[PATCH v2 31/31] gpu: nova-core: distinguish GMC event and response debug logs

[John Hubbard <jhubbard@nvidia.com>]

GSP-initiated GMC events assign sequence numbers starting at bit 63 so
they cannot collide with driver request sequences, which start at zero.

The receive debug line printed the raw 64-bit value, so the first boot
event showed seq# 9223372036854775808 (0x8000000000000000), and it
labeled the GSP_INIT reply as an event.

Print the sequence with that bit cleared, and label a reply as a
response. Sample output on a Turing GPU:

nova-core 0000:c1:00.0: GSP GMC: send: seq# 0, command=GSP_INIT (0x10001), length=0xf8
nova-core 0000:c1:00.0: GSP GMC: event: seq# 0, command=EXEC_GENERIC_BOOTLOADER (0x10002), length=0xb0
nova-core 0000:c1:00.0: GSP GMC: response: seq# 0, command=GSP_INIT (0x10001), length=0x450

Assisted-by: Cursor:grok-4.6
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 10 ++++++++--
 drivers/gpu/nova-core/gsp/fw.rs   | 17 +++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index 8e97cc71f2b6..e6931f65b167 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -1299,11 +1299,17 @@ fn receive_gmc_and_dispatch<R>(
             (None, QueuePointers::Unchanged)
         } else {
             let command_id = header.gmc.command_id();
+            let kind = if header.gmc.is_response() {
+                "response"
+            } else {
+                "event"
+            };
 
             dev_dbg!(
                 &self.dev,
-                "GSP GMC: event: seq# {}, command={}, length=0x{:x}\n",
-                header.gmc.sequence,
+                "GSP GMC: {}: seq# {}, command={}, length=0x{:x}\n",
+                kind,
+                header.gmc.sequence_number(),
                 GmcCommand(command_id),
                 length,
             );
diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index 927332203a43..150c8042867a 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -674,6 +674,13 @@ pub(crate) struct GmcApiHeader {
 /// `GMCAPI_HEADER_COMMAND_ID_MASK`. The remaining byte carries flags.
 const GMCAPI_COMMAND_ID_MASK: u32 = 0x00ff_ffff;
 
+/// Response flag in the high byte of [`GmcApiHeader::command`].
+const GMCAPI_COMMAND_FLAGS_RESPONSE: u32 = 0x0100_0000;
+
+/// GSP-initiated events set [`GmcApiHeader::sequence`] starting at this value so they
+/// cannot collide with driver request sequences, which start at zero.
+const GMC_EVENT_SEQUENCE_BASE: u64 = 1 << 63;
+
 /// GMC command that hands GSP-RM its system information and registry keys and returns the static
 /// GPU configuration. Its reply is also what signals that GSP-RM has finished starting.
 pub(crate) const GMCAPI_CMD_GSP_INIT: u32 = bindings::GMCAPI_COMMANDS_GMCAPI_CMD_GSP_INIT;
@@ -715,6 +722,16 @@ impl GmcApiHeader {
     pub(crate) fn command_id(&self) -> u32 {
         self.command & GMCAPI_COMMAND_ID_MASK
     }
+
+    /// Returns `true` if this header is a reply to a driver request.
+    pub(crate) fn is_response(&self) -> bool {
+        self.command & GMCAPI_COMMAND_FLAGS_RESPONSE != 0
+    }
+
+    /// Returns [`Self::sequence`] with the GSP-initiated-event bit cleared.
+    pub(crate) fn sequence_number(&self) -> u64 {
+        self.sequence & !GMC_EVENT_SEQUENCE_BASE
+    }
 }
 
 // SAFETY: All fields are integer types with no uninitialized padding bytes.
-- 
2.55.0