1 files changed, 147 insertions, 0 deletions
diff --git a/drivers/gpu/nova-core/fb.rs b/drivers/gpu/nova-core/fb.rs
new file mode 100644
index 000000000000..4a702525fff4
--- /dev/null
+++ b/drivers/gpu/nova-core/fb.rs
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use core::ops::Range;
+
+use kernel::prelude::*;
+use kernel::sizes::*;
+use kernel::types::ARef;
+use kernel::{dev_warn, device};
+
+use crate::dma::DmaObject;
+use crate::driver::Bar0;
+use crate::gpu::Chipset;
+use crate::regs;
+
+mod hal;
+
+/// Type holding the sysmem flush memory page, a page of memory to be written into the
+/// `NV_PFB_NISO_FLUSH_SYSMEM_ADDR*` registers and used to maintain memory coherency.
+///
+/// A system memory page is required for `sysmembar`, which is a GPU-initiated hardware
+/// memory-barrier operation that flushes all pending GPU-side memory writes that were done through
+/// PCIE to system memory. It is required for falcons to be reset as the reset operation involves a
+/// reset handshake. When the falcon acknowledges a reset, it writes into system memory. To ensure
+/// this write is visible to the host and prevent driver timeouts, the falcon must perform a
+/// sysmembar operation to flush its writes.
+///
+/// Because of this, the sysmem flush memory page must be registered as early as possible during
+/// driver initialization, and before any falcon is reset.
+///
+/// Users are responsible for manually calling [`Self::unregister`] before dropping this object,
+/// otherwise the GPU might still use it even after it has been freed.
+pub(crate) struct SysmemFlush {
+    /// Chipset we are operating on.
+    chipset: Chipset,
+    device: ARef<device::Device>,
+    /// Keep the page alive as long as we need it.
+    page: DmaObject,
+}
+
+impl SysmemFlush {
+    /// Allocate a memory page and register it as the sysmem flush page.
+    pub(crate) fn register(
+        dev: &device::Device<device::Bound>,
+        bar: &Bar0,
+        chipset: Chipset,
+    ) -> Result<Self> {
+        let page = DmaObject::new(dev, kernel::page::PAGE_SIZE)?;
+
+        hal::fb_hal(chipset).write_sysmem_flush_page(bar, page.dma_handle())?;
+
+        Ok(Self {
+            chipset,
+            device: dev.into(),
+            page,
+        })
+    }
+
+    /// Unregister the managed sysmem flush page.
+    ///
+    /// In order to gracefully tear down the GPU, users must make sure to call this method before
+    /// dropping the object.
+    pub(crate) fn unregister(&self, bar: &Bar0) {
+        let hal = hal::fb_hal(self.chipset);
+
+        if hal.read_sysmem_flush_page(bar) == self.page.dma_handle() {
+            let _ = hal.write_sysmem_flush_page(bar, 0).inspect_err(|e| {
+                dev_warn!(
+                    &self.device,
+                    "failed to unregister sysmem flush page: {:?}",
+                    e
+                )
+            });
+        } else {
+            // Another page has been registered after us for some reason - warn as this is a bug.
+            dev_warn!(
+                &self.device,
+                "attempt to unregister a sysmem flush page that is not active\n"
+            );
+        }
+    }
+}
+
+/// Layout of the GPU framebuffer memory.
+///
+/// Contains ranges of GPU memory reserved for a given purpose during the GSP boot process.
+#[derive(Debug)]
+#[expect(dead_code)]
+pub(crate) struct FbLayout {
+    pub(crate) fb: Range<u64>,
+    pub(crate) vga_workspace: Range<u64>,
+    pub(crate) frts: Range<u64>,
+}
+
+impl FbLayout {
+    /// Computes the FB layout.
+    pub(crate) fn new(chipset: Chipset, bar: &Bar0) -> Result<Self> {
+        let hal = hal::fb_hal(chipset);
+
+        let fb = {
+            let fb_size = hal.vidmem_size(bar);
+
+            0..fb_size
+        };
+
+        let vga_workspace = {
+            let vga_base = {
+                const NV_PRAMIN_SIZE: u64 = SZ_1M as u64;
+                let base = fb.end - NV_PRAMIN_SIZE;
+
+                if hal.supports_display(bar) {
+                    match regs::NV_PDISP_VGA_WORKSPACE_BASE::read(bar).vga_workspace_addr() {
+                        Some(addr) => {
+                            if addr < base {
+                                const VBIOS_WORKSPACE_SIZE: u64 = SZ_128K as u64;
+
+                                // Point workspace address to end of framebuffer.
+                                fb.end - VBIOS_WORKSPACE_SIZE
+                            } else {
+                                addr
+                            }
+                        }
+                        None => base,
+                    }
+                } else {
+                    base
+                }
+            };
+
+            vga_base..fb.end
+        };
+
+        let frts = {
+            const FRTS_DOWN_ALIGN: u64 = SZ_128K as u64;
+            const FRTS_SIZE: u64 = SZ_1M as u64;
+            // TODO[NUMM]: replace with `align_down` once it lands.
+            let frts_base = (vga_workspace.start & !(FRTS_DOWN_ALIGN - 1)) - FRTS_SIZE;
+
+            frts_base..frts_base + FRTS_SIZE
+        };
+
+        Ok(Self {
+            fb,
+            vga_workspace,
+            frts,
+        })
+    }
+}