linux-kernel - [PATCH v3 11/19] gpu: nova-core: register sysmem flush page

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Message-Id: <20250507-nova-frts-v3-11-fcb02749754d@nvidia.com>
Date: Wed, 07 May 2025 22:52:38 +0900
From: Alexandre Courbot <acourbot@...dia.com>
To: 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 <benno.lossin@...ton.me>, 
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
 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>, 
 Jonathan Corbet <corbet@....net>
Cc: John Hubbard <jhubbard@...dia.com>, Ben Skeggs <bskeggs@...dia.com>, 
 Joel Fernandes <joelagnelf@...dia.com>, Timur Tabi <ttabi@...dia.com>, 
 Alistair Popple <apopple@...dia.com>, linux-kernel@...r.kernel.org, 
 rust-for-linux@...r.kernel.org, nouveau@...ts.freedesktop.org, 
 dri-devel@...ts.freedesktop.org, Alexandre Courbot <acourbot@...dia.com>
Subject: [PATCH v3 11/19] gpu: nova-core: register sysmem flush page

A page of system memory is reserved so sysmembar can perform a read on
it if a system write occurred since the last flush. Do this early as it
can be required to e.g. reset the GPU falcons.

Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
---
 drivers/gpu/nova-core/gpu.rs  | 45 +++++++++++++++++++++++++++++++++++++++++--
 drivers/gpu/nova-core/regs.rs | 10 ++++++++++
 2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index a9fcf74717791dc7e23678869bf84f61e51873e2..c338da69ecbc2200f1ef3061a4d62971b021e3eb 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -3,6 +3,7 @@
 use kernel::{device, devres::Devres, error::code::*, pci, prelude::*};
 
 use crate::devinit;
+use crate::dma::DmaObject;
 use crate::driver::Bar0;
 use crate::firmware::Firmware;
 use crate::regs;
@@ -158,12 +159,32 @@ fn new(bar: &Bar0) -> Result<Spec> {
 }
 
 /// Structure holding the resources required to operate the GPU.
-#[pin_data]
+#[pin_data(PinnedDrop)]
 pub(crate) struct Gpu {
     spec: Spec,
     /// MMIO mapping of PCI BAR 0
     bar: Devres<Bar0>,
     fw: Firmware,
+    // System memory page required for flushing all pending GPU-side memory writes done through
+    // PCIE into system memory.
+    sysmem_flush: DmaObject,
+}
+
+#[pinned_drop]
+impl PinnedDrop for Gpu {
+    fn drop(self: Pin<&mut Self>) {
+        // Unregister the sysmem flush page before we release it.
+        let _ = self.bar.try_access_with(|b| {
+            regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR::default()
+                .set_adr_39_08(0)
+                .write(b);
+            if self.spec.chipset >= Chipset::GA102 {
+                regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR_HI::default()
+                    .set_adr_63_40(0)
+                    .write(b);
+            }
+        });
+    }
 }
 
 impl Gpu {
@@ -187,10 +208,30 @@ pub(crate) fn new(
         devinit::wait_gfw_boot_completion(bar)
             .inspect_err(|_| dev_err!(pdev.as_ref(), "GFW boot did not complete"))?;
 
+        // System memory page required for sysmembar to properly flush into system memory.
+        let sysmem_flush = {
+            let page = DmaObject::new(pdev.as_ref(), kernel::bindings::PAGE_SIZE)?;
+
+            // Register the sysmem flush page.
+            let handle = page.dma_handle();
+
+            regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR::default()
+                .set_adr_39_08((handle >> 8) as u32)
+                .write(bar);
+            if spec.chipset >= Chipset::GA102 {
+                regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR_HI::default()
+                    .set_adr_63_40((handle >> 40) as u32)
+                    .write(bar);
+            }
+
+            page
+        };
+
         Ok(pin_init!(Self {
             spec,
             bar: devres_bar,
-            fw
+            fw,
+            sysmem_flush,
         }))
     }
 }
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 401d885539cee03cbe732102f5e2233785a7b284..218cb6441eb0e5c6e5b52eabba006163eec0c8b4 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -39,6 +39,16 @@ pub(crate) fn chipset(self) -> Result<Chipset, Error> {
     }
 }
 
+/* PFB */
+
+register!(NV_PFB_NISO_FLUSH_SYSMEM_ADDR @ 0x00100c10 {
+    31:0    adr_39_08 as u32;
+});
+
+register!(NV_PFB_NISO_FLUSH_SYSMEM_ADDR_HI @ 0x00100c40 {
+    23:0    adr_63_40 as u32;
+});
+
 /* PGC6 */
 
 register!(NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_PRIV_LEVEL_MASK @ 0x00118128 {

-- 
2.49.0