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

[Honnappa Nagarahalli]

> 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?

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