11mp-scu device is provided by
>> arm-realview-eb-mp.dtsi, which in turn gets included
>> by both arm-realview-eb-11mp.dts and arm-realview-eb-a9mp.dts,
>> so the Cortex-A9 dtb ends up with the wrong compatible
>> string at the moment.
>
> Aha I need to make a separate DTS patch for that.
>
> As stated in the commit message I don't know if RealView EB
> is working very well on real hardware, I have only ever tested
> it in QEMU.

I think that is true for most users, and I see that
the Cortex-A9 variant of RealView EB doesn't even
have a separate qemu model other than possibly
"qemu-system-arm -M realview-eb-mpcore -cpu cortex-a9".

In this case, the easiest solution is probably to
kill off CONFIG_REALVIEW_EB_A9MP and its dts file
as well, since that is even less likely to have any
users.

>> The driver doesn't care either way, and we can easily
>> change the dtsi file use the Cortex-A9 compatibles
>> later, but I think we probably want to leave the
>> platsmp code to match the old string as well for
>> compatibility with old dtb files.
>
> The patch deletes the support for RealView EB ARM11MPCore
> Kconfig as well so it should go I think? Or am I missing
> something?

I was talking about EB_A9MP, not EB_ARM11MP here.

> The Marvell MMP3 is also defining the "arm,arm11mp-scu"
> but it's not using it for anything so I think it's just some bogus
> copypaste error (Lubomir can maybe fill in) and should have its
> own compatible.

Right, my impression is that these bits of MMP3
are all copied from realview.

> BTW is the Marvell PJ4B a descendant of the XScale PXA? I
> never manage to follow the lineage of these things.

Not really: while the MMP SoC design is a follow-up to
Intel PXA (using XScale), the later Marvell PXA and MMP
switched over the Sheeva line of CPU cores that
originally came from Marvell Orion/Kirkwood. The earlier
cores were ARMv5 and some even supported Intel's iWMMXt
FPU, the later PJ4 ones were ARMv7 with VFP but were
based on the same microarchitecture.

     Arnd