[PATCH 4/4] gpu: nova-core: gsp: distinguish GMC events from responses in debug logs

[John Hubbard <jhubbard@nvidia.com>]

GSP-RM numbers its GMC events from bit 63 upward, apart from the
driver's request numbers, and marks a response with a flag in the
command word.

The GMC receive debug line printed the raw sequence and labeled every
element a receive:

    GSP GMC: receive: seq# 9223372036854775808, command=EXEC_GENERIC_BOOTLOADER (0x10002), length=0xb0
    GSP GMC: receive: seq# 0, command=GSP_INIT (0x10001), length=0x450

Print the sequence with bit 63 cleared, and label each received element
an event or a response by the flag:

    GSP GMC: event: seq# 0, command=EXEC_GENERIC_BOOTLOADER (0x10002), length=0xb0
    GSP GMC: response: seq# 0, command=GSP_INIT (0x10001), length=0x450

Assisted-by: LLM
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 35 +++++++++++++++++++++++--------
 drivers/gpu/nova-core/gsp/fw.rs   | 11 +++++++++-
 2 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index 2b53b1e6cebf..530ad51304ce 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -1062,10 +1062,17 @@ fn log_event(&self, function: Result<MsgFunction, u32>, seq: u32) {
     /// Logs a GMC message that no caller is waiting for: a response to a request that has already
     /// timed out, or an event that arrives outside the boot sequence.
     fn log_gmc_event(&self, header: &GspGmcMsgElement) {
+        let kind = if header.gmc.is_response() {
+            "response"
+        } else {
+            "event"
+        };
+
         dev_warn!(
             &self.dev,
-            "GSP GMC: dropping unclaimed message (seq {}, command={})\n",
-            header.gmc.sequence,
+            "GSP GMC: dropping unclaimed {} (seq# {}, command={})\n",
+            kind,
+            header.gmc.sequence_number(),
             GmcCommand(header.gmc.command_id()),
         );
     }
@@ -1268,13 +1275,23 @@ fn consume_element<R>(
                 message.header.function(),
                 message.header.length(),
             ),
-            QueueElement::Gmc(message) => dev_dbg!(
-                &self.dev,
-                "GSP GMC: receive: seq# {}, command={}, length=0x{:x}\n",
-                message.header.gmc.sequence,
-                GmcCommand(message.header.gmc.command_id()),
-                message.header.length(),
-            ),
+            QueueElement::Gmc(message) => {
+                let gmc = &message.header.gmc;
+                let kind = if gmc.is_response() {
+                    "response"
+                } else {
+                    "event"
+                };
+
+                dev_dbg!(
+                    &self.dev,
+                    "GSP GMC: {}: seq# {}, command={}, length=0x{:x}\n",
+                    kind,
+                    gmc.sequence_number(),
+                    GmcCommand(gmc.command_id()),
+                    message.header.length(),
+                )
+            }
         }
 
         let result = f(self, element);
diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index 106d71f95fc3..ec474a175ee6 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -729,6 +729,10 @@ pub(crate) struct GmcApiHeader {
 /// Flag bit of [`GmcApiHeader::command`] that GSP-RM sets on a response.
 const GMCAPI_COMMAND_FLAGS_RESPONSE: u32 = 0x0100_0000;
 
+/// First sequence number of the space that GSP-RM numbers its events from, so that an event's
+/// number cannot collide with a request's. Requests are numbered from zero.
+const GMC_EVENT_SEQUENCE_BASE: u64 = 1 << 63;
+
 /// GMC request that carries the system information and registry keys to GSP-RM. GSP-RM answers
 /// it with the static GPU configuration once it has finished starting.
 pub(crate) const GMCAPI_CMD_GSP_INIT: u32 = bindings::GMCAPI_COMMANDS_GMCAPI_CMD_GSP_INIT;
@@ -776,10 +780,15 @@ pub(crate) fn command_id(&self) -> u32 {
     }
 
     /// Returns `true` if GSP-RM sent this header as a response rather than an event.
-    fn is_response(&self) -> bool {
+    pub(crate) fn is_response(&self) -> bool {
         self.command & GMCAPI_COMMAND_FLAGS_RESPONSE != 0
     }
 
+    /// Returns the sequence number without the bit that marks an event's sequence space.
+    pub(crate) fn sequence_number(&self) -> u64 {
+        self.sequence & !GMC_EVENT_SEQUENCE_BASE
+    }
+
     /// Returns the `NV_STATUS` that a response carries.
     ///
     /// The value is meaningful only when [`Self::is_response`] is `true`. In a request, the same
-- 
2.55.0