[PATCH 04/17] gpu: nova-core: allocate PCI MSI vector during probe

[John Hubbard <jhubbard@nvidia.com>]

From: Joel Fernandes <joelagnelf@nvidia.com>

Allocate a single PCI MSI interrupt vector in the probe path.

Try MSI/MSI-X first. If that fails (possible in broken VFIO setups),
fall back to INTx with a dev_warn so the issue is visible in dmesg.
The allocation is devres-managed and automatically freed on unbind.

Reviewed-by: Will Pierce <wpierce@nvidia.com>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs       |  6 ++++++
 drivers/gpu/nova-core/irq.rs       | 26 ++++++++++++++++++++++++++
 drivers/gpu/nova-core/nova_core.rs |  1 +
 3 files changed, 33 insertions(+)
 create mode 100644 drivers/gpu/nova-core/irq.rs

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 42a4cd7971fa..5efeba056f1b 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -29,6 +29,7 @@
         Gsp,
         GspBootContext, //
     },
+    irq,
     regs,
     vgpu::VgpuManager, //
 };
@@ -386,6 +387,11 @@ pub(crate) fn new(
                 })?,
             }),
 
+            // Allocate a PCI interrupt vector.
+            _: {
+                let _irq_vector = irq::alloc_vector(pdev)?;
+            },
+
             gsp_static_info: {
                 // Obtain and display basic GPU information.
                 let info = gsp_resources.gsp.get_static_info(bar)?;
diff --git a/drivers/gpu/nova-core/irq.rs b/drivers/gpu/nova-core/irq.rs
new file mode 100644
index 000000000000..48900c734cb6
--- /dev/null
+++ b/drivers/gpu/nova-core/irq.rs
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+use kernel::{
+    device::Bound,
+    pci::{
+        self,
+        IrqType,
+        IrqTypes, //
+    },
+    prelude::*,
+};
+
+pub(crate) fn alloc_vector(pdev: &pci::Device<Bound>) -> Result<pci::IrqVector<'_>> {
+    let msi_types = IrqTypes::default().with(IrqType::Msi).with(IrqType::MsiX);
+
+    let irq_vectors = match pdev.alloc_irq_vectors(1, 1, msi_types) {
+        Ok(vecs) => vecs,
+        Err(_) => {
+            dev_warn!(pdev.as_ref(), "MSI not available, falling back to INTx\n");
+            pdev.alloc_irq_vectors(1, 1, IrqTypes::default().with(IrqType::Intx))?
+        }
+    };
+
+    irq_vectors.vector(0)
+}
diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
index 35a8b1214b0e..68b5abfe494d 100644
--- a/drivers/gpu/nova-core/nova_core.rs
+++ b/drivers/gpu/nova-core/nova_core.rs
@@ -17,6 +17,7 @@
 mod fsp;
 mod gpu;
 mod gsp;
+mod irq;
 mod mctp;
 #[macro_use]
 mod num;
-- 
2.55.0