Create read-only debugfs entries for LOGINIT, LOGRM, and LOGINTR, which
are the three primary printf logging buffers from GSP-RM.  LOGPMU will
be added at a later date, as it requires it support for its RPC message
first.

This patch uses the `pin_init_scope` feature to create the entries.
`pin_init_scope` solves the lifetime issue over the `DEBUGFS_ROOT`
reference by delaying its acquisition until the time the entry is
actually initialized.

Co-developed-by: Alexandre Courbot <[email protected]>
Signed-off-by: Alexandre Courbot <[email protected]>
Signed-off-by: Timur Tabi <[email protected]>
---
 drivers/gpu/nova-core/gsp.rs | 42 +++++++++++++++++++++++++++++-------
 1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp.rs b/drivers/gpu/nova-core/gsp.rs
index 860674dac31e..409ff80f55e6 100644
--- a/drivers/gpu/nova-core/gsp.rs
+++ b/drivers/gpu/nova-core/gsp.rs
@@ -3,6 +3,7 @@
 mod boot;
 
 use kernel::{
+    c_str,
     debugfs,
     device,
     dma::{
@@ -101,17 +102,24 @@ fn new(dev: &device::Device<device::Bound>) -> 
Result<Self> {
     }
 }
 
-/// GSP runtime data.
-#[pin_data]
-pub(crate) struct Gsp {
-    /// Libos arguments.
-    pub(crate) libos: CoherentAllocation<LibosMemoryRegionInitArgument>,
+/// Log buffers used by GSP-RM for debug logging.
+struct LogBuffers {
     /// Init log buffer.
     loginit: LogBuffer,
     /// Interrupts log buffer.
     logintr: LogBuffer,
     /// RM log buffer.
     logrm: LogBuffer,
+}
+
+/// GSP runtime data.
+#[pin_data]
+pub(crate) struct Gsp {
+    /// Libos arguments.
+    pub(crate) libos: CoherentAllocation<LibosMemoryRegionInitArgument>,
+    /// Log buffers, optionally exposed via debugfs.
+    #[pin]
+    logs: debugfs::Scope<LogBuffers>,
     /// Command queue.
     pub(crate) cmdq: Cmdq,
     /// RM arguments.
@@ -143,7 +151,9 @@ unsafe impl Sync for LogBuffer {}
 
 impl Gsp {
     // Creates an in-place initializer for a `Gsp` manager for `pdev`.
-    pub(crate) fn new(pdev: &pci::Device<device::Bound>) -> Result<impl 
PinInit<Self, Error>> {
+    pub(crate) fn new<'a>(
+        pdev: &'a pci::Device<device::Bound>,
+    ) -> Result<impl PinInit<Self, Error> + 'a> {
         let dev = pdev.as_ref();
         let libos = 
CoherentAllocation::<LibosMemoryRegionInitArgument>::alloc_coherent(
             dev,
@@ -173,11 +183,27 @@ pub(crate) fn new(pdev: &pci::Device<device::Bound>) -> 
Result<impl PinInit<Self
         dma_write!(rmargs[0] = fw::GspArgumentsCached::new(&cmdq))?;
         dma_write!(libos[3] = LibosMemoryRegionInitArgument::new("RMARGS", 
&rmargs))?;
 
-        Ok(try_pin_init!(Self {
-            libos,
+        let log_buffers = LogBuffers {
             loginit,
             logintr,
             logrm,
+        };
+
+        // Look up nova_core debugfs directory - only create entries if it 
exists.
+        // If nova_core doesn't exist, debugfs_dir will be empty and file 
creation
+        // becomes a no-op (data is still stored, just not exposed via 
debugfs).
+        let debugfs_dir = debugfs::Dir::lookup(c_str!("nova_core"), None)
+            .unwrap_or_else(debugfs::Dir::empty);
+
+        let logs = debugfs_dir.scope(log_buffers, pdev.name(), |logs, dir| {
+            dir.read_binary_file(c_str!("loginit"), &logs.loginit);
+            dir.read_binary_file(c_str!("logintr"), &logs.logintr);
+            dir.read_binary_file(c_str!("logrm"), &logs.logrm);
+        });
+
+        Ok(try_pin_init!(Self {
+            libos,
+            logs <- logs,
             rmargs,
             cmdq,
         }))
-- 
2.52.0

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