[PATCH v2 3/3] config/arm: allow WFE to be enabled config time

[Pavan Nikhilesh Bhagavatula]

> > On Feb 1, 2024, at 3:57 PM, pbhagavatula at marvell.com wrote:
> >
> > From: Pavan Nikhilesh <pbhagavatula at marvell.com>
> >
> > Allow RTE_ARM_USE_WFE to be enabled at meson configuration
> > time by passing it via c_args instead of modifying
> > `config/arm/meson.build`.
> >
> > Example usage:
> > meson build -Dc_args='-DRTE_ARM_USE_WFE' \
> > --cross-file config/arm/arm64_cn10k_linux_gcc
> >
> > Signed-off-by: Pavan Nikhilesh <pbhagavatula at marvell.com>
> > Acked-by: Chengwen Feng <fengchengwen at huawei.com>
> > Acked-by: Ruifeng Wang <ruifeng.wang at arm.com>
> > ---
> > config/arm/meson.build | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/config/arm/meson.build b/config/arm/meson.build
> > index 6f2308f2fa..3467bef466 100644
> > --- a/config/arm/meson.build
> > +++ b/config/arm/meson.build
> > @@ -17,7 +17,9 @@ flags_common = [
> >         #    ['RTE_ARM64_MEMCPY_ALIGN_MASK', 0xF],
> >         #    ['RTE_ARM64_MEMCPY_STRICT_ALIGN', false],
> >
> > -        ['RTE_ARM_USE_WFE', false],
> > +        # Enable use of ARM wait for event instruction.
> > +        # ['RTE_ARM_USE_WFE', false],
> > +
> So, what is the default value for RTE_ARM_USE_WFE if the user does not pass
> the flag at the command line?
> 

All the checks related to RTE_ARM_USE_WFE see if it is defined or not

#rg "RTE_ARM_USE_WFE"                     
config/arm/meson.build
20:        ['RTE_ARM_USE_WFE', false],
lib/eal/arm/rte_cpuflags.c
166:#ifdef RTE_ARM_USE_WFE
lib/eal/arm/include/rte_pause_64.h
15:#ifdef RTE_ARM_USE_WFE
lib/eal/arm/rte_power_intrinsics.c
20:#ifdef RTE_ARM_USE_WFE
84:#ifdef RTE_ARM_USE_WFE

So default value would be not-defined.

> Can we do it such a way that the flag passed on the command line takes
> precedence?

No, we can't have checks based on flags passed via -Dc_args with the current meson(needs build_options() from 1.1.0).
Only option is to add via meson_option.txt which is not optimal for arch settings.

> 
> >         ['RTE_ARCH_ARM64', true],
> >         ['RTE_CACHE_LINE_SIZE', 128]
> > ]
> > --
> > 2.25.1
> >