[PATCH v8 02/16] gpu: nova-core: Set correct DMA mask

Alexandre Courbot
2025-11-07T23:43:03Z

From: Alistair Popple <apopple at nvidia.com>

Set the correct DMA mask. Without this DMA will fail on some setups.

Signed-off-by: Alistair Popple <apopple at nvidia.com>
Signed-off-by: Alexandre Courbot <acourbot at nvidia.com>
---
 drivers/gpu/nova-core/driver.rs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
index 2509f75eccb9..d91bbc50cde7 100644
--- a/drivers/gpu/nova-core/driver.rs
+++ b/drivers/gpu/nova-core/driver.rs
@@ -4,6 +4,8 @@
     auxiliary,
     c_str,
     device::Core,
+    dma::Device,
+    dma::DmaMask,
     pci,
     pci::{
         Class,
@@ -25,6 +27,15 @@ pub(crate) struct NovaCore {
 }

 const BAR0_SIZE: usize = SZ_16M;
+
+// For now we only support Ampere which can use up to 47-bit DMA addresses.
+//
+// TODO: Add an abstraction for this to support newer GPUs which may support
+// larger DMA addresses. Limiting these GPUs to smaller address widths
won't
+// have any adverse affects, unless installed on systems which require larger
+// DMA addresses. These systems should be quite rare.
+const GPU_DMA_BITS: u32 = 47;
+
 pub(crate) type Bar0 = pci::Bar<BAR0_SIZE>;

 kernel::pci_device_table!(
@@ -62,6 +73,11 @@ fn probe(pdev: &pci::Device<Core>, _info:
&Self::IdInfo) -> Result<Pin<KBox<Self
         pdev.enable_device_mem()?;
         pdev.set_master();

+        // SAFETY: No concurrent DMA allocations or mappings can be made
because
+        // the device is still being probed and therefore isn't being used
by
+        // other threads of execution.
+        unsafe {
pdev.dma_set_mask_and_coherent(DmaMask::new::<GPU_DMA_BITS>())? };
+
         let devres_bar = Arc::pin_init(
             pdev.iomap_region_sized::<BAR0_SIZE>(0,
c_str!("nova-core/bar0")),
             GFP_KERNEL,

--
2.51.2