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

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

> -----Original Message-----
> From: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>
> Sent: Thursday, June 8, 2023 8:59 PM
> To: Ruifeng Wang <Ruifeng.Wang@arm.com>; jerinj@marvell.com; Bruce Richardson
> <bruce.richardson@intel.com>
> Cc: dev@dpdk.org; Juraj Linkeš <juraj.linkes@pantheon.tech>; nd <nd@arm.com>
> Subject: RE: [PATCH] config/arm: fix Neoverse N2 march flag
> 
> 
> 
> > -----Original Message-----
> > From: Ruifeng Wang <Ruifeng.Wang@arm.com>
> > Sent: Thursday, June 8, 2023 4:12 PM
> > To: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>; Jerin
> > Jacob Kollanukkaran <jerinj@marvell.com>; Bruce Richardson
> > <bruce.richardson@intel.com>
> > Cc: dev@dpdk.org; Juraj Linkeš <juraj.linkes@pantheon.tech>; nd
> > <nd@arm.com>
> > Subject: [EXT] RE: [PATCH] config/arm: fix Neoverse N2 march flag
> >
> > External Email
> >
> > ----------------------------------------------------------------------
> > > -----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?
> 
> Yeah, looks like we need to have a fallback arch if compiler doesn't support a given march
> Armv8.5-a in this case.
> 
> > I think just remove march from N2 part_number_config is OK.
> 
> I will remove the march from part number config for now.
> But we should work on defining a fallback arch in future as there will always be a
> compiler support mismatch.

Agree. Need to adapt this for v9-a.

> 
> >
> > > + '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