Message-ID: <20251013062041.1639529-3-apopple@nvidia.com>
Date: Mon, 13 Oct 2025 17:20:28 +1100
From: Alistair Popple <apopple@...dia.com>
To: rust-for-linux@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	dakr@...nel.org,
	acourbot@...dia.com
Cc: Alistair Popple <apopple@...dia.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	John Hubbard <jhubbard@...dia.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Timur Tabi <ttabi@...dia.com>,
	linux-kernel@...r.kernel.org,
	nouveau@...ts.freedesktop.org
Subject: [PATCH v5 02/14] gpu: nova-core: Create initial Gsp

The GSP requires several areas of memory to operate. Each of these have
their own simple embedded page tables. Set these up and map them for DMA
to/from GSP using CoherentAllocation's. Return the DMA handle describing
where each of these regions are for future use when booting GSP.

Signed-off-by: Alistair Popple <apopple@...dia.com>

---

Changes for v5:
 - Move GSP_HEAP_ALIGNMENT to gsp/fw.rs and add a comment.
 - Create a LogBuffer type.
 - Use checked_add to ensure PTE values don't overflow.
 - Added some type documentation (shamelessly stolen from Nouveau)

Change for v3:
 - Clean up the PTE array creation, with much thanks to Alex for doing
   most it (please let me know if I should put you as co-developer!)

Changes for v2:
 - Renamed GspMemOjbects to Gsp as that is what they are
 - Rebased on Alex's latest series
---
 drivers/gpu/nova-core/gpu.rs                  |   2 +-
 drivers/gpu/nova-core/gsp.rs                  | 106 ++++++++++++++++--
 drivers/gpu/nova-core/gsp/fw.rs               |  64 ++++++++++-
 .../gpu/nova-core/gsp/fw/r570_144/bindings.rs |  19 ++++
 4 files changed, 179 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index ea124d1912e7..c1396775e9b6 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -197,7 +197,7 @@ pub(crate) fn new<'a>(
 
             sec2_falcon: Falcon::new(pdev.as_ref(), spec.chipset, bar, true)?,
 
-            gsp <- Gsp::new(),
+            gsp <- Gsp::new(pdev)?,
 
             _: { gsp.boot(pdev, bar, spec.chipset, gsp_falcon, sec2_falcon)? },
 
diff --git a/drivers/gpu/nova-core/gsp.rs b/drivers/gpu/nova-core/gsp.rs
index 221281da1a45..f1727173bd42 100644
--- a/drivers/gpu/nova-core/gsp.rs
+++ b/drivers/gpu/nova-core/gsp.rs
@@ -2,25 +2,117 @@
 
 mod boot;
 
+use kernel::device;
+use kernel::dma::CoherentAllocation;
+use kernel::dma::DmaAddress;
+use kernel::dma_write;
+use kernel::pci;
 use kernel::prelude::*;
-use kernel::ptr::Alignment;
+use kernel::transmute::AsBytes;
 
 pub(crate) use fw::{GspFwWprMeta, LibosParams};
 
 mod fw;
 
+use fw::LibosMemoryRegionInitArgument;
+
 pub(crate) const GSP_PAGE_SHIFT: usize = 12;
 pub(crate) const GSP_PAGE_SIZE: usize = 1 << GSP_PAGE_SHIFT;
-pub(crate) const GSP_HEAP_ALIGNMENT: Alignment = Alignment::new::<{ 1 << 20 }>();
+
+/// Number of GSP pages to use in a RM log buffer.
+const RM_LOG_BUFFER_NUM_PAGES: usize = 0x10;
 
 /// GSP runtime data.
-///
-/// This is an empty pinned placeholder for now.
 #[pin_data]
-pub(crate) struct Gsp {}
+pub(crate) struct Gsp {
+    pub(crate) libos: CoherentAllocation<LibosMemoryRegionInitArgument>,
+    loginit: LogBuffer,
+    logintr: LogBuffer,
+    logrm: LogBuffer,
+}
+
+#[repr(C)]
+struct PteArray<const NUM_ENTRIES: usize>([u64; NUM_ENTRIES]);
+
+/// SAFETY: arrays of `u64` implement `AsBytes` and we are but a wrapper around it.
+unsafe impl<const NUM_ENTRIES: usize> AsBytes for PteArray<NUM_ENTRIES> {}
+
+impl<const NUM_PAGES: usize> PteArray<NUM_PAGES> {
+    fn new(handle: DmaAddress) -> Result<Self> {
+        let mut ptes = [0u64; NUM_PAGES];
+        for (i, pte) in ptes.iter_mut().enumerate() {
+            *pte = handle
+                .checked_add((i as u64) << GSP_PAGE_SHIFT)
+                .ok_or(EOVERFLOW)?;
+        }
+
+        Ok(Self(ptes))
+    }
+}
+
+/// The logging buffers are byte queues that contain encoded printf-like
+/// messages from GSP-RM.  They need to be decoded by a special application
+/// that can parse the buffers.
+///
+/// The 'loginit' buffer contains logs from early GSP-RM init and
+/// exception dumps.  The 'logrm' buffer contains the subsequent logs. Both are
+/// written to directly by GSP-RM and can be any multiple of GSP_PAGE_SIZE.
+///
+/// The physical address map for the log buffer is stored in the buffer
+/// itself, starting with offset 1. Offset 0 contains the "put" pointer (pp).
+/// Initially, pp is equal to 0. If the buffer has valid logging data in it,
+/// then pp points to index into the buffer where the next logging entry will
+/// be written. Therefore, the logging data is valid if:
+///   1 <= pp < sizeof(buffer)/sizeof(u64)
+struct LogBuffer(CoherentAllocation<u8>);
+
+impl LogBuffer {
+    fn new(dev: &device::Device<device::Bound>) -> Result<Self> {
+        const NUM_PAGES: usize = RM_LOG_BUFFER_NUM_PAGES;
+
+        let mut obj = Self(CoherentAllocation::<u8>::alloc_coherent(
+            dev,
+            NUM_PAGES * GSP_PAGE_SIZE,
+            GFP_KERNEL | __GFP_ZERO,
+        )?);
+        let ptes = PteArray::<NUM_PAGES>::new(obj.0.dma_handle())?;
+
+        // SAFETY: `obj` has just been created and we are its sole user.
+        unsafe {
+            // Copy the self-mapping PTE at the expected location.
+            obj.0
+                .as_slice_mut(size_of::<u64>(), size_of_val(&ptes))?
+                .copy_from_slice(ptes.as_bytes())
+        };
+
+        Ok(obj)
+    }
+}
 
 impl Gsp {
-    pub(crate) fn new() -> impl PinInit<Self> {
-        pin_init!(Self {})
+    pub(crate) fn new(pdev: &pci::Device<device::Bound>) -> Result<impl PinInit<Self, Error>> {
+        let dev = pdev.as_ref();
+        let libos = CoherentAllocation::<LibosMemoryRegionInitArgument>::alloc_coherent(
+            dev,
+            GSP_PAGE_SIZE / size_of::<LibosMemoryRegionInitArgument>(),
+            GFP_KERNEL | __GFP_ZERO,
+        )?;
+
+        // Initialise the logging structures. The OpenRM equivalents are in:
+        // _kgspInitLibosLoggingStructures (allocates memory for buffers)
+        // kgspSetupLibosInitArgs_IMPL (creates pLibosInitArgs[] array)
+        let loginit = LogBuffer::new(dev)?;
+        dma_write!(libos[0] = LibosMemoryRegionInitArgument::new("LOGINIT", &loginit.0)?)?;
+        let logintr = LogBuffer::new(dev)?;
+        dma_write!(libos[1] = LibosMemoryRegionInitArgument::new("LOGINTR", &logintr.0)?)?;
+        let logrm = LogBuffer::new(dev)?;
+        dma_write!(libos[2] = LibosMemoryRegionInitArgument::new("LOGRM", &logrm.0)?)?;
+
+        Ok(try_pin_init!(Self {
+            libos,
+            loginit,
+            logintr,
+            logrm,
+        }))
     }
 }
diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index 181baa401770..c3bececc29cd 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -7,15 +7,20 @@
 
 use core::ops::Range;
 
-use kernel::ptr::Alignable;
+use kernel::dma::CoherentAllocation;
+use kernel::prelude::*;
+use kernel::ptr::{Alignable, Alignment};
 use kernel::sizes::SZ_1M;
+use kernel::transmute::{AsBytes, FromBytes};
 
 use crate::gpu::Chipset;
-use crate::gsp;
 
 /// Dummy type to group methods related to heap parameters for running the GSP firmware.
 pub(crate) struct GspFwHeapParams(());
 
+/// Minimum required alignment for the GSP heap.
+const GSP_HEAP_ALIGNMENT: Alignment = Alignment::new::<{ 1 << 20 }>();
+
 impl GspFwHeapParams {
     /// Returns the amount of GSP-RM heap memory used during GSP-RM boot and initialization (up to
     /// and including the first client subdevice allocation).
@@ -29,7 +34,7 @@ fn base_rm_size(_chipset: Chipset) -> u64 {
     /// Returns the amount of heap memory required to support a single channel allocation.
     fn client_alloc_size() -> u64 {
         u64::from(bindings::GSP_FW_HEAP_PARAM_CLIENT_ALLOC_SIZE)
-            .align_up(gsp::GSP_HEAP_ALIGNMENT)
+            .align_up(GSP_HEAP_ALIGNMENT)
             .unwrap_or(u64::MAX)
     }
 
@@ -40,7 +45,7 @@ fn management_overhead(fb_size: u64) -> u64 {
 
         u64::from(bindings::GSP_FW_HEAP_PARAM_SIZE_PER_GB_FB)
             .saturating_mul(fb_size_gb)
-            .align_up(gsp::GSP_HEAP_ALIGNMENT)
+            .align_up(GSP_HEAP_ALIGNMENT)
             .unwrap_or(u64::MAX)
     }
 }
@@ -99,3 +104,54 @@ pub(crate) fn wpr_heap_size(&self, chipset: Chipset, fb_size: u64) -> u64 {
 /// addresses of the GSP bootloader and firmware.
 #[repr(transparent)]
 pub(crate) struct GspFwWprMeta(bindings::GspFwWprMeta);
+
+/// Struct containing the arguments required to pass a memory buffer to the GSP
+/// for use during initialisation.
+///
+/// The GSP only understands 4K pages (GSP_PAGE_SIZE), so even if the kernel is
+/// configured for a larger page size (e.g. 64K pages), we need to give
+/// the GSP an array of 4K pages. Since we only create physically contiguous
+/// buffers the math to calculate the addresses is simple.
+///
+/// The buffers must be a multiple of GSP_PAGE_SIZE.  GSP-RM also currently
+/// ignores the @kind field for LOGINIT, LOGINTR, and LOGRM, but expects the
+/// buffers to be physically contiguous anyway.
+///
+/// The memory allocated for the arguments must remain until the GSP sends the
+/// init_done RPC.
+#[repr(transparent)]
+pub(crate) struct LibosMemoryRegionInitArgument(bindings::LibosMemoryRegionInitArgument);
+
+// SAFETY: Padding is explicit and will not contain uninitialized data.
+unsafe impl AsBytes for LibosMemoryRegionInitArgument {}
+
+// SAFETY: This struct only contains integer types for which all bit patterns
+// are valid.
+unsafe impl FromBytes for LibosMemoryRegionInitArgument {}
+
+impl LibosMemoryRegionInitArgument {
+    pub(crate) fn new<A: AsBytes + FromBytes>(
+        name: &'static str,
+        obj: &CoherentAllocation<A>,
+    ) -> Result<Self> {
+        /// Generates the `ID8` identifier required for some GSP objects.
+        fn id8(name: &str) -> u64 {
+            let mut bytes = [0u8; core::mem::size_of::<u64>()];
+
+            for (c, b) in name.bytes().rev().zip(&mut bytes) {
+                *b = c;
+            }
+
+            u64::from_ne_bytes(bytes)
+        }
+
+        Ok(Self(bindings::LibosMemoryRegionInitArgument {
+            id8: id8(name),
+            pa: obj.dma_handle(),
+            size: obj.size() as u64,
+            kind: bindings::LibosMemoryRegionKind_LIBOS_MEMORY_REGION_CONTIGUOUS.try_into()?,
+            loc: bindings::LibosMemoryRegionLoc_LIBOS_MEMORY_REGION_LOC_SYSMEM.try_into()?,
+            ..Default::default()
+        }))
+    }
+}
diff --git a/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs b/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
index 0407000cca22..6a14cc324391 100644
--- a/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
+++ b/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
@@ -124,3 +124,22 @@ fn default() -> Self {
         }
     }
 }
+pub type LibosAddress = u64_;
+pub const LibosMemoryRegionKind_LIBOS_MEMORY_REGION_NONE: LibosMemoryRegionKind = 0;
+pub const LibosMemoryRegionKind_LIBOS_MEMORY_REGION_CONTIGUOUS: LibosMemoryRegionKind = 1;
+pub const LibosMemoryRegionKind_LIBOS_MEMORY_REGION_RADIX3: LibosMemoryRegionKind = 2;
+pub type LibosMemoryRegionKind = ffi::c_uint;
+pub const LibosMemoryRegionLoc_LIBOS_MEMORY_REGION_LOC_NONE: LibosMemoryRegionLoc = 0;
+pub const LibosMemoryRegionLoc_LIBOS_MEMORY_REGION_LOC_SYSMEM: LibosMemoryRegionLoc = 1;
+pub const LibosMemoryRegionLoc_LIBOS_MEMORY_REGION_LOC_FB: LibosMemoryRegionLoc = 2;
+pub type LibosMemoryRegionLoc = ffi::c_uint;
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct LibosMemoryRegionInitArgument {
+    pub id8: LibosAddress,
+    pub pa: LibosAddress,
+    pub size: LibosAddress,
+    pub kind: u8_,
+    pub loc: u8_,
+    pub __bindgen_padding_0: [u8; 6usize],
+}
-- 
2.50.1

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