[PATCH v2 22/25] gpu: nova-core: use HRT lifetime for Bar

[Danilo Krummrich <dakr@kernel.org>]

Take advantage of the lifetime-parameterized pci::Bar<'bound> to hold
the BAR mapping directly in NovaCore<'bound>, and pass a borrowed
reference to Gpu<'bound>.

This eliminates the Arc<Devres<Bar0>> indirection, removes runtime
revocation checks for BAR access, and simplifies Gpu::unbind().

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 drivers/gpu/nova-core/driver.rs    | 40 ++++++++++++++----------------
 drivers/gpu/nova-core/gpu.rs       | 27 ++++++++------------
 drivers/gpu/nova-core/nova_core.rs |  2 +-
 3 files changed, 30 insertions(+), 39 deletions(-)

diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
index 6ee2021ef56e..11b632ae3789 100644
--- a/drivers/gpu/nova-core/driver.rs
+++ b/drivers/gpu/nova-core/driver.rs
@@ -14,12 +14,9 @@
     },
     prelude::*,
     sizes::SZ_16M,
-    sync::{
-        atomic::{
-            Atomic,
-            Relaxed, //
-        },
-        Arc,
+    sync::atomic::{
+        Atomic,
+        Relaxed, //
     },
     types::ForLt,
 };
@@ -30,9 +27,10 @@
 static AUXILIARY_ID_COUNTER: Atomic<u32> = Atomic::new(0);
 
 #[pin_data]
-pub(crate) struct NovaCore {
+pub(crate) struct NovaCore<'bound> {
     #[pin]
-    pub(crate) gpu: Gpu,
+    pub(crate) gpu: Gpu<'bound>,
+    bar: pci::Bar<'bound, BAR0_SIZE>,
     #[allow(clippy::type_complexity)]
     _reg: Devres<auxiliary::Registration<ForLt!(())>>,
 }
@@ -47,12 +45,12 @@ pub(crate) struct NovaCore {
 // DMA addresses. These systems should be quite rare.
 const GPU_DMA_BITS: u32 = 47;
 
-pub(crate) type Bar0 = pci::Bar<'static, BAR0_SIZE>;
+pub(crate) type Bar0 = kernel::io::Mmio<BAR0_SIZE>;
 
 kernel::pci_device_table!(
     PCI_TABLE,
     MODULE_PCI_TABLE,
-    <NovaCore as pci::Driver<'_>>::IdInfo,
+    <NovaCore<'_> as pci::Driver<'_>>::IdInfo,
     [
         // Modern NVIDIA GPUs will show up as either VGA or 3D controllers.
         (
@@ -74,7 +72,7 @@ pub(crate) struct NovaCore {
     ]
 );
 
-impl<'bound> pci::Driver<'bound> for NovaCore {
+impl<'bound> pci::Driver<'bound> for NovaCore<'bound> {
     type IdInfo = ();
     const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
 
@@ -93,14 +91,14 @@ fn probe(
             // other threads of execution.
             unsafe { pdev.dma_set_mask_and_coherent(DmaMask::new::<GPU_DMA_BITS>())? };
 
-            let bar = Arc::new(
-                pdev.iomap_region_sized::<BAR0_SIZE>(0, c"nova-core/bar0")?
-                    .into_devres()?,
-                GFP_KERNEL,
-            )?;
-
-            Ok(try_pin_init!(Self {
-                gpu <- Gpu::new(pdev, bar.clone(), bar.access(pdev.as_ref())?),
+            Ok(try_pin_init!(NovaCore {
+                bar: pdev.iomap_region_sized::<BAR0_SIZE>(0, c"nova-core/bar0")?,
+                // TODO: Use `&bar` self-referential pin-init syntax once available.
+                //
+                // SAFETY: `bar` is initialized before this expression is evaluated
+                // (`try_pin_init!()` initializes fields in declaration order), lives at a pinned
+                // stable address, and is dropped after `gpu` (struct field drop order).
+                gpu <- Gpu::new(pdev, unsafe { &*core::ptr::from_ref(bar) }),
                 _reg: auxiliary::Registration::new(
                     pdev.as_ref(),
                     c"nova-drm",
@@ -114,7 +112,7 @@ fn probe(
         })
     }
 
-    fn unbind(pdev: &pci::Device<Core>, this: Pin<&Self>) {
-        this.gpu.unbind(pdev.as_ref());
+    fn unbind(_pdev: &'bound pci::Device<Core>, this: Pin<&'bound Self>) {
+        this.gpu.unbind();
     }
 }
diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 9288b30fe4c3..03295fa6fb32 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -2,13 +2,11 @@
 
 use kernel::{
     device,
-    devres::Devres,
     fmt,
     io::Io,
     num::Bounded,
     pci,
-    prelude::*,
-    sync::Arc, //
+    prelude::*, //
 };
 
 use crate::{
@@ -224,10 +222,10 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 
 /// Structure holding the resources required to operate the GPU.
 #[pin_data]
-pub(crate) struct Gpu {
+pub(crate) struct Gpu<'bound> {
     spec: Spec,
-    /// MMIO mapping of PCI BAR 0
-    bar: Arc<Devres<Bar0>>,
+    /// MMIO mapping of PCI BAR 0.
+    bar: &'bound Bar0,
     /// System memory page required for flushing all pending GPU-side memory writes done through
     /// PCIE into system memory, via sysmembar (A GPU-initiated HW memory-barrier operation).
     sysmem_flush: SysmemFlush,
@@ -240,10 +238,9 @@ pub(crate) struct Gpu {
     gsp: Gsp,
 }
 
-impl Gpu {
-    pub(crate) fn new<'bound>(
+impl<'bound> Gpu<'bound> {
+    pub(crate) fn new(
         pdev: &'bound pci::Device<device::Bound>,
-        devres_bar: Arc<Devres<Bar0>>,
         bar: &'bound Bar0,
     ) -> impl PinInit<Self, Error> + 'bound {
         try_pin_init!(Self {
@@ -257,6 +254,8 @@ pub(crate) fn new<'bound>(
                     .inspect_err(|_| dev_err!(pdev, "GFW boot did not complete\n"))?;
             },
 
+            bar,
+
             sysmem_flush: SysmemFlush::register(pdev.as_ref(), bar, spec.chipset)?,
 
             gsp_falcon: Falcon::new(
@@ -270,19 +269,13 @@ pub(crate) fn new<'bound>(
             gsp <- Gsp::new(pdev),
 
             _: { gsp.boot(pdev, bar, spec.chipset, gsp_falcon, sec2_falcon)? },
-
-            bar: devres_bar,
         })
     }
 
     /// Called when the corresponding [`Device`](device::Device) is unbound.
     ///
     /// Note: This method must only be called from `Driver::unbind`.
-    pub(crate) fn unbind(&self, dev: &device::Device<device::Core>) {
-        kernel::warn_on!(self
-            .bar
-            .access(dev)
-            .inspect(|bar| self.sysmem_flush.unregister(bar))
-            .is_err());
+    pub(crate) fn unbind(&self) {
+        self.sysmem_flush.unregister(self.bar);
     }
 }
diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
index 49c093a0cb42..ed5eb39c8201 100644
--- a/drivers/gpu/nova-core/nova_core.rs
+++ b/drivers/gpu/nova-core/nova_core.rs
@@ -49,7 +49,7 @@ struct NovaCoreModule {
     // then `_debugfs_guard` clears `DEBUGFS_ROOT`.
     #[allow(clippy::type_complexity)]
     #[pin]
-    _driver: Registration<pci::Adapter<ForLt!(driver::NovaCore)>>,
+    _driver: Registration<pci::Adapter<ForLt!(driver::NovaCore<'_>)>>,
     _debugfs_guard: DebugfsRootGuard,
 }
 
-- 
2.54.0