From 0c32d07e8b59e60ee304753e732bfa0c07e0daa6 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Wed, 20 Jun 2018 00:15:58 +0800
Subject: [PATCH] ad9154: new sysref scan

Print margins around the pre-defined fixed phase.
Also report error if margins are too small.

The fixed phase is also changed by this commit (the value 88 is
from before the new HMC7043 initialization code, and is probably wrong).
---
 artiq/firmware/libboard_artiq/ad9154.rs | 75 ++++++++++++++++---------
 1 file changed, 49 insertions(+), 26 deletions(-)

diff --git a/artiq/firmware/libboard_artiq/ad9154.rs b/artiq/firmware/libboard_artiq/ad9154.rs
index 34a9cbe34..65a130311 100644
--- a/artiq/firmware/libboard_artiq/ad9154.rs
+++ b/artiq/firmware/libboard_artiq/ad9154.rs
@@ -689,36 +689,58 @@ fn dac_cfg_retry(dacno: u8) -> Result<(), &'static str> {
     }
 }
 
-fn dac_sysref_scan(dacno: u8) {
-    let mut sync_error_last = 0;
-    let mut phase_min = None;
-    let mut phase_max = None;
+fn dac_get_sync_error(dacno: u8) -> u16 {
+    spi_setup(dacno);
+    let sync_error = ((read(ad9154_reg::SYNC_CURRERR_L) as u16) |
+                     ((read(ad9154_reg::SYNC_CURRERR_H) as u16) << 8))
+                     & 0x1ff;
+    sync_error
+}
 
-    info!("AD9154-{} SYSREF scan:", dacno);
-    for phase in 0..512 {
-        hmc7043::cfg_dac_sysref(dacno, phase);
+fn dac_sysref_scan(dacno: u8, center_phase: u16) {
+    let mut margin_minus = None;
+    let mut margin_plus = None;
+
+    info!("AD9154-{} SYSREF scan...", dacno);
+
+    hmc7043::cfg_dac_sysref(dacno, center_phase);
+    clock::spin_us(10000);
+    let mut sync_error_last = dac_get_sync_error(dacno);
+    for d in 0..128 {
+        hmc7043::cfg_dac_sysref(dacno, center_phase - d);
         clock::spin_us(10000);
-        spi_setup(dacno);
-        let sync_error = ((read(ad9154_reg::SYNC_CURRERR_L) as u16) |
-                         ((read(ad9154_reg::SYNC_CURRERR_H) as u16) << 8))
-                         & 0x1ff;
+        let sync_error = dac_get_sync_error(dacno);
         if sync_error != sync_error_last {
-            info!("  phase: {}, sync error: {}", phase, sync_error);
+            info!("  sync error-: {} -> {}", sync_error_last, sync_error);
+            margin_minus = Some(d);
+            break;
         }
-        if sync_error != 0 {
-            if phase_min.is_some() {
-                if sync_error != sync_error_last {
-                    phase_max = Some(phase - 1);
-                    break;
-                }
-            } else {
-                phase_min = Some(phase);
-            }
-        }
-        sync_error_last = sync_error;
     }
 
-    info!("  phase min: {:?}, phase max: {:?}", phase_min, phase_max);
+    hmc7043::cfg_dac_sysref(dacno, center_phase);
+    clock::spin_us(10000);
+    sync_error_last = dac_get_sync_error(dacno);
+    for d in 0..128 {
+        hmc7043::cfg_dac_sysref(dacno, center_phase + d);
+        clock::spin_us(10000);
+        let sync_error = dac_get_sync_error(dacno);
+        if sync_error != sync_error_last {
+            info!("  sync error+: {} -> {}", sync_error_last, sync_error);
+            margin_plus = Some(d);
+            break;
+        }
+    }
+
+    if margin_minus.is_some() && margin_plus.is_some() {
+        let margin_minus = margin_minus.unwrap();
+        let margin_plus = margin_plus.unwrap();
+        info!("  margins: -{} +{}", margin_minus, margin_plus);
+        if margin_minus < 10 || margin_plus < 10 {
+            error!("SYSREF margins are too small");
+        }
+    } else {
+        error!("Unable to determine SYSREF margins");
+    }
 }
 
 fn dac_sysref_cfg(dacno: u8, phase: u16) {
@@ -735,9 +757,10 @@ fn init_dac(dacno: u8) -> Result<(), &'static str> {
     // Run the PRBS, STPL and SYSREF scan tests
     dac_prbs(dacno)?;
     dac_stpl(dacno, 4, 2)?;
-    dac_sysref_scan(dacno);
+    let sysref_phase = 58;
+    dac_sysref_scan(dacno, sysref_phase);
     // Set SYSREF phase and reconfigure the DAC
-    dac_sysref_cfg(dacno, 88);
+    dac_sysref_cfg(dacno, sysref_phase);
     dac_cfg_retry(dacno)?;
     Ok(())
 }