From 865434763dac1f0795022e0295da2b4e510d6e8f Mon Sep 17 00:00:00 2001
From: morgan <mc@m-labs.hk>
Date: Fri, 26 Jul 2024 16:24:18 +0800
Subject: [PATCH] cxp downconn: fix bruteforcealigner

---
 src/gateware/cxp_downconn.py | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/gateware/cxp_downconn.py b/src/gateware/cxp_downconn.py
index 588bf64..5226f36 100644
--- a/src/gateware/cxp_downconn.py
+++ b/src/gateware/cxp_downconn.py
@@ -8,7 +8,6 @@ from misoc.interconnect.csr import *
 from artiq.gateware.drtio.transceiver.gtx_7series_init import *
 
 from operator import add
-from math import ceil
 from functools import reduce
 
 # Changes the phase of the transceiver RX clock to align the comma to
@@ -28,17 +27,16 @@ from functools import reduce
 # Warning: Xilinx transceivers are LSB first, and comma needs to be flipped
 # compared to the usual 8b10b binary representation.
 class CXP_BruteforceClockAligner(Module):
-    def __init__(self, comma, sys_clk_freq, check_period):
+    def __init__(self, comma, check_max_val):
         self.rxdata = Signal(20)
         self.restart = Signal()
 
         self.ready = Signal()
 
-        check_max_val = ceil(check_period*sys_clk_freq)
         check_counter = Signal(max=check_max_val+1)
         check = Signal()
         reset_check_counter = Signal()
-        self.sync += [
+        self.sync.cxp_gtx_tx += [
             check.eq(0),
             If(reset_check_counter,
                 check_counter.eq(check_max_val)
@@ -52,7 +50,7 @@ class CXP_BruteforceClockAligner(Module):
             )
         ]
 
-        checks_reset = PulseSynchronizer("sys", "cxp_gtx_rx")
+        checks_reset = PulseSynchronizer("cxp_gtx_tx", "cxp_gtx_rx")
         self.submodules += checks_reset
 
         comma_n = ~comma & 0b1111111111
@@ -81,7 +79,7 @@ class CXP_BruteforceClockAligner(Module):
             )
         ]
 
-        fsm = FSM(reset_state="WAIT_COMMA")
+        fsm = ClockDomainsRenamer("cxp_gtx_tx")(FSM(reset_state="WAIT_COMMA"))
         self.submodules += fsm
 
         fsm.act("WAIT_COMMA",
@@ -130,7 +128,7 @@ class CXP_DownConn(Module):
         assert tx_mode in ["single", "master", "slave"]
         assert rx_mode in ["single", "master", "slave"]
 
-        cpll_div = 5
+        cpll_div = 4
         cpll_div45 = 5
         refclk_div = 1
         Xxout_div = 2
@@ -162,7 +160,7 @@ class CXP_DownConn(Module):
         # TX generates cxp_tx clock, init must be in system domain
         self.submodules.tx_init = tx_init = GTXInit(sys_clk_freq, False, mode=tx_mode)
         # RX receives restart commands from RTIO domain
-        self.submodules.rx_init = rx_init = GTXInit(sys_clk_freq, True, mode=rx_mode)
+        self.submodules.rx_init = rx_init = ClockDomainsRenamer("cxp_gtx_tx")(GTXInit(sys_clk_freq, True, mode=rx_mode))
         self.comb += [
             cpllreset.eq(tx_init.cpllreset),
             tx_init.cplllock.eq(cplllock),
@@ -422,8 +420,11 @@ class CXP_DownConn(Module):
             self.decoders[1].input.eq(rxdata[10:])
         ]
 
-        # 6e-3 is too slow for 3.25Gbps line rate
-        clock_aligner = CXP_BruteforceClockAligner(0b0101111100, sys_clk_freq, check_period=1e-2)
+        # 62.5MHz: cannot align
+        # 125MHz: align <1s
+        # 156.25MHz: align <15s
+        # 250MHz: cannot align
+        clock_aligner = CXP_BruteforceClockAligner(0b0101111100, 1_000_000)
         self.submodules += clock_aligner
         self.comb += [
             clock_aligner.rxdata.eq(rxdata),