[yocto] cortexa9t2hf instead of cortexa9hf

[Zoran Stojsavljevic]

Hello Arno,

Let me try to explain my point of view. Since here (my best guess) we
have some asynchronous bitbake code which went South upon introducing
T2 HW extension.

Point [1]: as far as I understand arm, cortexa9t2hf is is just a
superset of previous cortexa9hf (HW wise). NEON HW extension (NEON
media coprocessor) exists in both of them. In other words:
cortexa9t2hf = cortexa9hf HW + T2 HW extension.

Point [2]:
> bitbake gives me in 2.5:
> TUNE_FEATURES        = "arm armv7a vfp thumb neon callconvention-hard cortexa9"
> TARGET_FPU           = "hard"
>
> and in 2.7:
> TUNE_FEATURES        = "arm vfp cortexa9 neon thumb callconvention-hard"
> TARGET_FPU           = "hard"

These two lines are the same: you are able to use 32b arm mode, 16bit
thumb mode, using armv7 HW with neon HW extension, and using HW FP
extension as well. The Cortex in both cases is A9.

I expect that somebody somewhere in bitbake version 1.42 - 100% sure
(since 2.5/Sumo uses bitbake 1.38) dropped "armv7a" as TUNE FEATURE,
and I have no idea if this is done intentionally or not.

Because of that I copied Alex and Ross to CC: into email, so they
should unveil this mystery (I would prefer "armv7" to stay in bitbake
1.42, since A8 and A9 belongs to armv7, A15 belongs to armv8 (IIRC).

Bottom line: nothing to be done by you, Arno, seems that bitbake 1.42
should return "armv7" as TUNE FEATURE.

Best Regards,
Zoran
_______


On Mon, Jun 17, 2019 at 3:00 PM Arno Steffens <star at gmx.li> wrote:
>
> Hello Zoran,
> thanks. As far as I understand is thumb2 another mode of coding, that might create more compact code.
> But I want to keep all compatible to my previous tool-chain and settings.
> The only file where I can found this "cortexa9t2hf" is
> ./meta/conf/machine/include/tune-cortexa9.inc
> but I can't see how I can control Yocto to generate "cortexa9hf-neon" as before.
> Or have I been wrong the time before?
>
> bitbake gives me in 2.5:
>
> TUNE_FEATURES        = "arm armv7a vfp thumb neon callconvention-hard cortexa9"
> TARGET_FPU           = "hard"
>
> and in 2.7:
> TUNE_FEATURES        = "arm vfp cortexa9 neon thumb callconvention-hard"
> TARGET_FPU           = "hard"
>
> so armv7a seem to be missing. In terms of thumb both is same. But is that the reason? Where to set it?
> Arno
>
> >
> > Hello Arno,
> >
> > Your question, per say, has little to do with YOCTO forum. But I'll
> > try (as my best) to answer your question.
> >
> > Cortexa9hf should be armv7 A9 Hard Floating (it contains HW FP unit).
> >
> > Cortexa9t2hf is by analogy armv7 A9 T2 Hard Floating. Now, the
> > question is what is T2? T2 is addition to the previous architecture
> > Cortexa9hf, and addition is Thumb-2 mode.
> >
> > Hope this helps,
> >
> > Zoran
> > _______
> >
> > On Mon, Jun 17, 2019 at 2:03 PM Arno Steffens <star at gmx.li> wrote:
> > >
> > > I switched from Yocto 2.5 to 2.7 and recognised a new architetcure name.
> > > Instead of cortexa9hf it is now build for cortexa9t2hf? Did I do something wrong or what exactly does this t2 mean?
> > > Target system is a Zynq7020 system.
> > > --
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> >