[PATCH v4 09/17] gpu: nova-core: log GSP events instead of discarding them

[John Hubbard]

The GSP posts unsolicited messages on the same queue that carries
command replies: log records, OS error and robust-channel records, and
lifecycle notices.

nova-core discarded every message that was not the reply a caller was
waiting for, and an unrecognized function code aborted the in-flight
command. The GSP's error reports never reached the kernel log.

Log every non-reply message according to its function code, on the
receive path that already reads it, and leave the in-flight command
waiting for its reply. Event payloads, such as XID numbers and log
contents, are not decoded.

Assisted-by: LLM
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 52 ++++++++++++++++++++++++-------
 1 file changed, 41 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index 9f99e6bbb4fa..340760e384d0 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -557,8 +557,7 @@ fn notify_gsp(bar: Bar0<'_>) {
 
     /// Sends `command` to the GSP and waits for the reply.
     ///
-    /// Messages with non-matching function codes are silently consumed until the expected reply
-    /// arrives.
+    /// Events that arrive before the reply are logged and consumed.
     ///
     /// The queue is locked for the entire send+receive cycle to ensure that no other command can
     /// be interleaved.
@@ -815,8 +814,8 @@ fn wait_for_msg(&self, timeout: Delta) -> Result<GspMessage<'_>> {
 
     /// Receive a message from the GSP.
     ///
-    /// The expected message type is specified using the `M` generic parameter. If the pending
-    /// message has a different function code, `ERANGE` is returned and the message is consumed.
+    /// A message whose function code is `M::FUNCTION` is decoded and returned. Any other message
+    /// is logged as an event.
     ///
     /// The read pointer is always advanced past the message, regardless of whether it matched.
     ///
@@ -825,8 +824,7 @@ fn wait_for_msg(&self, timeout: Delta) -> Result<GspMessage<'_>> {
     /// - `ETIMEDOUT` if `timeout` has elapsed before any message becomes available.
     /// - `EIO` if there was some inconsistency (e.g. message shorter than advertised) on the
     ///   message queue.
-    /// - `EINVAL` if the function code of the message was not recognized.
-    /// - `ERANGE` if the message had a recognized but non-matching function code.
+    /// - `ERANGE` if the message was not the awaited reply.
     ///
     /// Error codes returned by [`MessageFromGsp::read`] are propagated as-is.
     fn receive_msg<M: MessageFromGsp>(&mut self, timeout: Delta) -> Result<M>
@@ -835,11 +833,11 @@ fn receive_msg<M: MessageFromGsp>(&mut self, timeout: Delta) -> Result<M>
         Error: From<M::InitError>,
     {
         let message = self.wait_for_msg(timeout)?;
-        let function = message.header.function().map_err(|_| EINVAL)?;
+        let function = message.header.function();
+        let seq = message.header.sequence();
 
-        // Extract the message. Store the result as we want to advance the read pointer even in
-        // case of failure.
-        let result = if function == M::FUNCTION {
+        // An early return here would leave the read pointer on this message.
+        let result = if matches!(function, Ok(f) if f == M::FUNCTION) {
             let (cmd, contents_1) = M::Message::from_bytes_prefix(message.contents.0).ok_or(EIO)?;
             let mut sbuffer = SBufferIter::new_reader([contents_1, message.contents.1]);
 
@@ -850,11 +848,13 @@ fn receive_msg<M: MessageFromGsp>(&mut self, timeout: Delta) -> Result<M>
                         dev_warn!(
                             &self.dev,
                             "GSP message {:?} has unprocessed data\n",
-                            function
+                            M::FUNCTION
                         );
                     }
                 })
         } else {
+            self.log_event(function, seq);
+
             Err(ERANGE)
         };
 
@@ -865,4 +865,34 @@ fn receive_msg<M: MessageFromGsp>(&mut self, timeout: Delta) -> Result<M>
 
         result
     }
+
+    /// Logs an event, meaning a message that no caller was waiting for.
+    ///
+    /// An OS error or robust-channel record is logged at error level and an unknown function code
+    /// at warning level. Every other event is recorded only by the receive trace in
+    /// [`Self::wait_for_msg`].
+    fn log_event(&self, function: Result<MsgFunction, u32>, seq: u32) {
+        match function {
+            Ok(MsgFunction::OsErrorLog) => {
+                dev_err!(&self.dev, "GSP reported an OS error (seq {})\n", seq);
+            }
+            Ok(MsgFunction::RcTriggered) => {
+                dev_err!(
+                    &self.dev,
+                    "GSP triggered robust-channel recovery (seq {})\n",
+                    seq
+                );
+            }
+            // Nothing to do for the remaining known function codes.
+            Ok(_) => {}
+            Err(raw) => {
+                dev_warn!(
+                    &self.dev,
+                    "unknown GSP message function {:#x} (seq {})\n",
+                    raw,
+                    seq
+                );
+            }
+        }
+    }
 }
-- 
2.55.0