artiq_coreboot: block until hotswap image is actually received.

artiq/coredevice/comm_kernel.py

@@ -60,6 +60,8 @@ class _D2HMsgType(Enum):
     WATCHDOG_EXPIRED = 14
     CLOCK_FAILURE = 15
 
+    HOTSWAP_IMMINENT = 16
+
 
 class _LogLevel(Enum):
     OFF = 0
@@ -332,6 +334,8 @@ class CommKernel:
         self._write_header(_H2DMsgType.HOTSWAP)
         self._write_bytes(image)
 
+        self._read_empty(_D2HMsgType.HOTSWAP_IMMINENT)
+
     def load(self, kernel_library):
         self._write_header(_H2DMsgType.LOAD_KERNEL)
         self._write_bytes(kernel_library)

artiq/firmware/libproto/session_proto.rs

@@ -140,6 +140,8 @@ pub enum Reply<'a> {
 
     WatchdogExpired,
     ClockFailure,
+
+    HotswapImminent,
 }
 
 impl<'a> Reply<'a> {
@@ -219,6 +221,9 @@ impl<'a> Reply<'a> {
             Reply::ClockFailure => {
                 writer.write_u8(15)?;
             },
+            Reply::HotswapImminent => {
+                writer.write_u8(16)?;
+            }
         }
         Ok(())
     }

artiq/firmware/runtime/session.rs

@@ -116,6 +116,7 @@ fn host_read(stream: &mut TcpStream) -> io::Result<host::Request> {
     let request = host::Request::read_from(stream)?;
     match &request {
         &host::Request::LoadKernel(_) => debug!("comm<-host LoadLibrary(...)"),
+        &host::Request::Hotswap(_) => debug!("comm<-host Hotswap(...)"),
         _ => debug!("comm<-host {:?}", request)
     }
     Ok(request)
@@ -269,8 +270,12 @@ fn process_host_message(io: &Io,
         }
 
         // artiq_coreboot
-        host::Request::Hotswap(binary) =>
-            unsafe { board::hotswap::run(&binary) },
+        host::Request::Hotswap(binary) => {
+            host_write(stream, host::Reply::HotswapImminent)?;
+            stream.close()?;
+            warn!("hotswapping firmware");
+            unsafe { board::hotswap::run(&binary) }
+        }
 
         // artiq_run/artiq_master
         host::Request::SwitchClock(clk) => {