RE: [PATCH] config/arm: fix Neoverse N2 march flag

[Ruifeng Wang <Ruifeng.Wang@arm.com>]

> -----Original Message-----
> From: pbhagavatula@marvell.com <pbhagavatula@marvell.com>
> Sent: Thursday, June 8, 2023 3:28 PM
> To: jerinj@marvell.com; Ruifeng Wang <Ruifeng.Wang@arm.com>; Bruce Richardson
> <bruce.richardson@intel.com>
> Cc: dev@dpdk.org; Pavan Nikhilesh <pbhagavatula@marvell.com>
> Subject: [PATCH] config/arm: fix Neoverse N2 march flag
> 
> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
> 
> The -march flag of Neoverse N2 should be `armv9-a` when used along with -mcpu=neoverse-n2.
> 
> Fixes: ea85ed1f6882 ("config/arm: increase nodes and cores for Neoverse N2")
> 
> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
> ---
>  config/arm/meson.build | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/config/arm/meson.build b/config/arm/meson.build index 43f6a551a2..d3b4b4917f
> 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -89,7 +89,7 @@ part_number_config_arm = {
>          'march': 'armv8.4-a',
>      },
>      '0xd49': {
> -        'march': 'armv8.5-a',
> +        'march': 'armv9-a',
>          'march_features': ['sve2'],
>          'compiler_options': ['-mcpu=neoverse-n2'],
>          'flags': [
> @@ -630,7 +630,7 @@ if update_flags
>      # probe supported archs and their features
>      candidate_march = ''
>      if part_number_config.has_key('march')
> -        supported_marchs = ['armv8.6-a', 'armv8.5-a', 'armv8.4-a', 'armv8.3-a',
> +        supported_marchs = ['armv9-a', 'armv8.6-a', 'armv8.5-a',

march may fallback to armv8.6-a if compiler doesn't support armv9-a. Is this fallback safe?
I think just remove march from N2 part_number_config is OK. 

> + 'armv8.4-a', 'armv8.3-a',
>                              'armv8.2-a', 'armv8.1-a', 'armv8-a']
>          check_compiler_support = false
>          foreach supported_march: supported_marchs
> --
> 2.25.1