From 8c349217994c2d2f188fe32ed014d26b497c8bf3 Mon Sep 17 00:00:00 2001
From: morgan <mc@m-labs.hk>
Date: Mon, 17 Jun 2024 13:19:37 +0800
Subject: [PATCH] cxp upconn gw: add low speed serial PHY

testing: add debug fifo output b4 encoder
cxp upconn: add low speed serial
cxp upconn: add reset, tx_busy, tx_enable
cxp upconn: add clockgen module for 20.83Mbps & 41.66Mbps using counters
cxp upconn: add oserdes using CEInserter
---
 src/gateware/cxp_upconn.py | 142 +++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 src/gateware/cxp_upconn.py

diff --git a/src/gateware/cxp_upconn.py b/src/gateware/cxp_upconn.py
new file mode 100644
index 0000000..dd7844c
--- /dev/null
+++ b/src/gateware/cxp_upconn.py
@@ -0,0 +1,142 @@
+from math import ceil
+
+from migen import *
+
+from misoc.cores.code_8b10b import SingleEncoder
+from misoc.interconnect import stream
+from misoc.interconnect.csr import *
+
+from cxp_pipeline import char_layout
+
+@ResetInserter()
+class ClockGen(Module):
+    def __init__(self, sys_clk_freq):
+        self.clk = Signal()
+        self.clk_10x = Signal() # 20.83MHz 48ns or 41.66MHz 24ns
+
+        self.freq2x_enable = Signal()
+        # # #
+
+        period = 1e9/sys_clk_freq
+        max_count = ceil(48/period)
+        counter = Signal(max=max_count, reset=max_count-1)
+
+        clk_div = Signal(max=10, reset=9)
+
+        self.sync += [
+            self.clk.eq(0),
+            self.clk_10x.eq(0),
+
+            If(counter == 0,
+                self.clk_10x.eq(1),
+                If(self.freq2x_enable,
+                    counter.eq(int(max_count/2)-1),
+                ).Else(
+                    counter.eq(counter.reset),
+                ),
+            ).Else(
+                counter.eq(counter-1),
+            ),
+
+            If(counter == 0,
+                If(clk_div == 0,
+                    self.clk.eq(1),
+                    clk_div.eq(clk_div.reset),
+                ).Else(
+                    clk_div.eq(clk_div-1),
+                )
+            )
+
+        ]
+
+@ResetInserter()
+@CEInserter()
+class SERDES_10bits(Module):
+    def __init__(self, pad):
+        self.oe = Signal()
+        self.d = Signal(10)
+
+        # # #
+
+        tx_bitcount = Signal(max=10)
+        tx_reg = Signal(10)
+
+        self.sync += [
+            If(self.oe,
+                # send LSB first
+                pad.eq(tx_reg[0]),
+                tx_reg.eq(Cat(tx_reg[1:], 0)),
+                tx_bitcount.eq(tx_bitcount + 1),   
+
+                If(tx_bitcount == 9,
+                    tx_bitcount.eq(0),
+                    tx_reg.eq(self.d),
+                ),
+            ).Else(
+                pad.eq(0),
+                tx_bitcount.eq(0),
+            )
+        ]
+
+class Transmitter(Module, AutoCSR):
+    def __init__(self, pad, sys_clk_freq):
+        self.bitrate2x_enable = Signal()
+        self.clk_reset = Signal()
+        self.enable = Signal()
+
+        # # #
+
+        self.sink = stream.Endpoint(char_layout)
+
+        self.submodules.cg = cg = ClockGen(sys_clk_freq)
+        self.submodules.encoder = encoder = SingleEncoder(True)
+
+        oe = Signal()
+        self.sync += [
+            If(self.enable,
+                self.sink.ack.eq(0),
+                If(cg.clk,
+                    oe.eq(1),
+                    encoder.disp_in.eq(encoder.disp_out),
+                    self.sink.ack.eq(1),
+                    encoder.d.eq(self.sink.data),
+                    encoder.k.eq(self.sink.k),
+                )
+            ).Else(
+                # discard packets until tx is enabled
+                self.sink.ack.eq(1),
+                oe.eq(0),
+            )
+        ]
+
+        self.submodules.serdes = serdes = SERDES_10bits(pad)
+
+        self.comb += [
+            cg.reset.eq(self.clk_reset),
+            cg.freq2x_enable.eq(self.bitrate2x_enable),
+
+            serdes.reset.eq(self.clk_reset),
+            serdes.ce.eq(cg.clk_10x),
+            serdes.d.eq(encoder.output),
+            serdes.oe.eq(oe),
+        ]
+
+class CXP_TXPHYs(Module, AutoCSR):
+    def __init__(self, pads, sys_clk_freq):
+        self.clk_reset = CSR()
+        self.bitrate2x_enable = CSRStorage()
+        self.enable = CSRStorage()
+
+        # # #
+
+
+        self.phys = []
+        for i, pad in enumerate(pads):
+            tx = Transmitter(pad, sys_clk_freq)
+            self.phys.append(tx)
+            setattr(self.submodules, "tx"+str(i), tx)
+            self.sync += [
+                tx.clk_reset.eq(self.clk_reset.re),
+                tx.bitrate2x_enable.eq(self.bitrate2x_enable.storage),
+                tx.enable.eq(self.enable.storage),
+            ]