[PATCH v4 06/12] ARM: vfp: Remove workaround for Feroceon CPUs

[Ard Biesheuvel]

On Tue, 21 Mar 2023 at 15:44, Linus Walleij <linus.walleij at linaro.org> wrote:
>
> On Mon, Mar 20, 2023 at 2:19 PM Ard Biesheuvel <ardb at kernel.org> wrote:
>
> > Feroceon CPUs have a non-standard implementation of VFP which reports
> > synchronous VFP exceptions using the async VFP flag. This requires a
> > workaround which is difficult to reconcile with other implementations,
> > making it tricky to support both versions in a single image.
> >
> > Since this is a v5 CPU, it is not supported by armhf and so the
> > likelihood that anybody is using this with recent distros/kernels and
> > rely on the VFP at the same time is extremely low. So let's just disable
> > VFP support on these cores, so we can remove the workaround.
> >
> > This will help future development to support v5 and v6 CPUs with a
> > single kernel image.
> >
> > Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
>
> I agree, I have one of those systems as my NAS, currently running
> an (unsupported) version of ArchLinuxARM:
>
> $ cat /proc/cpuinfo
> processor    : 0
> model name    : Feroceon 88FR131 rev 1 (v5l)
> BogoMIPS    : 83.33
> Features    : swp half thumb fastmult edsp
> CPU implementer    : 0x56
> CPU architecture: 5TE
> CPU variant    : 0x2
> CPU part    : 0x131
> CPU revision    : 1
>
> Hm doesn't even have any VFP, I don't know what spins of this Marvell
> silicon that even does?

Arnd might have some more insight in that. Does this kernel have
CONFIG_VFP enabled?

> Reviewed-by: Linus Walleij <linus.walleij at linaro.org>
>
> I think this is again on the level of a tree falling in the forest and no-one
> being there to hear it, but let's page Nico again because I am pretty
> sure if anyone worked with this it was him.
>
> Yours,
> Linus Walleij