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 <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[ Use Result from kernel::prelude. - Danilo ]
Signed-off-by: Danilo Krummrich <[email protected]>

Author: Gnurou

drivers/gpu/nova-core/gpu.rs

@@ -101,9 +101,22 @@ impl fmt::Display for Chipset {
 /// 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) -> Result<Self> {
+        match value {
+            0x16 => Ok(Self::Turing),
+            0x17 => Ok(Self::Ampere),
+            0x19 => Ok(Self::Ada),
+            _ => Err(ENODEV),
+        }
+    }
 }
 
 pub(crate) struct Revision {

drivers/gpu/nova-core/regs.rs

@@ -7,12 +7,33 @@
 #[macro_use]
 mod macros;
 
-use crate::gpu::Chipset;
+use crate::gpu::{Architecture, Chipset};
+use kernel::prelude::*;
 
 /* 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> {
+        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> {
+        self.architecture()
+            .map(|arch| {
+                ((arch as u32) << Self::IMPLEMENTATION.len()) | self.implementation() as u32
+            })
+            .and_then(Chipset::try_from)
+    }
+}