From: Ard Biesheuvel <ardb@kernel.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Nicolas Pitre <nico@fluxnic.net>,
Nicolas Pitre <npitre@baylibre.com>,
linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk,
Frederic Weisbecker <frederic@kernel.org>,
Guenter Roeck <linux@roeck-us.net>,
Peter Zijlstra <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v4 06/12] ARM: vfp: Remove workaround for Feroceon CPUs
Date: Tue, 21 Mar 2023 16:42:50 +0100 [thread overview]
Message-ID: <CAMj1kXFoJfYGpJ80KE0GnUHeLkeYV-N2YC+3VSKO10b5956fMg@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdYKTJxC5nbRqkGC=jnmg=m_oOmWU8mBXmYp2opPjJZj=Q@mail.gmail.com>
On Tue, 21 Mar 2023 at 15:44, Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Mon, Mar 20, 2023 at 2:19 PM Ard Biesheuvel <ardb@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@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@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
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next prev parent reply other threads:[~2023-03-21 15:45 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-20 13:18 [PATCH v4 00/12] ARM: vfp: Switch to C API to en/disable softirqs Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 01/12] ARM: vfp: Pass thread_info pointer to vfp_support_entry Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 02/12] ARM: vfp: Pass successful return address via register R3 Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 03/12] ARM: vfp: Fix broken softirq handling with instrumentation enabled Ard Biesheuvel
2023-04-09 14:29 ` Linux regression tracking (Thorsten Leemhuis)
2023-04-10 20:15 ` Guenter Roeck
2023-03-20 13:18 ` [PATCH v4 04/12] ARM: entry: Fix iWMMXT TIF flag handling Ard Biesheuvel
2023-03-21 14:32 ` Linus Walleij
2023-03-21 19:19 ` Nicolas Pitre
2023-03-21 19:32 ` Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 05/12] ARM: vfp: Record VFP bounces as perf emulation faults Ard Biesheuvel
2023-03-21 14:33 ` Linus Walleij
2023-03-20 13:18 ` [PATCH v4 06/12] ARM: vfp: Remove workaround for Feroceon CPUs Ard Biesheuvel
2023-03-21 14:44 ` Linus Walleij
2023-03-21 15:42 ` Ard Biesheuvel [this message]
2023-03-21 20:40 ` Linus Walleij
2023-03-22 7:26 ` Arnd Bergmann
2023-03-21 20:00 ` Nicolas Pitre
2023-03-20 13:18 ` [PATCH v4 07/12] ARM: vfp: Reimplement VFP exception entry in C code Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 08/12] ARM: kernel: Get rid of thread_info::used_cp[] array Ard Biesheuvel
2023-03-21 14:58 ` Linus Walleij
2023-03-20 13:18 ` [PATCH v4 09/12] ARM: vfp: Use undef hook for handling VFP exceptions Ard Biesheuvel
2023-03-21 14:59 ` Linus Walleij
2023-03-21 15:41 ` Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 10/12] ARM: entry: Disregard Thumb undef exception in coproc dispatch Ard Biesheuvel
2023-03-21 15:05 ` Linus Walleij
2023-03-20 13:18 ` [PATCH v4 11/12] ARM: iwmmxt: Use undef hook to enable coprocessor for task Ard Biesheuvel
2023-03-21 15:06 ` Linus Walleij
2023-03-20 13:18 ` [PATCH v4 12/12] ARM: entry: Make asm coproc dispatch code NWFPE only Ard Biesheuvel
2023-03-21 15:11 ` Linus Walleij
2023-03-23 2:44 ` [PATCH v4 00/12] ARM: vfp: Switch to C API to en/disable softirqs Guenter Roeck
2023-03-23 8:33 ` Ard Biesheuvel
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