stm32/spi: more exhaustive test.

tests/stm32/src/bin/spi_dma.rs

@@ -50,6 +50,18 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     spi.transfer_in_place(&mut buf).await.unwrap();
     assert_eq!(buf, data);
 
+    // Check read/write don't hang. We can't check they transfer the right data
+    // without fancier test mechanisms.
+    spi.write(&buf).await.unwrap();
+    spi.read(&mut buf).await.unwrap();
+    spi.write(&buf).await.unwrap();
+    spi.read(&mut buf).await.unwrap();
+    spi.write(&buf).await.unwrap();
+
+    // Check transfer doesn't break after having done a write, due to garbage in the FIFO
+    spi.transfer(&mut buf, &data).await.unwrap();
+    assert_eq!(buf, data);
+
     info!("Test OK");
     cortex_m::asm::bkpt();
 }