[PATCH 07/12] gpu: nova-core: mm: Add the memory management HAL

Positioning the PRAMIN window requires writing an architecture-specific
register: `NV_PBUS_BAR0_WINDOW` on Turing, Ampere and Ada, and
`NV_XAL_EP_BAR0_WINDOW` with a different field width on Hopper and on
Blackwell.

A `MmHal` trait with one implementation per hardware family hides the
register choice from the rest of the mm code, matching the layout of
the driver's other HALs.

Signed-off-by: Eliot Courtney <[email protected]>
---
 drivers/gpu/nova-core/mm.rs           |  1 +
 drivers/gpu/nova-core/mm/hal.rs       | 56 +++++++++++++++++++++++++++++++++++
 drivers/gpu/nova-core/mm/hal/gb100.rs | 35 ++++++++++++++++++++++
 drivers/gpu/nova-core/mm/hal/gh100.rs | 35 ++++++++++++++++++++++
 drivers/gpu/nova-core/mm/hal/tu102.rs | 37 +++++++++++++++++++++++
 5 files changed, 164 insertions(+)

diff --git a/drivers/gpu/nova-core/mm.rs b/drivers/gpu/nova-core/mm.rs
index 7d24ad790310..07dce4ce2473 100644
--- a/drivers/gpu/nova-core/mm.rs
+++ b/drivers/gpu/nova-core/mm.rs
@@ -19,6 +19,7 @@
     },
 };
 
+mod hal;
 mod regs;
 
 /// Physical VRAM address in GPU video memory.
diff --git a/drivers/gpu/nova-core/mm/hal.rs b/drivers/gpu/nova-core/mm/hal.rs
new file mode 100644
index 000000000000..e7fd1e38bd38
--- /dev/null
+++ b/drivers/gpu/nova-core/mm/hal.rs
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+//! Memory management HAL.
+
+use kernel::{
+    num::Bounded,
+    prelude::*, //
+};
+
+use crate::{
+    driver::Bar0,
+    gpu::{
+        Architecture,
+        Chipset, //
+    },
+    mm::VramAddress, //
+};
+
+mod gb100;
+mod gh100;
+mod tu102;
+
+/// Trait implemented by per-architecture MM HALs.
+///
+/// `Sync` is required so that the `&'static dyn MmHal` references can be stored in `Send`
+/// structures.
+pub(super) trait MmHal: Sync {
+    /// Positions the PRAMIN window at `base`.
+    ///
+    /// This fails if `base` is not aligned to the 64 KiB window alignment or is too large for
+    /// the receiving register.
+    fn write_pramin_window_base(&self, bar: Bar0<'_>, base: VramAddress) -> Result;
+}
+
+/// Returns the HAL corresponding to `chipset`.
+pub(super) fn mm_hal(chipset: Chipset) -> &'static dyn MmHal {
+    match chipset.arch() {
+        Architecture::Turing | Architecture::Ampere | Architecture::Ada => tu102::TU102_HAL,
+        Architecture::Hopper => gh100::GH100_HAL,
+        Architecture::BlackwellGB10x | Architecture::BlackwellGB20x => gb100::GB100_HAL,
+    }
+}
+
+/// Converts `base` into the value of the window-base register field.
+///
+/// Fails with [`EINVAL`] if `base` is not aligned to the window alignment required by the register
+/// field's shift, or if the shifted value does not fit within `RES` bits.
+fn window_base<const RES: u32>(base: VramAddress) -> Result<Bounded<u64, RES>> {
+    const WINDOW_BASE_SHIFT: u32 = 16;
+
+    Bounded::<u64, 64>::from(base.into_raw())
+        .shr_exact::<WINDOW_BASE_SHIFT, { 64 - WINDOW_BASE_SHIFT }>()
+        .and_then(Bounded::try_shrink)
+        .ok_or(EINVAL)
+}
diff --git a/drivers/gpu/nova-core/mm/hal/gb100.rs b/drivers/gpu/nova-core/mm/hal/gb100.rs
new file mode 100644
index 000000000000..3781e143dea7
--- /dev/null
+++ b/drivers/gpu/nova-core/mm/hal/gb100.rs
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+//! Blackwell GB10x/GB20x memory management HAL.
+
+use kernel::{
+    io::Io,
+    prelude::*, //
+};
+
+use crate::{
+    driver::Bar0,
+    mm::{
+        hal::{
+            window_base,
+            MmHal, //
+        },
+        regs,
+        VramAddress, //
+    },
+};
+
+struct Gb100;
+
+impl MmHal for Gb100 {
+    fn write_pramin_window_base(&self, bar: Bar0<'_>, base: VramAddress) -> Result {
+        bar.write_reg(
+            regs::gb100::NV_XAL_EP_BAR0_WINDOW::zeroed().with_base(window_base(base)?.cast()),
+        );
+        Ok(())
+    }
+}
+
+const GB100: Gb100 = Gb100;
+pub(super) const GB100_HAL: &dyn MmHal = &GB100;
diff --git a/drivers/gpu/nova-core/mm/hal/gh100.rs b/drivers/gpu/nova-core/mm/hal/gh100.rs
new file mode 100644
index 000000000000..8af384db2921
--- /dev/null
+++ b/drivers/gpu/nova-core/mm/hal/gh100.rs
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+//! Hopper memory management HAL.
+
+use kernel::{
+    io::Io,
+    prelude::*, //
+};
+
+use crate::{
+    driver::Bar0,
+    mm::{
+        hal::{
+            window_base,
+            MmHal, //
+        },
+        regs,
+        VramAddress, //
+    },
+};
+
+struct Gh100;
+
+impl MmHal for Gh100 {
+    fn write_pramin_window_base(&self, bar: Bar0<'_>, base: VramAddress) -> Result {
+        bar.write_reg(
+            regs::gh100::NV_XAL_EP_BAR0_WINDOW::zeroed().with_base(window_base(base)?.cast()),
+        );
+        Ok(())
+    }
+}
+
+const GH100: Gh100 = Gh100;
+pub(super) const GH100_HAL: &dyn MmHal = &GH100;
diff --git a/drivers/gpu/nova-core/mm/hal/tu102.rs b/drivers/gpu/nova-core/mm/hal/tu102.rs
new file mode 100644
index 000000000000..e4fe7561223c
--- /dev/null
+++ b/drivers/gpu/nova-core/mm/hal/tu102.rs
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+//! Turing, Ampere and Ada memory management HAL.
+
+use kernel::{
+    io::Io,
+    prelude::*, //
+};
+
+use crate::{
+    driver::Bar0,
+    mm::{
+        hal::{
+            window_base,
+            MmHal, //
+        },
+        regs,
+        VramAddress, //
+    },
+};
+
+struct Tu102;
+
+impl MmHal for Tu102 {
+    fn write_pramin_window_base(&self, bar: Bar0<'_>, base: VramAddress) -> Result {
+        bar.write_reg(
+            regs::NV_PBUS_BAR0_WINDOW::zeroed()
+                .with_target(regs::Bar0WindowTarget::VidMem)
+                .with_base(window_base(base)?.cast()),
+        );
+        Ok(())
+    }
+}
+
+const TU102: Tu102 = Tu102;
+pub(super) const TU102_HAL: &dyn MmHal = &TU102;

-- 
2.55.0