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

[Pavan Nikhilesh Bhagavatula]

> -----Original Message-----
> From: Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com>
> Sent: Saturday, February 10, 2024 10:07 PM
> To: Pavan Nikhilesh Bhagavatula <pbhagavatula at marvell.com>
> Cc: Jerin Jacob <jerinj at marvell.com>; juraj.linkes at pantheon.tech; nd
> <nd at arm.com>; Ruifeng Wang <Ruifeng.Wang at arm.com>; Bruce Richardson
> <bruce.richardson at intel.com>; dev at dpdk.org; Chengwen Feng
> <fengchengwen at huawei.com>; Wathsala Wathawana Vithanage
> <wathsala.vithanage at arm.com>; Dhruv Tripathi <Dhruv.Tripathi at arm.com>
> Subject: [EXT] Re: [PATCH v2 3/3] config/arm: allow WFE to be enabled config
> time
> 
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> ----------------------------------------------------------------------
> 
> 
> > On Feb 10, 2024, at 12:47 AM, Pavan Nikhilesh Bhagavatula
> <pbhagavatula at marvell.com> wrote:
> >
> >>> 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.
> 
> Ack
> Do you expect the users to enable this flag by default for cn10k?
> 

No, AFAIK only certain users are going to enable it, mostly L1.

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