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Message-ID: <2D34CF27-CB0C-4BAE-997C-3DACEB0E66C5@nvidia.com>
Date: Thu, 9 Oct 2025 20:10:28 +0000
From: Edwin Peer <epeer@...dia.com>
To: Alexandre Courbot <acourbot@...dia.com>
CC: Danilo Krummrich <dakr@...nel.org>, Joel Fernandes
<joelagnelf@...dia.com>, Yury Norov <yury.norov@...il.com>, Jesung Yang
<y.j3ms.n@...il.com>, Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor
<alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo
<gary@...yguo.net>, Björn Roy Baron
<bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>, Andreas
Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, Trevor
Gross <tmgross@...ch.edu>, "nouveau@...ts.freedesktop.org"
<nouveau@...ts.freedesktop.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "rust-for-linux@...r.kernel.org"
<rust-for-linux@...r.kernel.org>
Subject: Re: [PATCH RFC v2 1/3] gpu: nova-core: register: use field type for
Into implementation
> On Oct 9, 2025, at 5:37 AM, Alexandre Courbot <acourbot@...dia.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@...dia.com>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.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@...dia.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
>
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