[PATCH v2 16/32] gpu: nova-core: gsp: wait for GMC completion events

[Zhi Wang <zhiw@nvidia.com>]

GSP plugin shutdown completes through a separate event carrying the
GFID. Releasing the queue lock between sending and waiting allows another
receiver to consume that completion.

Hold the lock until the caller's predicate matches the completion event.
Pass unmatched GMC events to the caller and keep one receive deadline
while processing interleaved traffic.

Co-developed-by: Alok Kumar <alkumar@nvidia.com>
Signed-off-by: Alok Kumar <alkumar@nvidia.com>
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 61 +++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index 891dec5c108a..137242ca0b11 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -745,6 +745,67 @@ pub(crate) fn send_gmc_and_check_status(&self, command_id: u32, payload: &[u8])
         }
     }
 
+    /// Sends an asynchronous GMC command and waits atomically for its event.
+    ///
+    /// The command queue remains locked from the send through the matching
+    /// event, preventing another transaction from consuming its completion.
+    /// Interleaved GMC events are passed to `handler`; responses are consumed
+    /// while waiting. The receive deadline starts after sending.
+    ///
+    /// Both callbacks run with the queue locked and must not reenter this queue or reset it.
+    /// Their second argument is the raw `max_resp_or_status` word of the event header.
+    #[expect(dead_code)]
+    pub(crate) fn send_gmc_and_wait_event(
+        &self,
+        command_id: u32,
+        payload: &[u8],
+        timeout: Delta,
+        mut predicate: impl FnMut(u32, u32, u64, &[u8], &[u8]) -> Result<bool>,
+        mut handler: impl FnMut(u32, u32, u64, &[u8], &[u8]) -> Result,
+    ) -> Result {
+        let mut inner = self.inner.lock();
+        inner.send_gmc(command_id, payload, 0)?;
+        let deadline = Instant::<Monotonic>::now() + timeout;
+
+        loop {
+            let remaining = deadline - Instant::<Monotonic>::now();
+            if remaining.is_negative() {
+                return Err(ETIMEDOUT);
+            }
+
+            let matched =
+                match inner.receive_gmc_and_dispatch(remaining, |header, payload_0, payload_1| {
+                    let header = &header.gmc;
+                    let result: Result<bool> = (|| {
+                        if header.is_response() {
+                            return Ok(false);
+                        }
+
+                        let command = header.command_id();
+                        let max_resp_or_status = header.max_resp_or_status;
+                        let sequence = header.sequence;
+                        if predicate(command, max_resp_or_status, sequence, payload_0, payload_1)? {
+                            return Ok(true);
+                        }
+
+                        handler(command, max_resp_or_status, sequence, payload_0, payload_1)?;
+                        Ok(false)
+                    })();
+                    (Some(result), QueuePointers::Unchanged)
+                }) {
+                    Ok(matched) => matched,
+                    Err(ERANGE) => continue,
+                    Err(error) => return Err(error),
+                };
+
+            if let Some(matched) = matched {
+                if matched? {
+                    return Ok(());
+                }
+            }
+        }
+    }
+
     /// Waits for an unsolicited GSP event of type `M`, consuming any other event that arrives
     /// first.
     ///