firmware: make DAC initialization failures non-fatal

This allows using RTMs with one broken DAC for development.

artiq/firmware/libboard_artiq/ad9154.rs

@@ -720,12 +720,7 @@ fn dac_sysref_cfg(dacno: u8, phase: u16) {
     hmc7043::cfg_dac_sysref(dacno, phase);
 }
 
-pub fn init() -> Result<(), &'static str> {
+fn init_dac(dacno: u8) -> Result<(), &'static str> {
-    // Release the JESD clock domain reset late, as we need to
-    // set up clock chips before.
-    jesd_unreset();
-
-    for dacno in 0..csr::AD9154.len() {
     let dacno = dacno as u8;
     // Reset the DAC, detect and configure it
     dac_reset(dacno);
@@ -738,7 +733,18 @@ pub fn init() -> Result<(), &'static str> {
     // Set SYSREF phase and reconfigure the DAC
     dac_sysref_cfg(dacno, 88);
     dac_cfg_retry(dacno)?;
-    }
-
     Ok(())
 }
+
+pub fn init() {
+    // Release the JESD clock domain reset late, as we need to
+    // set up clock chips before.
+    jesd_unreset();
+
+    for dacno in 0..csr::AD9154.len() {
+        match init_dac(dacno as u8) {
+            Ok(_) => (),
+            Err(e) => error!("failed to initialize AD9154-{}: {}", dacno, e)
+        }
+    }
+}

artiq/firmware/runtime/main.rs

@@ -109,7 +109,7 @@ fn startup() {
     /* must be the first SPI init because of HMC830 SPI mode selection */
     board_artiq::hmc830_7043::init().expect("cannot initialize HMC830/7043");
     #[cfg(has_ad9154)]
-    board_artiq::ad9154::init().expect("cannot initialize AD9154");
+    board_artiq::ad9154::init();
     #[cfg(has_allaki_atts)]
     board_artiq::hmc542::program_all(8/*=4dB*/);