gpu: nova-core: firmware: gsp: use dma::Coherent for level0 table

Replace the nova-core local `DmaObject` with a `CoherentBox` that can
fulfill the same role.

Since `CoherentBox` is more flexible than `DmaObject`, we can use the
native `u64` type for page table entries instead of messing with bytes.

The `dma` module becomes unused with that change, so remove it as well.

Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260327-b4-nova-dma-removal-v2-7-616e1d0b5cb3@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

3 files changed, 12 insertions, 64 deletions

diff --git a/drivers/gpu/nova-core/dma.rs b/drivers/gpu/nova-core/dma.rs
deleted file mode 100644
index 3c19d5ffcfe8..000000000000
--- a/drivers/gpu/nova-core/dma.rs
+++ /dev/null
@@ -1,53 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-//! Simple DMA object wrapper.
-
-use core::ops::{
-    Deref,
-    DerefMut, //
-};
-
-use kernel::{
-    device,
-    dma::Coherent,
-    page::PAGE_SIZE,
-    prelude::*, //
-};
-
-pub(crate) struct DmaObject {
-    dma: Coherent<[u8]>,
-}
-
-impl DmaObject {
-    pub(crate) fn new(dev: &device::Device<device::Bound>, len: usize) -> Result<Self> {
-        let len = core::alloc::Layout::from_size_align(len, PAGE_SIZE)
-            .map_err(|_| EINVAL)?
-            .pad_to_align()
-            .size();
-        let dma = Coherent::zeroed_slice(dev, len, GFP_KERNEL)?;
-
-        Ok(Self { dma })
-    }
-
-    pub(crate) fn from_data(dev: &device::Device<device::Bound>, data: &[u8]) -> Result<Self> {
-        let dma_obj = Self::new(dev, data.len())?;
-        // SAFETY: We have just allocated the DMA memory, we are the only users and
-        // we haven't made the device aware of the handle yet.
-        unsafe { dma_obj.as_mut()[..data.len()].copy_from_slice(data) };
-        Ok(dma_obj)
-    }
-}
-
-impl Deref for DmaObject {
-    type Target = Coherent<[u8]>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.dma
-    }
-}
-
-impl DerefMut for DmaObject {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.dma
-    }
-}
diff --git a/drivers/gpu/nova-core/firmware/gsp.rs b/drivers/gpu/nova-core/firmware/gsp.rs
index 1e0d545a74fe..86fb3f074195 100644
--- a/drivers/gpu/nova-core/firmware/gsp.rs
+++ b/drivers/gpu/nova-core/firmware/gsp.rs
@@ -4,10 +4,10 @@ use kernel::{
     device,
     dma::{
         Coherent,
+        CoherentBox,
         DataDirection,
         DmaAddress, //
     },
-    kvec,
     prelude::*,
     scatterlist::{
         Owned,
@@ -16,7 +16,6 @@ use kernel::{
 };
 
 use crate::{
-    dma::DmaObject,
     firmware::riscv::RiscvFirmware,
     gpu::{
         Architecture,
@@ -137,7 +136,7 @@ pub(crate) struct GspFirmware {
     #[pin]
     level1: SGTable<Owned<VVec<u8>>>,
     /// Level 0 page table (single 4KB page) with one entry: DMA address of first level 1 page.
-    level0: DmaObject,
+    level0: Coherent<[u64]>,
     /// Size in bytes of the firmware contained in [`Self::fw`].
     pub(crate) size: usize,
     /// Device-mapped GSP signatures matching the GPU's [`Chipset`].
@@ -198,17 +197,20 @@ impl GspFirmware {
                     // Allocate the level 0 page table as a device-visible DMA object, and map the
                     // level 1 page table onto it.
 
-                    // Level 0 page table data.
-                    let mut level0_data = kvec![0u8; GSP_PAGE_SIZE]?;
-
                     // Fill level 1 page entry.
                     let level1_entry = level1.iter().next().ok_or(EINVAL)?;
                     let level1_entry_addr = level1_entry.dma_address();
-                    let dst = &mut level0_data[..size_of_val(&level1_entry_addr)];
-                    dst.copy_from_slice(&level1_entry_addr.to_le_bytes());
 
-                    // Turn the level0 page table into a [`DmaObject`].
-                    DmaObject::from_data(dev, &level0_data)?
+                    // Create level 0 page table data and fill its first entry with the level 1
+                    // table.
+                    let mut level0 = CoherentBox::<[u64]>::zeroed_slice(
+                        dev,
+                        GSP_PAGE_SIZE / size_of::<u64>(),
+                        GFP_KERNEL
+                    )?;
+                    level0[0] = level1_entry_addr.to_le();
+
+                    level0.into()
                 },
                 size,
                 signatures: {
diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
index 98675c69d2b7..04a1fa6b25f8 100644
--- a/drivers/gpu/nova-core/nova_core.rs
+++ b/drivers/gpu/nova-core/nova_core.rs
@@ -13,7 +13,6 @@ use kernel::{
 #[macro_use]
 mod bitfield;
 
-mod dma;
 mod driver;
 mod falcon;
 mod fb;