netboot: support 100Mbps and 10Mbps eth link speed

check for eth link change during netboot instead of defaulting to 1Gbps

szl/src/netboot.rs

@@ -6,7 +6,7 @@ use libboard_zynq::{devc,
                     eth::Eth,
                     smoltcp::{self,
                               iface::{EthernetInterfaceBuilder, NeighborCache},
-                              time::Instant,
+                              time::{Duration, Instant},
                               wire::IpCidr},
                     timer};
 use libconfig::{bootgen, net_settings};
@@ -335,6 +335,9 @@ pub fn netboot<File: Read + Seek>(bootgen_file: &mut Option<File>, runtime_start
     let mut boot_flag = false;
 
     log::info!("Waiting for connections...");
+
+    let mut last_link_check = Instant::from_millis(0);
+    const LINK_CHECK_INTERVAL: u64 = 500;
     loop {
         let timestamp = Instant::from_millis(timer::get_ms() as i64);
         {
@@ -375,5 +378,10 @@ pub fn netboot<File: Read + Seek>(bootgen_file: &mut Option<File>, runtime_start
             Err(smoltcp::Error::Unrecognized) => (),
             Err(err) => log::error!("Network error: {}", err),
         }
+        let dev = interface.device_mut();
+        if dev.is_idle() && timestamp >= last_link_check + Duration::from_millis(LINK_CHECK_INTERVAL) {
+            dev.check_link_change();
+            last_link_check = timestamp;
+        }
     }
 }