Creating armv7 MACHINE_ARCH

[Mark Millard]

On 2017-Jun-12, at 8:39 AM, Warner Losh <imp at bsdimp.com> wrote:

> . . .
> 
> Plus, we aren't quite doing what Ian wanted. He wanted a full rename. The
> proposal on the able is to add an armv7 TARGET_ARCH in 12. Not to rename or
> remove armv6. Sadly, that will still be there since the RPI foundation
> keeps finding new ways to repackage the rpi into new boards that are just
> too cheap to ignore.

On 2017-Jun-12, at 6:59 AM, Andrew Turner <andrew at fubar.geek.nz> wrote:

> I like this. My understanding is adding armv7 would also fix many of the currently broken ports that assume they are being built for armv7 as many Linux distros target ARMv7+.
> 
> It should also be noted the GENERIC kernel is likely to only ever target ARMv7+ even without an armv7 TARGET_ARCH.


Hopefully the choices related to TARGET and TARGET_ARCH
for armv7 end up identifying the context to port builds
so that many would just automatically do the right thing.


As for GENERIC:

powerpc has. . .

TARGET=powerpc TARGET_ARCH=powerpc   and GENERIC
TARGET=powerpc TARGET_ARCH=powerpc64 and GENERIC64

So there is precedent for more than one GENERIC*
for a family, with which one being appropriate
being based on TARGET_ARCH.

For powerpc TARGET=powerpc implicitly uses
TARGET_ARCH=powerpc when TARGET_ARCH is not
specified (if I remember right). Which should
be the default for armv6 vs. armv7 might go
the other direction (TARGET_ARCH=armv7 by
default).


Side note:

A caution about talking about "rpi2" as
an example. . .

Raspberry Pi 2 Model B V1.2 is Cortex-A53 based
(so arm64/aarch64). (A BCM2837, not a BCM2836.)
This dates about to something like 2014 based
on the pictures showing the (c) notice on the
boards.

V1.1 and before were armv7 (BCM2836) based.

Unless a kernel and world are made that can
also configure/handle a Cortex-A53 in a
armv7-like manor there will be two different
GENERIC builds in order to span the "rpi2"
family, based on just V1.2+ vs. V1.1 and
before.

(A single, modern distribution of the official
Raspbian software for the rpi2 does support
all the V1.x boards if I understand right.)

===
Mark Millard
markmi at dsl-only.net