Re: [PATCH] ARM: Kconfig: improve ARM_SINGLE_ARMV7M description with Cortex M7

From: Giulio Benetti
Date: Fri Dec 03 2021 - 12:03:39 EST


On 03/12/21 18:01, Vladimir Murzin wrote:
On 12/3/21 4:41 PM, Giulio Benetti wrote:
Hi Vladimir,

On 03/12/21 10:30, Vladimir Murzin wrote:
On 12/2/21 10:20 PM, Giulio Benetti wrote:
ARM_SINGLE_ARMV7M implies Arm Cortex M7 too, so let's add it to
description with M0/M3/M4.

Well it also implies M33 and M55. I'd suggest drop specific implementations
from description - so we do not need to update it each time new compatible
core is released. To account newest cores like M33 and M55 you can rephrase
to:
- ARMv7-M/v8-M

This ^^^ is ok for me. Also, I don't see any M0 used at the moment so no ARMv6-M makes sense, if any in the future we can update. I see M3,M4,M7 for the moment, so ARMv7-M. But at the moment no ARMv8-M, or am I wrong?

We already support PMSAv8 which is ARMv8-M, M33/M55 is in flight [1].

Ah, I've missed that. And great for M33!

Maybe it would be better to add ARMv8-M when there will really be the support, considering also that ARM_SINGLE_ARMV7M is a bit ambiguous to be used with ARMv8-M. So maybe that could be modified too when an ARMv8-M is added.

What do you think about this?

Well, I prefer to touch this as rare as possible, and if we touch
it then ensure we do not need to touch it for a long time ;)

Look at A-class cores,

config ARCH_MULTI_V7
bool "ARMv7 based platforms (Cortex-A, PJ4, Scorpion, Krait)"

it doesn't mention ARMv8, yet it is pretty much possible to run it
on some cores either bare-metal or as a guest (just look under
arch/arm/include/asm/cputype.h)

Ah yeah, thanks for pointing, then I'm going with ARMv7-M/v8-M

These are just config options, not a legal deeds...

+1

Thank you
Best regards
--
Giulio Benetti
Benetti Engineering sas

[1] https://lore.kernel.org/linux-arm-kernel/20211201132908.106711-1-vladimir.murzin@xxxxxxx/T/

Cheers
Vladimir


Best regards