[PATCH v1 2/7] gpu: nova-core: allocate PCI MSI vector during probe

[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.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs       |  7 +++++++
 drivers/gpu/nova-core/irq.rs       | 25 +++++++++++++++++++++++++
 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 659f6a24ee13..3ac9cb106bfd 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -11,6 +11,8 @@
     sync::Arc, //
 };
 
+use crate::irq;
+
 use crate::{
     bounded_enum,
     driver::Bar0,
@@ -293,6 +295,11 @@ pub(crate) fn new<'a>(
 
             _: { gsp.boot(pdev, bar, spec.chipset, gsp_falcon, sec2_falcon)? },
 
+            // Allocate a PCI interrupt vector.
+            _: {
+                let _irq_vector = irq::alloc_vector(pdev)?;
+            },
+
             bar: devres_bar,
         })
     }
diff --git a/drivers/gpu/nova-core/irq.rs b/drivers/gpu/nova-core/irq.rs
new file mode 100644
index 000000000000..3a2a40519f11
--- /dev/null
+++ b/drivers/gpu/nova-core/irq.rs
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+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))?
+        }
+    };
+
+    Ok(*irq_vectors.start())
+}
diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
index 3a609f6937e4..837aa2d36a0e 100644
--- a/drivers/gpu/nova-core/nova_core.rs
+++ b/drivers/gpu/nova-core/nova_core.rs
@@ -19,6 +19,7 @@
 mod firmware;
 mod gpu;
 mod gsp;
+mod irq;
 #[macro_use]
 mod num;
 mod regs;
-- 
2.34.1