[PATCH v8 0/6] gpu: nova: add boot42 support for next-gen GPUs

[PATCH v8 0/6] gpu: nova: add boot42 support for next-gen GPUs

[John Hubbard]

Changes in v8:

1) Added two new patches: convert the remaining ENODEV cases to ENOTSUPP,
   and add dev_err!() report for some (most) cases of unsupported GPUs.

2) Corrected some comments.

3) Added Joel's Reviewed-by, but not yet to the two new patches.

Changes in v7:

1) Added a TODO to eventually remove the Default trait from Architecture.
2) Further refined the logic and comments for reading boot0, then boot42.

Changes in v6:

1) Split out a separate patch for implementing Display for Spec.
2) Moved Spec implementation code to its proper location.
3) Significantly changed the use_boot42_instead() logic, and updated the
   comments accordingly.
4) Fixed the boot42 register and field values, which were wrong (and
   had not been exercised before).
5) Imported Revision, to save a few ::'s.
6) Rebased to the very latest drm-rust-next, which now includes the new
   "one 'use' item per line" updates.

Changes in v5:

Two fixes, both from Timur's review feedback (thanks!):

1) Updated both the cover letter, and patch 3 commit description, with
the correct description of the future contents of NV_PMC_BOOT_0.
2) Removed a trailing "boot42" typo from a comment in the code.

Changes in v4:

1) Simplified and improved the decision logic: reads both arch_0 and
arch_1 fields in boot0, and skips the unnecessary is_nv04() logic as
well. Thanks to Timur Tabi and Danilo for noticing these issues.
2) Added a patch to represent Architecture as a u8. This simplifies a
few things. (Thanks to Alex Courbot. I added your Suggested-by to that
patch.)
3) Enhanced the Revision type to do more, which simplifies the callers.
(Thanks to Danilo.)

Changes in v3:

1) Restored the Revision type as recommended by Danilo, but decoupled it
from boot0.
2) Applied Alex Courbot's suggestion to use TryFrom<NV_PMC_BOOT_0/42>
for Spec.
3) Reflowed the new comment documentation to 100 cols, to avoid wasting
a few vertical lines.

Changes in v2:

1) Restored the Spec type, and used that to encapsulate the subsequent
   boot42 enhancements. Thanks to Danilo Krummrich's feedback for that
   improvement.

v1 cover letter (with typos fixed)

NVIDIA GPUs are moving away from using NV_PMC_BOOT_0 to contain
architecture and revision details, and will instead use NV_PMC_BOOT_42
in the future. NV_PMC_BOOT_0 will contain a specific set of values that
will mean "go read NV_PMC_BOOT_42 instead".

Change the selection logic in Nova so that it will claim Turing and
later GPUs. This will work for the foreseeable future, without any
further code changes here, because all NVIDIA GPUs are considered, from
the oldest supported on Linux (NV04), through the future GPUs.

Add some comment documentation to explain, chronologically, how boot0
and boot42 change with the GPU eras, and how that affects the selection
logic.

Also, remove the Revision type, because Revision is no longer valuable
as a stand-alone type, because we only ever want the full information
that Spec provides.

This is based on today's drm-rust-next, which in turn is based on
Linux 6.18-rc2.


John Hubbard (6):
  gpu: nova-core: implement Display for Spec
  gpu: nova-core: prepare Spec and Revision types for boot0/boot42
  gpu: nova-core: make Architecture behave as a u8 type
  gpu: nova-core: use ENOTSUPP for unsupported GPUs, in all cases
  gpu: nova-core: add boot42 support for next-gen GPUs
  gpu: nova-core: provide a clear error report for unsupported GPUs

 drivers/gpu/nova-core/gpu.rs  | 94 +++++++++++++++++++++++++----------
 drivers/gpu/nova-core/regs.rs | 51 ++++++++++++++++---
 2 files changed, 112 insertions(+), 33 deletions(-)


base-commit: e54ad0cd3673c93cdafda58505eaa81610fe3aef
-- 
2.51.2

[PATCH v8 1/6] gpu: nova-core: implement Display for Spec

[John Hubbard]

Implement Display for Spec. This simplifies the dev_info!() code for
printing banners such as:

    NVIDIA (Chipset: GA104, Architecture: Ampere, Revision: a.1)

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 802e71e4f97d..7fd9e91771a6 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -180,6 +180,18 @@ fn new(bar: &Bar0) -> Result<Spec> {
     }
 }
 
+impl fmt::Display for Spec {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "Chipset: {}, Architecture: {:?}, Revision: {}",
+            self.chipset,
+            self.chipset.arch(),
+            self.revision
+        )
+    }
+}
+
 /// Structure holding the resources required to operate the GPU.
 #[pin_data]
 pub(crate) struct Gpu {
@@ -206,13 +218,7 @@ pub(crate) fn new<'a>(
     ) -> impl PinInit<Self, Error> + 'a {
         try_pin_init!(Self {
             spec: Spec::new(bar).inspect(|spec| {
-                dev_info!(
-                    pdev.as_ref(),
-                    "NVIDIA (Chipset: {}, Architecture: {:?}, Revision: {})\n",
-                    spec.chipset,
-                    spec.chipset.arch(),
-                    spec.revision
-                );
+                dev_info!(pdev.as_ref(),"NVIDIA ({})\n", spec);
             })?,
 
             // We must wait for GFW_BOOT completion before doing any significant setup on the GPU.
-- 
2.51.2

[PATCH v8 2/6] gpu: nova-core: prepare Spec and Revision types for boot0/boot42

[John Hubbard]

1) Decouple Revision from boot0.

2) Enhance Revision, which in turn simplifies Spec::new().

3) Also, slightly enhance the comment about Spec, to be more precise.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs  | 26 ++++++++++++--------------
 drivers/gpu/nova-core/regs.rs | 11 ++++++++++-
 2 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 7fd9e91771a6..8f438188fc03 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -143,17 +143,8 @@ fn try_from(value: u8) -> Result<Self> {
 }
 
 pub(crate) struct Revision {
-    major: u8,
-    minor: u8,
-}
-
-impl Revision {
-    fn from_boot0(boot0: regs::NV_PMC_BOOT_0) -> Self {
-        Self {
-            major: boot0.major_revision(),
-            minor: boot0.minor_revision(),
-        }
-    }
+    pub(crate) major: u8,
+    pub(crate) minor: u8,
 }
 
 impl fmt::Display for Revision {
@@ -162,10 +153,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     }
 }
 
-/// Structure holding the metadata of the GPU.
+/// Structure holding a basic description of the GPU: `Architecture`, `Chipset` and `Revision`.
 pub(crate) struct Spec {
     chipset: Chipset,
-    /// The revision of the chipset.
     revision: Revision,
 }
 
@@ -173,9 +163,17 @@ impl Spec {
     fn new(bar: &Bar0) -> Result<Spec> {
         let boot0 = regs::NV_PMC_BOOT_0::read(bar);
 
+        Spec::try_from(boot0)
+    }
+}
+
+impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
+    type Error = Error;
+
+    fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
         Ok(Self {
             chipset: boot0.chipset()?,
-            revision: Revision::from_boot0(boot0),
+            revision: boot0.revision(),
         })
     }
 }
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 934003cab8a8..8c9af3c59708 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -24,7 +24,8 @@
     },
     gpu::{
         Architecture,
-        Chipset, //
+        Chipset,
+        Revision, //
     },
     num::FromSafeCast,
 };
@@ -56,6 +57,14 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
             })
             .and_then(Chipset::try_from)
     }
+
+    /// Returns the revision information of the chip.
+    pub(crate) fn revision(self) -> Revision {
+        Revision {
+            major: self.major_revision(),
+            minor: self.minor_revision(),
+        }
+    }
 }
 
 // PBUS
-- 
2.51.2

[PATCH v8 3/6] gpu: nova-core: make Architecture behave as a u8 type

[John Hubbard]

This allows Architecture to be passed into register!() and bitfield!()
macro calls. That in turn requires a default implementation for
Architecture.

This simplifies transforming BOOT0 (and later, BOOT42) register values
into GPU architectures.

Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 8f438188fc03..c1eca052968b 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -122,8 +122,14 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 }
 
 /// Enum representation of the GPU generation.
-#[derive(fmt::Debug)]
+///
+/// TODO: remove the `Default` trait implementation, and the `#[default]`
+/// attribute, once the register!() macro (which creates Architecture items) no
+/// longer requires it for read-only fields.
+#[derive(fmt::Debug, Default, Copy, Clone)]
+#[repr(u8)]
 pub(crate) enum Architecture {
+    #[default]
     Turing = 0x16,
     Ampere = 0x17,
     Ada = 0x19,
@@ -142,6 +148,13 @@ fn try_from(value: u8) -> Result<Self> {
     }
 }
 
+impl From<Architecture> for u8 {
+    fn from(value: Architecture) -> Self {
+        // CAST: `Architecture` is `repr(u8)`, so this cast is always lossless.
+        value as u8
+    }
+}
+
 pub(crate) struct Revision {
     pub(crate) major: u8,
     pub(crate) minor: u8,
-- 
2.51.2

[PATCH v8 4/6] gpu: nova-core: use ENOTSUPP for unsupported GPUs, in all cases

[John Hubbard]

Some places in the driver use ENODEV for unsupported GPUs, while others
use ENOTSUPP. ENOTSUPP is more accurate, so change the ENODEV instances
to ENOTSUPP.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Cc: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index c1eca052968b..aa8e881dd474 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -62,7 +62,7 @@ impl TryFrom<u32> for Chipset {
             fn try_from(value: u32) -> Result<Self, Self::Error> {
                 match value {
                     $( $value => Ok(Chipset::$variant), )*
-                    _ => Err(ENODEV),
+                    _ => Err(ENOTSUPP),
                 }
             }
         }
@@ -143,7 +143,7 @@ fn try_from(value: u8) -> Result<Self> {
             0x16 => Ok(Self::Turing),
             0x17 => Ok(Self::Ampere),
             0x19 => Ok(Self::Ada),
-            _ => Err(ENODEV),
+            _ => Err(ENOTSUPP),
         }
     }
 }
-- 
2.51.2

[PATCH v8 5/6] gpu: nova-core: add boot42 support for next-gen GPUs

[John Hubbard]

NVIDIA GPUs are moving away from using NV_PMC_BOOT_0 to contain
architecture and revision details, and will instead use NV_PMC_BOOT_42
in the future. NV_PMC_BOOT_0 will contain a specific set of values
that will mean "go read NV_PMC_BOOT_42 instead".

Change the selection logic in Nova so that it will claim Turing and
later GPUs. This will work for the foreseeable future, without any
further code changes here, because all NVIDIA GPUs are considered, from
the oldest supported on Linux (NV04), through the future GPUs.

Add some comment documentation to explain, chronologically, how boot0
and boot42 change with the GPU eras, and how that affects the selection
logic.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs  | 32 +++++++++++++++++++++++++++-----
 drivers/gpu/nova-core/regs.rs | 22 ++++++++++++++++------
 2 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index aa8e881dd474..9bc94811741c 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -174,19 +174,41 @@ pub(crate) struct Spec {
 
 impl Spec {
     fn new(bar: &Bar0) -> Result<Spec> {
+        // Some brief notes about boot0 and boot42, in chronological order:
+        //
+        // NV04 through NV50:
+        //
+        //    Not supported by Nova. boot0 is necessary and sufficient to identify these GPUs.
+        //    boot42 may not even exist on some of these GPUs.
+        //
+        // Fermi through Volta:
+        //
+        //     Not supported by Nova. boot0 is still sufficient to identify these GPUs, but boot42
+        //     is also guaranteed to be both present and accurate.
+        //
+        // Turing and later:
+        //
+        //     Supported by Nova. Identified by first checking boot0 to ensure that the GPU is not
+        //     from an earlier (pre-Fermi) era, and then using boot42 to precisely identify the GPU.
+        //     Somewhere in the Rubin timeframe, boot0 will no longer have space to add new GPU IDs.
+
         let boot0 = regs::NV_PMC_BOOT_0::read(bar);
 
-        Spec::try_from(boot0)
+        if boot0.is_older_than_fermi() {
+            return Err(ENOTSUPP);
+        }
+
+        Spec::try_from(regs::NV_PMC_BOOT_42::read(bar))
     }
 }
 
-impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
+impl TryFrom<regs::NV_PMC_BOOT_42> for Spec {
     type Error = Error;
 
-    fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
+    fn try_from(boot42: regs::NV_PMC_BOOT_42) -> Result<Self> {
         Ok(Self {
-            chipset: boot0.chipset()?,
-            revision: boot0.revision(),
+            chipset: boot42.chipset()?,
+            revision: boot42.revision(),
         })
     }
 }
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 8c9af3c59708..81097e83c276 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -41,14 +41,24 @@
 });
 
 impl NV_PMC_BOOT_0 {
-    /// Combines `architecture_0` and `architecture_1` to obtain the architecture of the chip.
-    pub(crate) fn architecture(self) -> Result<Architecture> {
-        Architecture::try_from(
-            self.architecture_0() | (self.architecture_1() << Self::ARCHITECTURE_0_RANGE.len()),
-        )
+    pub(crate) fn is_older_than_fermi(self) -> bool {
+        // From https://github.com/NVIDIA/open-gpu-doc/tree/master/manuals :
+        const NV_PMC_BOOT_0_ARCHITECTURE_GF100: u8 = 0xc;
+
+        // Older chips left arch1 zeroed out. That, combined with an arch0 value that is less than
+        // GF100, means "older than Fermi".
+        self.architecture_1() == 0 && self.architecture_0() < NV_PMC_BOOT_0_ARCHITECTURE_GF100
     }
+}
+
+register!(NV_PMC_BOOT_42 @ 0x00000a00, "Extended architecture information" {
+    15:12   minor_revision as u8, "Minor revision of the chip";
+    19:16   major_revision as u8, "Major revision of the chip";
+    23:20   implementation as u8, "Implementation version of the architecture";
+    29:24   architecture as u8 ?=> Architecture, "Architecture value";
+});
 
-    /// Combines `architecture` and `implementation` to obtain a code unique to the chipset.
+impl NV_PMC_BOOT_42 {
     pub(crate) fn chipset(self) -> Result<Chipset> {
         self.architecture()
             .map(|arch| {
-- 
2.51.2

[PATCH v8 6/6] gpu: nova-core: provide a clear error report for unsupported GPUs

[John Hubbard]

Pass in a PCI device to Spec::new(), and provide a Display
implementation for boot42, in order to provide a clear, concise report
of what happened: the driver read NV_PMC_BOOT42, and found that the GPU
is not supported.

For very old GPUs (older than Fermi), the driver still returns ENOTSUPP,
but it does so without a driver-specific dmesg report. That is exactly
appropriate, because if such a GPU is installed, it can only be
supported by Nouveau. And if so, the user is not helped by additional
error messages from Nova.

Here's the full dmesg output for a Blackwell (not yet supported) GPU:

NovaCore 0000:01:00.0: Probe Nova Core GPU driver.
NovaCore 0000:01:00.0: Unsupported chipset: boot42 = 0x1b2a1000 (architecture 0x1b, implementation 0x2)
NovaCore 0000:01:00.0: probe with driver NovaCore failed with error -524

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Cc: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs  |  9 ++++++---
 drivers/gpu/nova-core/regs.rs | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 9bc94811741c..7f8a5c1ed9f1 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -173,7 +173,7 @@ pub(crate) struct Spec {
 }
 
 impl Spec {
-    fn new(bar: &Bar0) -> Result<Spec> {
+    fn new(dev: &device::Device, bar: &Bar0) -> Result<Spec> {
         // Some brief notes about boot0 and boot42, in chronological order:
         //
         // NV04 through NV50:
@@ -198,7 +198,10 @@ fn new(bar: &Bar0) -> Result<Spec> {
             return Err(ENOTSUPP);
         }
 
-        Spec::try_from(regs::NV_PMC_BOOT_42::read(bar))
+        let boot42 = regs::NV_PMC_BOOT_42::read(bar);
+        Spec::try_from(boot42).inspect_err(|_| {
+            dev_err!(dev, "Unsupported chipset: {}\n", boot42);
+        })
     }
 }
 
@@ -250,7 +253,7 @@ pub(crate) fn new<'a>(
         bar: &'a Bar0,
     ) -> impl PinInit<Self, Error> + 'a {
         try_pin_init!(Self {
-            spec: Spec::new(bar).inspect(|spec| {
+            spec: Spec::new(pdev.as_ref(), bar).inspect(|spec| {
                 dev_info!(pdev.as_ref(),"NVIDIA ({})\n", spec);
             })?,
 
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 81097e83c276..d6da8bc2e242 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -68,6 +68,12 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
             .and_then(Chipset::try_from)
     }
 
+    /// Returns the raw architecture value from the register.
+    fn architecture_raw(self) -> u8 {
+        ((self.0 >> Self::ARCHITECTURE_RANGE.start()) & ((1 << Self::ARCHITECTURE_RANGE.len()) - 1))
+            as u8
+    }
+
     /// Returns the revision information of the chip.
     pub(crate) fn revision(self) -> Revision {
         Revision {
@@ -77,6 +83,18 @@ pub(crate) fn revision(self) -> Revision {
     }
 }
 
+impl kernel::fmt::Display for NV_PMC_BOOT_42 {
+    fn fmt(&self, f: &mut kernel::fmt::Formatter<'_>) -> kernel::fmt::Result {
+        write!(
+            f,
+            "boot42 = 0x{:08x} (architecture 0x{:x}, implementation 0x{:x})",
+            self.0,
+            self.architecture_raw(),
+            self.implementation()
+        )
+    }
+}
+
 // PBUS
 
 register!(NV_PBUS_SW_SCRATCH @ 0x00001400[64]  {});
-- 
2.51.2

Re: [PATCH v8 5/6] gpu: nova-core: add boot42 support for next-gen GPUs

[Alexandre Courbot]

On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
<snip>
> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
> index 8c9af3c59708..81097e83c276 100644
> --- a/drivers/gpu/nova-core/regs.rs
> +++ b/drivers/gpu/nova-core/regs.rs
> @@ -41,14 +41,24 @@
>  });
>  
>  impl NV_PMC_BOOT_0 {
> -    /// Combines `architecture_0` and `architecture_1` to obtain the architecture of the chip.
> -    pub(crate) fn architecture(self) -> Result<Architecture> {
> -        Architecture::try_from(
> -            self.architecture_0() | (self.architecture_1() << Self::ARCHITECTURE_0_RANGE.len()),
> -        )
> +    pub(crate) fn is_older_than_fermi(self) -> bool {
> +        // From https://github.com/NVIDIA/open-gpu-doc/tree/master/manuals :
> +        const NV_PMC_BOOT_0_ARCHITECTURE_GF100: u8 = 0xc;
> +
> +        // Older chips left arch1 zeroed out. That, combined with an arch0 value that is less than
> +        // GF100, means "older than Fermi".
> +        self.architecture_1() == 0 && self.architecture_0() < NV_PMC_BOOT_0_ARCHITECTURE_GF100
>      }
> +}
> +
> +register!(NV_PMC_BOOT_42 @ 0x00000a00, "Extended architecture information" {
> +    15:12   minor_revision as u8, "Minor revision of the chip";
> +    19:16   major_revision as u8, "Major revision of the chip";
> +    23:20   implementation as u8, "Implementation version of the architecture";
> +    29:24   architecture as u8 ?=> Architecture, "Architecture value";
> +});
>  
> -    /// Combines `architecture` and `implementation` to obtain a code unique to the chipset.

This comment for the `chipset` method got deleted. Is there a reason? If not I'll restore it when applying.

Re: [PATCH v8 2/6] gpu: nova-core: prepare Spec and Revision types for boot0/boot42

[Alexandre Courbot]

On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
> 1) Decouple Revision from boot0.
>
> 2) Enhance Revision, which in turn simplifies Spec::new().
>
> 3) Also, slightly enhance the comment about Spec, to be more precise.
>
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Timur Tabi <ttabi@nvidia.com>
> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>  drivers/gpu/nova-core/gpu.rs  | 26 ++++++++++++--------------
>  drivers/gpu/nova-core/regs.rs | 11 ++++++++++-
>  2 files changed, 22 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index 7fd9e91771a6..8f438188fc03 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -143,17 +143,8 @@ fn try_from(value: u8) -> Result<Self> {
>  }
>  
>  pub(crate) struct Revision {
> -    major: u8,
> -    minor: u8,
> -}
> -
> -impl Revision {
> -    fn from_boot0(boot0: regs::NV_PMC_BOOT_0) -> Self {
> -        Self {
> -            major: boot0.major_revision(),
> -            minor: boot0.minor_revision(),
> -        }
> -    }
> +    pub(crate) major: u8,
> +    pub(crate) minor: u8,

Something felt a bit off with this diff, and I only realized why now.

We are moving, for no good reason, the creation of `Revision` into the
boot0 (and later boot42) register, which forces us to increase the
visibility of its fields.

And while `Revision` is now created by a method of the register it
originates from, `Spec` for some reason isn't, and we even add a
`TryFrom` implementation for it here. This creates an asymmetry that has
no justification afaict.

Instead, what if we replaced this `from_boot0` method by a `From<BOOT0>`
implementation? That way, we have consistency in how we derive our chip
information structures, and this patch can be reduced to this (with the
other changes below):

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index dfeba9d5d8f6..57c20d1e7274 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -147,8 +147,8 @@ pub(crate) struct Revision {
     minor: u8,
 }

-impl Revision {
-    fn from_boot0(boot0: regs::NV_PMC_BOOT_0) -> Self {
+impl From<regs::NV_PMC_BOOT_0> for Revision {
+    fn from(boot0: regs::NV_PMC_BOOT_0) -> Self {
         Self {
             major: boot0.major_revision(),
             minor: boot0.minor_revision(),
@@ -162,10 +162,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     }
 }

-/// Structure holding the metadata of the GPU.
+/// Structure holding a basic description of the GPU: `Chipset` and `Revision`.
 pub(crate) struct Spec {
     chipset: Chipset,
-    /// The revision of the chipset.
     revision: Revision,
 }

@@ -173,9 +172,17 @@ impl Spec {
     fn new(bar: &Bar0) -> Result<Spec> {
         let boot0 = regs::NV_PMC_BOOT_0::read(bar);

+        Spec::try_from(boot0)
+    }
+}
+
+impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
+    type Error = Error;
+
+    fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
         Ok(Self {
             chipset: boot0.chipset()?,
-            revision: Revision::from_boot0(boot0),
+            revision: boot0.into(),
         })
     }
 }

... and the subsequent patches also get some simplification.

>  }
>  
>  impl fmt::Display for Revision {
> @@ -162,10 +153,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
>      }
>  }
>  
> -/// Structure holding the metadata of the GPU.
> +/// Structure holding a basic description of the GPU: `Architecture`, `Chipset` and `Revision`.

There is no `Architecture` in this structure though?

>  pub(crate) struct Spec {
>      chipset: Chipset,
> -    /// The revision of the chipset.
>      revision: Revision,
>  }
>  
> @@ -173,9 +163,17 @@ impl Spec {
>      fn new(bar: &Bar0) -> Result<Spec> {
>          let boot0 = regs::NV_PMC_BOOT_0::read(bar);
>  
> +        Spec::try_from(boot0)
> +    }
> +}
> +
> +impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
> +    type Error = Error;
> +
> +    fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
>          Ok(Self {
>              chipset: boot0.chipset()?,
> -            revision: Revision::from_boot0(boot0),
> +            revision: boot0.revision(),
>      }
>          })
>  }
> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
> index 934003cab8a8..8c9af3c59708 100644
> --- a/drivers/gpu/nova-core/regs.rs
> +++ b/drivers/gpu/nova-core/regs.rs
> @@ -24,7 +24,8 @@
>      },
>      gpu::{
>          Architecture,
> -        Chipset, //
> +        Chipset,
> +        Revision, //
>      },
>      num::FromSafeCast,
>  };
> @@ -56,6 +57,14 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
>              })
>              .and_then(Chipset::try_from)
>      }
> +
> +    /// Returns the revision information of the chip.
> +    pub(crate) fn revision(self) -> Revision {
> +        Revision {
> +            major: self.major_revision(),
> +            minor: self.minor_revision(),
> +        }
> +    }

With the `From<BOOT0> for Revision` implementation we can also drop this
method.

Re: [PATCH v8 4/6] gpu: nova-core: use ENOTSUPP for unsupported GPUs, in all cases

[Alexandre Courbot]

On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
> Some places in the driver use ENODEV for unsupported GPUs, while others
> use ENOTSUPP. ENOTSUPP is more accurate, so change the ENODEV instances
> to ENOTSUPP.

Mmm actually I suspect we do want to return `ENODEV` in those cases, for
the driver core to interpret the error as "I reject this particular
device":

https://elixir.bootlin.com/linux/v6.13/source/drivers/base/dd.c#L588

Re: [PATCH v8 1/6] gpu: nova-core: implement Display for Spec

[Alexandre Courbot]

On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
> Implement Display for Spec. This simplifies the dev_info!() code for
> printing banners such as:
>
>     NVIDIA (Chipset: GA104, Architecture: Ampere, Revision: a.1)
>
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Timur Tabi <ttabi@nvidia.com>
> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

Pushed this one to drm-rust-next, thanks!

Re: [PATCH v8 4/6] gpu: nova-core: use ENOTSUPP for unsupported GPUs, in all cases

[John Hubbard]

On 11/14/25 7:03 AM, Alexandre Courbot wrote:
> On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
>> Some places in the driver use ENODEV for unsupported GPUs, while others
>> use ENOTSUPP. ENOTSUPP is more accurate, so change the ENODEV instances
>> to ENOTSUPP.
> 
> Mmm actually I suspect we do want to return `ENODEV` in those cases, for
> the driver core to interpret the error as "I reject this particular
> device":
> 
> https://elixir.bootlin.com/linux/v6.13/source/drivers/base/dd.c#L588
> 

OK, so I guess I'll drop this patch and use ENODEV for this situation,
for now at least.

Later, separately, I might just go on a tiny crusade to improve the
driver base, such as:

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 13ab98e033ea..100fd8886b8d 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -588,6 +588,7 @@ static int call_driver_probe(struct device *dev, const struct device_driver *drv
                dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
                break;
        case -ENODEV:
+       case -ENOTSUPP:
        case -ENXIO:
                dev_dbg(dev, "probe with driver %s rejects match %d\n",
                        drv->name, ret);


thanks,
-- 
John Hubbard

Re: [PATCH v8 5/6] gpu: nova-core: add boot42 support for next-gen GPUs

[John Hubbard]

On 11/14/25 6:01 AM, Alexandre Courbot wrote:
> On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
> <snip>
>> +register!(NV_PMC_BOOT_42 @ 0x00000a00, "Extended architecture information" {
>> +    15:12   minor_revision as u8, "Minor revision of the chip";
>> +    19:16   major_revision as u8, "Major revision of the chip";
>> +    23:20   implementation as u8, "Implementation version of the architecture";
>> +    29:24   architecture as u8 ?=> Architecture, "Architecture value";
>> +});
>>  
>> -    /// Combines `architecture` and `implementation` to obtain a code unique to the chipset.
> 
> This comment for the `chipset` method got deleted. Is there a reason? If not I'll restore it when applying.

Ah yes. It got deleted because NV_PMC_BOOT_0::chipset() also got deleted.
And then, I didn't add a corresponding comment for NV_PMC_BOOT_42::chipset().

I'll add it. I have to respin anyway. Thanks for catching it!


thanks,
-- 
John Hubbard

Re: [PATCH v8 2/6] gpu: nova-core: prepare Spec and Revision types for boot0/boot42

[John Hubbard]

On 11/14/25 6:37 AM, Alexandre Courbot wrote:
> On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
...
> Something felt a bit off with this diff, and I only realized why now.
> 
> We are moving, for no good reason, the creation of `Revision` into the
> boot0 (and later boot42) register, which forces us to increase the
> visibility of its fields.
> 
> And while `Revision` is now created by a method of the register it
> originates from, `Spec` for some reason isn't, and we even add a
> `TryFrom` implementation for it here. This creates an asymmetry that has
> no justification afaict.
> 
> Instead, what if we replaced this `from_boot0` method by a `From<BOOT0>`
> implementation? That way, we have consistency in how we derive our chip
> information structures, and this patch can be reduced to this (with the
> other changes below):

Yes, that allows leaving Revision's members private, which shows that
we're laying out the objects in a better way.

I've implemented this for v9.

> 
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index dfeba9d5d8f6..57c20d1e7274 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -147,8 +147,8 @@ pub(crate) struct Revision {
>      minor: u8,
>  }
> 
> -impl Revision {
> -    fn from_boot0(boot0: regs::NV_PMC_BOOT_0) -> Self {
> +impl From<regs::NV_PMC_BOOT_0> for Revision {
> +    fn from(boot0: regs::NV_PMC_BOOT_0) -> Self {
>          Self {
>              major: boot0.major_revision(),
>              minor: boot0.minor_revision(),
> @@ -162,10 +162,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
>      }
>  }
> 
> -/// Structure holding the metadata of the GPU.
> +/// Structure holding a basic description of the GPU: `Chipset` and `Revision`.
>  pub(crate) struct Spec {
>      chipset: Chipset,
> -    /// The revision of the chipset.
>      revision: Revision,
>  }
> 
> @@ -173,9 +172,17 @@ impl Spec {
>      fn new(bar: &Bar0) -> Result<Spec> {
>          let boot0 = regs::NV_PMC_BOOT_0::read(bar);
> 
> +        Spec::try_from(boot0)
> +    }
> +}
> +
> +impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
> +    type Error = Error;
> +
> +    fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
>          Ok(Self {
>              chipset: boot0.chipset()?,
> -            revision: Revision::from_boot0(boot0),
> +            revision: boot0.into(),
>          })
>      }
>  }
> 
> ... and the subsequent patches also get some simplification.
> 
>>  }
>>  
>>  impl fmt::Display for Revision {
>> @@ -162,10 +153,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
>>      }
>>  }
>>  
>> -/// Structure holding the metadata of the GPU.
>> +/// Structure holding a basic description of the GPU: `Architecture`, `Chipset` and `Revision`.
> 
> There is no `Architecture` in this structure though?
> 
>>  pub(crate) struct Spec {
>>      chipset: Chipset,
>> -    /// The revision of the chipset.
>>      revision: Revision,
>>  }
>>  
>> @@ -173,9 +163,17 @@ impl Spec {
>>      fn new(bar: &Bar0) -> Result<Spec> {
>>          let boot0 = regs::NV_PMC_BOOT_0::read(bar);
>>  
>> +        Spec::try_from(boot0)
>> +    }
>> +}
>> +
>> +impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
>> +    type Error = Error;
>> +
>> +    fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
>>          Ok(Self {
>>              chipset: boot0.chipset()?,
>> -            revision: Revision::from_boot0(boot0),
>> +            revision: boot0.revision(),
>>      }
>>          })
>>  }
>> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
>> index 934003cab8a8..8c9af3c59708 100644
>> --- a/drivers/gpu/nova-core/regs.rs
>> +++ b/drivers/gpu/nova-core/regs.rs
>> @@ -24,7 +24,8 @@
>>      },
>>      gpu::{
>>          Architecture,
>> -        Chipset, //
>> +        Chipset,
>> +        Revision, //
>>      },
>>      num::FromSafeCast,
>>  };
>> @@ -56,6 +57,14 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
>>              })
>>              .and_then(Chipset::try_from)
>>      }
>> +
>> +    /// Returns the revision information of the chip.
>> +    pub(crate) fn revision(self) -> Revision {
>> +        Revision {
>> +            major: self.major_revision(),
>> +            minor: self.minor_revision(),
>> +        }
>> +    }
> 
> With the `From<BOOT0> for Revision` implementation we can also drop this
> method.

Yes. Done.


thanks,
-- 
John Hubbard