On Wed Oct 29, 2025 at 12:03 PM JST, John Hubbard wrote:
<snip>
> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
> index 206dab2e1335..ed3a2c39edbc 100644
> --- a/drivers/gpu/nova-core/regs.rs
> +++ b/drivers/gpu/nova-core/regs.rs
> @@ -25,6 +25,18 @@
> });
>
> impl NV_PMC_BOOT_0 {
> + pub(crate) fn is_nv04(self) -> bool {
> + // The very first supported GPU was NV04, and it is identified by a
> specific bit pattern in
> + // boot0. This provides a way to check for that, which in turn is
> required in order to avoid
> + // confusing future "next-gen" GPUs with NV04.
> + self.architecture_0() == 0 && (self.0 & 0xff00fff0) == 0x20004000
> + }
> +
> + pub(crate) fn is_next_gen(self) -> bool {
> + // "next-gen" GPUs (some time after Blackwell) will set
> `architecture_0` to 0, and put the
> + // architecture details in boot42 instead.
> + self.architecture_0() == 0 && !self.is_nv04()
> + }
> /// Combines `architecture_0` and `architecture_1` to obtain the
> architecture of the chip.
> pub(crate) fn architecture(self) -> Result<Architecture> {
> Architecture::try_from(
> @@ -43,6 +55,21 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
> }
> }
>
> +register!(NV_PMC_BOOT_42 @ 0x00000108, "Extended architecture information" {
> + 7:0 implementation as u8, "Implementation version of the
> architecture";
> + 15:8 architecture as u8, "Architecture value";
Here you can directly return the `Architecture` type and spare callers
the labor of doing the conversion themselves:
15:8 architecture as u8 ?=> Architecture, "Architecture value";
This allows the implementation of `NV_PMC_BOOT_42` to mirror that of
`NV_PMC_BOOT_0`:
impl NV_PMC_BOOT_42 {
pub(crate) fn chipset(self) -> Result<Chipset> {
self.architecture()
.map(|arch| {
((arch as u32) << Self::IMPLEMENTATION_RANGE.len())
| u32::from(self.implementation())
})
.and_then(Chipset::try_from)
}
}
... but also requires `Architecture` to be `repr(u8)` and to implement
`Default` and `Into<u8>` so it can be used in the `register` macro:
/// Enum representation of the GPU generation.
#[derive(fmt::Debug, Default)]
#[repr(u8)]
pub(crate) enum Architecture {
#[default]
Turing = 0x16,
Ampere = 0x17,
Ada = 0x19,
}
impl From<Architecture> for u8 {
fn from(value: Architecture) -> Self {
// CAST: `Architecture` is `repr(u8)`, so this cast is always
lossless.
value as u8
}
}
These implementations were not needed for `NV_PMC_BOOT_0` because its
`architecture` method is manually implemented as it depends on two
distinct fields.
