Re: [PATCH RFC v2 1/3] gpu: nova-core: register: use field type for Into implementation

[Edwin Peer <epeer@nvidia.com>]

> On Oct 9, 2025, at 5:37 AM, Alexandre Courbot <acourbot@nvidia.com> wrote:
> 
> The getter method of a field works with the field type, but its setter
> expects the type of the register. This leads to an asymmetry in the
> From/Into implementations required for a field with a dedicated type.
> For instance, a field declared as
> 
>    pub struct ControlReg(u32) {
>        3:0 mode as u8 ?=> Mode;
>        ...
>    }
> 
> currently requires the following implementations:
> 
>    impl TryFrom<u8> for Mode {
>      ...
>    }
> 
>    impl From<Mode> for u32 {
>      ...
>    }
> 
> Change this so the `From<Mode>` now needs to be implemented for `u8`,
> i.e. the primitive type of the field. This is more consistent, and will
> become a requirement once we start using the TryFrom/Into derive macros
> to implement these automatically.
> 
> Reported-by: Edwin Peer <epeer@nvidia.com>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
> drivers/gpu/nova-core/falcon.rs      | 38 +++++++++++++++++++++++++-----------
> drivers/gpu/nova-core/regs/macros.rs | 10 +++++-----
> 2 files changed, 32 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/falcon.rs b/drivers/gpu/nova-core/falcon.rs
> index 37e6298195e4..3f505b870601 100644
> --- a/drivers/gpu/nova-core/falcon.rs
> +++ b/drivers/gpu/nova-core/falcon.rs
> @@ -22,11 +22,11 @@
> pub(crate) mod sec2;
> 
> // TODO[FPRI]: Replace with `ToPrimitive`.
> -macro_rules! impl_from_enum_to_u32 {
> +macro_rules! impl_from_enum_to_u8 {
>     ($enum_type:ty) => {
> -        impl From<$enum_type> for u32 {
> +        impl From<$enum_type> for u8 {
>             fn from(value: $enum_type) -> Self {
> -                value as u32
> +                value as u8
>             }
>         }
>     };
> @@ -46,7 +46,7 @@ pub(crate) enum FalconCoreRev {
>     Rev6 = 6,
>     Rev7 = 7,
> }
> -impl_from_enum_to_u32!(FalconCoreRev);
> +impl_from_enum_to_u8!(FalconCoreRev);
> 
> // TODO[FPRI]: replace with `FromPrimitive`.
> impl TryFrom<u8> for FalconCoreRev {
> @@ -81,7 +81,7 @@ pub(crate) enum FalconCoreRevSubversion {
>     Subversion2 = 2,
>     Subversion3 = 3,
> }
> -impl_from_enum_to_u32!(FalconCoreRevSubversion);
> +impl_from_enum_to_u8!(FalconCoreRevSubversion);
> 
> // TODO[FPRI]: replace with `FromPrimitive`.
> impl TryFrom<u8> for FalconCoreRevSubversion {
> @@ -125,7 +125,7 @@ pub(crate) enum FalconSecurityModel {
>     /// Also known as High-Secure, Privilege Level 3 or PL3.
>     Heavy = 3,
> }
> -impl_from_enum_to_u32!(FalconSecurityModel);
> +impl_from_enum_to_u8!(FalconSecurityModel);
> 
> // TODO[FPRI]: replace with `FromPrimitive`.
> impl TryFrom<u8> for FalconSecurityModel {
> @@ -157,7 +157,7 @@ pub(crate) enum FalconModSelAlgo {
>     #[default]
>     Rsa3k = 1,
> }
> -impl_from_enum_to_u32!(FalconModSelAlgo);
> +impl_from_enum_to_u8!(FalconModSelAlgo);
> 
> // TODO[FPRI]: replace with `FromPrimitive`.
> impl TryFrom<u8> for FalconModSelAlgo {
> @@ -179,7 +179,7 @@ pub(crate) enum DmaTrfCmdSize {
>     #[default]
>     Size256B = 0x6,
> }
> -impl_from_enum_to_u32!(DmaTrfCmdSize);
> +impl_from_enum_to_u8!(DmaTrfCmdSize);
> 
> // TODO[FPRI]: replace with `FromPrimitive`.
> impl TryFrom<u8> for DmaTrfCmdSize {
> @@ -202,7 +202,6 @@ pub(crate) enum PeregrineCoreSelect {
>     /// RISC-V core is active.
>     Riscv = 1,
> }
> -impl_from_enum_to_u32!(PeregrineCoreSelect);
> 
> impl From<bool> for PeregrineCoreSelect {
>     fn from(value: bool) -> Self {
> @@ -213,6 +212,15 @@ fn from(value: bool) -> Self {
>     }
> }
> 
> +impl From<PeregrineCoreSelect> for bool {
> +    fn from(value: PeregrineCoreSelect) -> Self {
> +        match value {
> +            PeregrineCoreSelect::Falcon => false,
> +            PeregrineCoreSelect::Riscv => true,
> +        }
> +    }
> +}
> +
> /// Different types of memory present in a falcon core.
> #[derive(Debug, Clone, Copy, PartialEq, Eq)]
> pub(crate) enum FalconMem {
> @@ -236,7 +244,7 @@ pub(crate) enum FalconFbifTarget {
>     /// Non-coherent system memory (System DRAM).
>     NoncoherentSysmem = 2,
> }
> -impl_from_enum_to_u32!(FalconFbifTarget);
> +impl_from_enum_to_u8!(FalconFbifTarget);
> 
> // TODO[FPRI]: replace with `FromPrimitive`.
> impl TryFrom<u8> for FalconFbifTarget {
> @@ -263,7 +271,6 @@ pub(crate) enum FalconFbifMemType {
>     /// Physical memory addresses.
>     Physical = 1,
> }
> -impl_from_enum_to_u32!(FalconFbifMemType);
> 
> /// Conversion from a single-bit register field.
> impl From<bool> for FalconFbifMemType {
> @@ -275,6 +282,15 @@ fn from(value: bool) -> Self {
>     }
> }
> 
> +impl From<FalconFbifMemType> for bool {
> +    fn from(value: FalconFbifMemType) -> Self {
> +        match value {
> +            FalconFbifMemType::Virtual => false,
> +            FalconFbifMemType::Physical => true,
> +        }
> +    }
> +}
> +
> /// Type used to represent the `PFALCON` registers address base for a given falcon engine.
> pub(crate) struct PFalconBase(());
> 
> diff --git a/drivers/gpu/nova-core/regs/macros.rs b/drivers/gpu/nova-core/regs/macros.rs

The examples in the doc comments should also be updated. Otherwise, LGTM.

Reviewed-by: Edwin Peer <epeer@nvidia.com>

Regards,
Edwin Peer

> index 754c14ee7f40..73811a115762 100644
> --- a/drivers/gpu/nova-core/regs/macros.rs
> +++ b/drivers/gpu/nova-core/regs/macros.rs
> @@ -482,7 +482,7 @@ impl $name {
>         register!(
>             @leaf_accessor $name $hi:$lo $field
>             { |f| <$into_type>::from(if f != 0 { true } else { false }) }
> -            $into_type => $into_type $(, $comment)?;
> +            bool $into_type => $into_type $(, $comment)?;
>         );
>     };
> 
> @@ -499,7 +499,7 @@ impl $name {
>             $(, $comment:literal)?;
>     ) => {
>         register!(@leaf_accessor $name $hi:$lo $field
> -            { |f| <$try_into_type>::try_from(f as $type) } $try_into_type =>
> +            { |f| <$try_into_type>::try_from(f as $type) } $type $try_into_type =>
>             ::core::result::Result<
>                 $try_into_type,
>                 <$try_into_type as ::core::convert::TryFrom<$type>>::Error
> @@ -513,7 +513,7 @@ impl $name {
>             $(, $comment:literal)?;
>     ) => {
>         register!(@leaf_accessor $name $hi:$lo $field
> -            { |f| <$into_type>::from(f as $type) } $into_type => $into_type $(, $comment)?;);
> +            { |f| <$into_type>::from(f as $type) } $type $into_type => $into_type $(, $comment)?;);
>     };
> 
>     // Shortcut for non-boolean fields defined without the `=>` or `?=>` syntax.
> @@ -527,7 +527,7 @@ impl $name {
>     // Generates the accessor methods for a single field.
>     (
>         @leaf_accessor $name:ident $hi:tt:$lo:tt $field:ident
> -            { $process:expr } $to_type:ty => $res_type:ty $(, $comment:literal)?;
> +            { $process:expr } $prim_type:tt $to_type:ty => $res_type:ty $(, $comment:literal)?;
>     ) => {
>         ::kernel::macros::paste!(
>         const [<$field:upper _RANGE>]: ::core::ops::RangeInclusive<u8> = $lo..=$hi;
> @@ -559,7 +559,7 @@ pub(crate) fn $field(self) -> $res_type {
>         pub(crate) fn [<set_ $field>](mut self, value: $to_type) -> Self {
>             const MASK: u32 = $name::[<$field:upper _MASK>];
>             const SHIFT: u32 = $name::[<$field:upper _SHIFT>];
> -            let value = (u32::from(value) << SHIFT) & MASK;
> +            let value = (u32::from($prim_type::from(value)) << SHIFT) & MASK;
>             self.0 = (self.0 & !MASK) | value;
> 
>             self
> 
> -- 
> 2.51.0
>