linux-kernel - [PATCH v2 07/21] gpu: nova-core: fix layout of NV_PMC_BOOT

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Message-Id: <20250501-nova-frts-v2-7-b4a137175337@nvidia.com>
Date: Thu, 01 May 2025 21:58:25 +0900
From: Alexandre Courbot <acourbot@...dia.com>
To: 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 <benno.lossin@...ton.me>, 
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 Jonathan Corbet <corbet@....net>
Cc: John Hubbard <jhubbard@...dia.com>, Ben Skeggs <bskeggs@...dia.com>, 
 Joel Fernandes <joelagnelf@...dia.com>, Timur Tabi <ttabi@...dia.com>, 
 Alistair Popple <apopple@...dia.com>, linux-kernel@...r.kernel.org, 
 rust-for-linux@...r.kernel.org, nouveau@...ts.freedesktop.org, 
 dri-devel@...ts.freedesktop.org, Alexandre Courbot <acourbot@...dia.com>
Subject: [PATCH v2 07/21] gpu: nova-core: fix layout of NV_PMC_BOOT_0

The layout of NV_PMC_BOOT_0 has two small issues:

- The "chipset" field, while useful to identify a chip, is actually an
  aggregate of two distinct fields named "architecture" and
  "implementation".
- The "architecture" field is split, with its MSB being at a different
  location than the rest of its bits.

Redefine the register layout to match its actual definition as provided
by OpenRM and expose the fully-constructed "architecture" field through
our own "Architecture" type. The "chipset" pseudo-field is also useful
to have, so keep providing it.

Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
---
 drivers/gpu/nova-core/gpu.rs  | 19 ++++++++++++++++---
 drivers/gpu/nova-core/regs.rs | 26 ++++++++++++++++++++++++--
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index f95f095baa68c9f7ffe3b1e615548aac5c2a0c6c..64c38425098c19360a7c938f2b86a55ca3c48880 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -101,9 +101,22 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 /// Enum representation of the GPU generation.
 #[derive(fmt::Debug)]
 pub(crate) enum Architecture {
-    Turing,
-    Ampere,
-    Ada,
+    Turing = 0x16,
+    Ampere = 0x17,
+    Ada = 0x19,
+}
+
+impl TryFrom<u8> for Architecture {
+    type Error = Error;
+
+    fn try_from(value: u8) -> core::result::Result<Self, Self::Error> {
+        match value {
+            0x16 => Ok(Self::Turing),
+            0x17 => Ok(Self::Ampere),
+            0x19 => Ok(Self::Ada),
+            _ => Err(ENODEV),
+        }
+    }
 }
 
 pub(crate) struct Revision {
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 498fefb52f33bf01518f19d32287962f1fdc3224..bfb9555b203ff880c0fc373bb22e5ce6048015d4 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -4,15 +4,37 @@
 // but are mapped to types.
 #![allow(non_camel_case_types)]
 
+use kernel::error::Error;
+
 #[macro_use]
 mod macros;
 
-use crate::gpu::Chipset;
+use crate::gpu::{Architecture, Chipset};
 
 /* PMC */
 
 register!(NV_PMC_BOOT_0 @ 0x00000000, "Basic revision information about the GPU" {
     3:0     minor_revision as u8, "Minor revision of the chip";
     7:4     major_revision as u8, "Major revision of the chip";
-    28:20   chipset as u32 ?=> Chipset, "Chipset model";
+    8:8     architecture_1 as u8, "MSB of the architecture";
+    23:20   implementation as u8, "Implementation version of the architecture";
+    28:24   architecture_0 as u8, "Lower bits of the architecture";
 });
+
+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, Error> {
+        Architecture::try_from(
+            self.architecture_0() | (self.architecture_1() << Self::ARCHITECTURE_0.len()),
+        )
+    }
+
+    /// Combines `architecture` and `implementation` to obtain a code unique to the chipset.
+    pub(crate) fn chipset(self) -> Result<Chipset, Error> {
+        self.architecture()
+            .map(|arch| {
+                ((arch as u32) << Self::IMPLEMENTATION.len()) | self.implementation() as u32
+            })
+            .and_then(Chipset::try_from)
+    }
+}

-- 
2.49.0