[PATCH v3 05/14] gpu: nova-core: add the per-architecture GIN CPU interrupt HAL

[John Hubbard]

GIN, the GPU Interrupt and Notification unit, is the GPU's interrupt
controller. Each PCIe function has its own tree, whose leaf count
depends on the GPU family.

Message-signaled delivery stops after each edge until the CPU rearms it,
and the rearm write differs by family and interrupt type:

* Pre-Hopper MSI writes an EOI through the BAR0 PCI configuration space
  mirror.

* MSI for Hopper and later cycles the TOP enable bits of every serviced
  subtree.

* MSI-X on any family cycles the bits of the handler's own subtree.

Provide the leaf count and the rearm method through a per-architecture
interrupt HAL, and name the interrupt type with nova-core's own two
variants rather than the PCI core's three, which include the
level-triggered INTx that nova-core never allocates.

Assisted-by: Cursor:claude-opus-5
Reviewed-by: Will Pierce <wpierce@xxxxxxxxxx>
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 drivers/gpu/nova-core/irq.rs           |  14 ++++
 drivers/gpu/nova-core/irq/hal.rs       | 106 +++++++++++++++++++++++++
 drivers/gpu/nova-core/irq/hal/gh100.rs |  29 +++++++
 drivers/gpu/nova-core/irq/hal/tu102.rs |  28 +++++++
 4 files changed, 177 insertions(+)
 create mode 100644 drivers/gpu/nova-core/irq/hal.rs
 create mode 100644 drivers/gpu/nova-core/irq/hal/gh100.rs
 create mode 100644 drivers/gpu/nova-core/irq/hal/tu102.rs

diff --git a/drivers/gpu/nova-core/irq.rs b/drivers/gpu/nova-core/irq.rs
index 3066ceeb850c..d21dee1b89a0 100644
--- a/drivers/gpu/nova-core/irq.rs
+++ b/drivers/gpu/nova-core/irq.rs
@@ -8,5 +8,19 @@
 //!
 //! See `Documentation/gpu/nova/core/interrupts.rst`.
 
+mod hal;
 mod interrupt_tree;
 mod regs;
+
+/// The message-signaled interrupt type a vector allocation obtained.
+///
+/// nova-core allocates MSI-X or MSI and nothing else, so the level-triggered INTx that
+/// [`kernel::pci::IrqType`] also names has no representation here.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(crate) enum MsiType {
+    /// One message, raised by every subtree of the tree.
+    Msi,
+
+    /// One table entry per subtree.
+    MsiX,
+}
diff --git a/drivers/gpu/nova-core/irq/hal.rs b/drivers/gpu/nova-core/irq/hal.rs
new file mode 100644
index 000000000000..1ea677e37e56
--- /dev/null
+++ b/drivers/gpu/nova-core/irq/hal.rs
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+//! Per-architecture properties of the GIN CPU interrupt tree.
+
+mod gh100;
+mod tu102;
+
+use kernel::{
+    io::Io,
+    prelude::*, //
+};
+
+use crate::{
+    driver::Bar0,
+    gpu::{
+        Architecture,
+        Chipset, //
+    }, //
+};
+
+use super::{
+    interrupt_tree::{
+        LeafCount,
+        Subtree,
+        SubtreeSet, //
+    },
+    regs,
+    MsiType, //
+};
+
+/// Register write that restores PCI interrupt delivery to the CPU.
+///
+/// A message-signaled interrupt is delivered once per edge, and the PCI side delivers no further
+/// interrupt until the CPU rearms it. A handler that returns without this write receives no more
+/// interrupts.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(super) enum PciIrqRearmMethod {
+    /// The MSI end-of-interrupt register in the BAR0 PCI configuration-space mirror, used by
+    /// MSI on pre-Hopper GPUs.
+    ConfigMirrorEoi,
+
+    /// A clear then a set of the `TOP` enable bits of every serviced subtree, which produces the
+    /// edge that delivers the next interrupt.
+    ///
+    /// MSI has a single message that every subtree raises, so the rearm covers the whole serviced
+    /// set.
+    TopEnableCycleServiced,
+
+    /// The same enable cycle, restricted to the one subtree the handler serves.
+    ///
+    /// MSI-X gives each subtree its own table entry and its own handler.
+    TopEnableCycleSubtree,
+}
+
+impl PciIrqRearmMethod {
+    /// Performs this method's register write.
+    ///
+    /// `serviced` holds every subtree the driver services, and `subtree` is the one subtree the
+    /// calling handler serves. Each method uses whichever of the two its interrupt type delivers
+    /// on, so both are required.
+    pub(super) fn rearm(self, bar: Bar0<'_>, serviced: SubtreeSet, subtree: Subtree) {
+        let subtrees = match self {
+            // The written value is ignored, so any write rearms delivery.
+            Self::ConfigMirrorEoi => {
+                bar.write(regs::NV_XVE_CYA_2, 0u32.into());
+                return;
+            }
+            Self::TopEnableCycleServiced => serviced,
+            Self::TopEnableCycleSubtree => SubtreeSet::from(subtree),
+        };
+
+        bar.write_reg(
+            regs::NV_VIRTUAL_FUNCTION_PRIV_CPU_INTR_TOP_EN_CLEAR::zeroed().with_subtrees(subtrees),
+        );
+        bar.write_reg(
+            regs::NV_VIRTUAL_FUNCTION_PRIV_CPU_INTR_TOP_EN_SET::zeroed().with_subtrees(subtrees),
+        );
+    }
+}
+
+/// Per-architecture properties of the GIN CPU interrupt tree.
+///
+/// The tree size and the method that rearms PCI interrupt delivery differ by family.
+///
+/// See `Documentation/gpu/nova/core/interrupts.rst`.
+pub(super) trait CpuInterruptHal {
+    /// Returns the number of leaves the CPU tree implements.
+    ///
+    /// [`LeafCount::subtree_set`] gives the subtrees behind them, and
+    /// [`LeafCount::vector_count`] the vectors they carry.
+    fn leaf_count(&self) -> LeafCount;
+
+    /// Returns the method that rearms PCI interrupt delivery for `msi_type`.
+    fn pci_irq_rearm_method(&self, msi_type: MsiType) -> PciIrqRearmMethod;
+}
+
+/// Returns the [`CpuInterruptHal`] for `chipset`.
+pub(super) fn cpu_interrupt_hal(chipset: Chipset) -> &'static dyn CpuInterruptHal {
+    match chipset.arch() {
+        Architecture::Turing | Architecture::Ampere | Architecture::Ada => tu102::TU102_HAL,
+        Architecture::Hopper | Architecture::BlackwellGB10x | Architecture::BlackwellGB20x => {
+            gh100::GH100_HAL
+        }
+    }
+}
diff --git a/drivers/gpu/nova-core/irq/hal/gh100.rs b/drivers/gpu/nova-core/irq/hal/gh100.rs
new file mode 100644
index 000000000000..10744ac3ab77
--- /dev/null
+++ b/drivers/gpu/nova-core/irq/hal/gh100.rs
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+use super::{
+    CpuInterruptHal,
+    LeafCount,
+    MsiType,
+    PciIrqRearmMethod, //
+};
+
+/// GIN parameters for Hopper and Blackwell, which implement a 16-leaf CPU tree. Only 12 leaves
+/// carry sources.
+struct Gh100;
+
+impl CpuInterruptHal for Gh100 {
+    fn leaf_count(&self) -> LeafCount {
+        LeafCount::Sixteen
+    }
+
+    fn pci_irq_rearm_method(&self, msi_type: MsiType) -> PciIrqRearmMethod {
+        match msi_type {
+            MsiType::Msi => PciIrqRearmMethod::TopEnableCycleServiced,
+            MsiType::MsiX => PciIrqRearmMethod::TopEnableCycleSubtree,
+        }
+    }
+}
+
+const GH100: Gh100 = Gh100;
+pub(super) const GH100_HAL: &dyn CpuInterruptHal = &GH100;
diff --git a/drivers/gpu/nova-core/irq/hal/tu102.rs b/drivers/gpu/nova-core/irq/hal/tu102.rs
new file mode 100644
index 000000000000..fb8ded59c792
--- /dev/null
+++ b/drivers/gpu/nova-core/irq/hal/tu102.rs
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+use super::{
+    CpuInterruptHal,
+    LeafCount,
+    MsiType,
+    PciIrqRearmMethod, //
+};
+
+/// GIN parameters for Turing, Ampere, and Ada, which implement an 8-leaf CPU tree.
+struct Tu102;
+
+impl CpuInterruptHal for Tu102 {
+    fn leaf_count(&self) -> LeafCount {
+        LeafCount::Eight
+    }
+
+    fn pci_irq_rearm_method(&self, msi_type: MsiType) -> PciIrqRearmMethod {
+        match msi_type {
+            MsiType::Msi => PciIrqRearmMethod::ConfigMirrorEoi,
+            MsiType::MsiX => PciIrqRearmMethod::TopEnableCycleSubtree,
+        }
+    }
+}
+
+const TU102: Tu102 = Tu102;
+pub(super) const TU102_HAL: &dyn CpuInterruptHal = &TU102;
-- 
2.55.0