From 7edc491f6fca8e22f51e37a16d74914cd959274d Mon Sep 17 00:00:00 2001
From: Alistair Popple <apopple@nvidia.com>
Date: Wed, 9 Sep 2026 16:45:02 +1000
Subject: [PATCH] drm: nova: Use nova-core to read VRAM_BAR_SIZE parameter

Currently nova-drm reads the VRAM BAR size directly from the PCIe device
which requires trying to cast the parent device into a PCIe device. This
obviously requires the parent device to actually be a PCIe bus device.
Whilst that is true today it may not always be the case, and there
is no reason to make this assumption now that NovaCoreApi can hold a
reference to the bound PCIe device.

So convert nova-drm to using nova-core to obtain the VRAM_BAR_SIZE
parameter.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Link: https://patch.msgid.link/20260909064506.910162-10-apopple@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 drivers/gpu/drm/nova/file.rs    | 12 +++---------
 drivers/gpu/nova-core/api.rs    |  8 ++++++++
 drivers/gpu/nova-core/driver.rs |  2 +-
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/nova/file.rs b/drivers/gpu/drm/nova/file.rs
index 988f639af116..38aca1a1e3a4 100644
--- a/drivers/gpu/drm/nova/file.rs
+++ b/drivers/gpu/drm/nova/file.rs
@@ -8,8 +8,6 @@
 use crate::gem::NovaObject;
 use kernel::{
     alloc::flags::*,
-    auxiliary,
-    device::Bound,
     drm::{
         self,
         gem::BaseObject,
@@ -19,7 +17,6 @@
         arch::IntoSafeCastArch,
         IntoSafeCast, //
     },
-    pci,
     prelude::*,
     transmute::AsBytes,
     uaccess::UserSlice,
@@ -85,16 +82,13 @@ fn open(_dev: &NovaDevice) -> Result<Pin<KBox<Self>>> {
 impl File {
     /// IOCTL: get_param: Query GPU / driver metadata.
     pub(crate) fn get_param(
-        dev: &NovaDevice<Registered>,
-        _reg_data: &DrmRegData<'_>,
+        _dev: &NovaDevice<Registered>,
+        reg_data: &DrmRegData<'_>,
         getparam: &mut uapi::drm_nova_getparam,
         _file: &drm::File<File>,
     ) -> Result<u32> {
-        let adev: &auxiliary::Device<Bound> = dev.as_ref();
-        let pdev: &pci::Device<Bound> = adev.parent().try_into()?;
-
         let value = match getparam.param.try_into()? {
-            uapi::NOVA_GETPARAM_VRAM_BAR_SIZE => pdev.resource_len(1)?,
+            uapi::NOVA_GETPARAM_VRAM_BAR_SIZE => reg_data.api.with(|api| api.bar1_size())?,
             _ => return Err(EINVAL),
         };
 
diff --git a/drivers/gpu/nova-core/api.rs b/drivers/gpu/nova-core/api.rs
index 64f9ea442278..f02c6c7c7e51 100644
--- a/drivers/gpu/nova-core/api.rs
+++ b/drivers/gpu/nova-core/api.rs
@@ -8,6 +8,7 @@
 use kernel::{
     auxiliary,
     device::Bound,
+    pci,
     prelude::*,
     types::ForLt, //
 };
@@ -20,6 +21,7 @@
 /// API handle for the auxiliary bus child drivers to interact with nova-core.
 pub struct NovaCoreApi<'bound> {
     pub(crate) gpu: Pin<&'bound Gpu<'bound>>,
+    pub(crate) pdev: &'bound pci::Device<Bound>,
 }
 
 impl NovaCoreApi<'_> {
@@ -38,6 +40,12 @@ pub fn gsp_static_info(&self) -> &GetGspStaticInfoReply {
     pub fn spec(&self) -> &Spec {
         &self.gpu.spec
     }
+
+    /// Returns the size of the PCIe BAR used for accessing VRAM, typically
+    /// BAR1.
+    pub fn bar1_size(&self) -> Result<u64> {
+        self.pdev.resource_len(1)
+    }
 }
 
 /// Expose a handle to nova-core API
diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
index d2f20943142d..bdaed5408a00 100644
--- a/drivers/gpu/nova-core/driver.rs
+++ b/drivers/gpu/nova-core/driver.rs
@@ -146,7 +146,7 @@ fn probe<'bound>(
                             // never recycles IDs.
                             AUXILIARY_ID_COUNTER.fetch_add(1, Relaxed),
                             crate::MODULE_NAME,
-                            NovaCoreApi { gpu },
+                            NovaCoreApi { gpu, pdev },
                         )?
                     }
                 },