[PATCH 1/3] gpu: nova-core: fsp: wait to consume message before sending another

[Eliot Courtney <ecourtney@nvidia.com>]

FSP can only get one message at a time, so make sure it has consumed the
previous one before trying to give it another.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/falcon/fsp.rs | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/falcon/fsp.rs b/drivers/gpu/nova-core/falcon/fsp.rs
index f618a681ff28..1497f163806e 100644
--- a/drivers/gpu/nova-core/falcon/fsp.rs
+++ b/drivers/gpu/nova-core/falcon/fsp.rs
@@ -7,12 +7,14 @@
 
 use kernel::{
     io::{
+        poll::read_poll_timeout,
         register::WithBase,
         Io,
         IoCapable, //
     },
     num::Bounded,
-    prelude::*, //
+    prelude::*,
+    time::Delta, //
 };
 
 use kernel::io::register::RegisterBase;
@@ -186,6 +188,18 @@ pub(crate) fn send_msg(&self, bar: &Bar0, packet: &[u8]) -> Result {
             return Err(EINVAL);
         }
 
+        // Wait for FSP to consume any previous message before sending.
+        read_poll_timeout(
+            || {
+                let head = bar.read(regs::NV_PFSP_QUEUE_HEAD).address().get();
+                let tail = bar.read(regs::NV_PFSP_QUEUE_TAIL).address().get();
+                Ok(head == tail)
+            },
+            |&ready| ready,
+            Delta::from_millis(1),
+            Delta::from_secs(2),
+        )?;
+
         // Write message to EMEM at offset 0 (validates 4-byte alignment)
         self.write_emem(bar, 0, packet)?;
 

-- 
2.53.0