[PATCH v2 04/31] gpu: nova-core: set MCTP transport header version to 1

[John Hubbard]

FSP requires MCTP transport header version 1. Nova-core leaves version
bits 3:0 at zero, so every CoT and PRC request carries an invalid
transport header.

Define the version and destination endpoint ID fields. Set the version
to 1 for single-packet requests, and leave the unused destination
endpoint ID at zero.

Assisted-by: Cursor:claude-opus-5
Reviewed-by: Timur Tabi <ttabi@xxxxxxxxxx>
Reviewed-by: Zhi Wang <zhiw@xxxxxxxxxx>
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 Documentation/gpu/nova/core/fsp.rst |  2 ++
 drivers/gpu/nova-core/mctp.rs       | 14 ++++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/Documentation/gpu/nova/core/fsp.rst b/Documentation/gpu/nova/core/fsp.rst
index 52d618d22bb8..60c647181da0 100644
--- a/Documentation/gpu/nova/core/fsp.rst
+++ b/Documentation/gpu/nova/core/fsp.rst
@@ -106,6 +106,8 @@ All FSP messages share a common header format consisting of two 32-bit words:
 - Bit 30: EOM (End of Message)
 - Bits 29:28: Packet sequence number
 - Bits 23:16: Source Endpoint ID
+- Bits 15:8: Destination Endpoint ID
+- Bits 3:0: MCTP header version (1)
 
 **NVDM header** (NVIDIA Vendor Defined Message):
 
diff --git a/drivers/gpu/nova-core/mctp.rs b/drivers/gpu/nova-core/mctp.rs
index 90c642c91a72..03546213da28 100644
--- a/drivers/gpu/nova-core/mctp.rs
+++ b/drivers/gpu/nova-core/mctp.rs
@@ -42,13 +42,23 @@ pub(crate) struct MctpHeader(u32) {
         29:28 seq;
         /// Source endpoint ID.
         23:16 seid;
+        /// Destination endpoint ID.
+        15:8 deid;
+        /// MCTP header version.
+        3:0 version;
     }
 }
 
 impl MctpHeader {
-    /// Builds a single-packet MCTP header (`SOM=1`, `EOM=1`, `SEQ=0`, `SEID=0`).
+    /// MCTP specification version 1.0.
+    const VERSION: u32 = 1;
+
+    /// Builds a single-packet MCTP header (`SOM=1`, `EOM=1`, `SEQ=0`, `SEID=0`, `VERSION=1`).
     pub(crate) fn single_packet() -> Self {
-        Self::zeroed().with_som(true).with_eom(true)
+        Self::zeroed()
+            .with_const_version::<{ Self::VERSION }>()
+            .with_som(true)
+            .with_eom(true)
     }
 
     /// Returns whether this is a complete single-packet message (`SOM=1` and `EOM=1`).
-- 
2.55.0