From e74d7f989871e968b5ab31d6f50c7e2b2bc787b5 Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Tue, 14 Apr 2020 18:25:33 +0100
Subject: [PATCH] add fu-fu multi-rd/wr dep cell

---
 src/soc/scoreboard/fu_dep_cell_multi.py | 125 ++++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 src/soc/scoreboard/fu_dep_cell_multi.py

diff --git a/src/soc/scoreboard/fu_dep_cell_multi.py b/src/soc/scoreboard/fu_dep_cell_multi.py
new file mode 100644
index 00000000..4643f3c2
--- /dev/null
+++ b/src/soc/scoreboard/fu_dep_cell_multi.py
@@ -0,0 +1,125 @@
+from nmigen.compat.sim import run_simulation
+from nmigen.cli import verilog, rtlil
+from nmigen import Module, Signal, Const, Elaboratable, Array
+from nmutil.latch import SRLatch
+
+from functools import reduce
+from operator import or_
+
+
+class FUDependenceCell(Elaboratable):
+    """ implements 11.4.7 mitch alsup dependence cell, p27
+    """
+    def __init__(self, dummy, n_fu, n_src, n_dest):
+        self.n_fu = n_fu
+        self.n_src = n_src
+        self.n_dest = n_dest
+        self.dummy = Const(~(1<<dummy), n_fu)
+        # inputs
+        self.rd_pend_i = Signal(n_fu, reset_less=True) # read pend in (left)
+        self.wr_pend_i = Signal(n_fu, reset_less=True) # write pend in (left)
+        self.issue_i = Signal(n_fu, reset_less=True)    # Issue in (top)
+
+        # set up go_wr and go_wr array
+        rd = []
+        for i in range(n_src):
+            j = i + 1 # name numbering to match src1/src2
+            rd.append(Signal(n_fu, name="gord%d_i" % j, reset_less=True))
+        wr = []
+        for i in range(n_src):
+            j = i + 1 # name numbering to match src1/src2
+            wr.append(Signal(n_fu, name="gowr%d_i" % j, reset_less=True))
+
+        self.go_wr_i = Array(wr)  # Go Write in (left)
+        self.go_rd_i = Array(rd)  # Go Read in (left)
+
+        self.go_die_i = Signal(n_fu, reset_less=True) # Go Die in (left)
+
+        # outputs (latched rd/wr wait)
+        self.rd_wait_o = Signal(n_fu, reset_less=True) # read wait out (right)
+        self.wr_wait_o = Signal(n_fu, reset_less=True) # write wait out (right)
+
+    def elaborate(self, platform):
+        m = Module()
+
+        # set up rd/wr latches
+        rd_c = []
+        for i in range(self.n_src):
+            rd_l = SRLatch(sync=False, name="rd%d_c" % i, llen=self.n_fu)
+            setattr(m.submodules, "src%d_c" % (i+1), rd_l)
+            rd_c.append(rd_l)
+        wr_c = []
+        for i in range(self.n_dest):
+            wr_l = SRLatch(sync=False, name="wr%d_c" % i, llen=self.n_fu)
+            setattr(m.submodules, "dst%d_c" % (i+1), wr_l)
+            wr_c.append(wr_l)
+
+        # reset on go HI, set on dest and issue
+
+        # connect go_wr / pend
+        for i in range(self.n_dest):
+            m.d.comb += wr_c[i].r.eq(self.go_wr_i[i] | self.go_die_i)
+            m.d.comb += wr_c[i].s.eq(self.issue_i & self.wr_pend_i & self.dummy)
+
+        # connect go_rd / pend_i
+        for i in range(self.n_src):
+            m.d.comb += rd_c[i].r.eq(self.go_rd_i[i] | self.go_die_i)
+            m.d.comb += rd_c[i].s.eq(self.issue_i & self.rd_pend_i & self.dummy)
+
+        # connect output with OR-reduce (DO NOT USE bool()!)
+        # read-wait (and write-wait) only go off when all GORD (and GOWR) fire
+        rd_q = []
+        for i in range(self.n_src):
+            rd_q.append(rd_c[i].qlq)
+        m.d.comb += self.rd_wait_o.eq(reduce(or_, rd_q) & ~self.issue_i)
+        wr_q = []
+        for i in range(self.n_dest):
+            wr_q.append(wr_c[i].qlq)
+        m.d.comb += self.wr_wait_o.eq(reduce(or_, wr_q) & ~self.issue_i)
+
+        return m
+
+    def __iter__(self):
+        yield self.rd_pend_i
+        yield self.wr_pend_i
+        yield self.issue_i
+        yield from self.go_wr_i
+        yield from self.go_rd_i
+        yield self.go_die_i
+        yield self.rd_wait_o
+        yield self.wr_wait_o
+                
+    def ports(self):
+        return list(self)
+
+
+def dcell_sim(dut):
+    yield dut.dest_i.eq(1)
+    yield dut.issue_i.eq(1)
+    yield
+    yield dut.issue_i.eq(0)
+    yield
+    yield dut.src1_i.eq(1)
+    yield dut.issue_i.eq(1)
+    yield
+    yield dut.issue_i.eq(0)
+    yield
+    yield dut.go_rd_i.eq(1)
+    yield
+    yield dut.go_rd_i.eq(0)
+    yield
+    yield dut.go_wr_i.eq(1)
+    yield
+    yield dut.go_wr_i.eq(0)
+    yield
+
+def test_dcell():
+    dut = FUDependenceCell(dummy=4, n_fu=4, n_src=2, n_dest=2)
+    vl = rtlil.convert(dut, ports=dut.ports())
+    with open("test_fu_dcell.il", "w") as f:
+        f.write(vl)
+
+    run_simulation(dut, dcell_sim(dut), vcd_name='test_fu_dcell.vcd')
+
+if __name__ == '__main__':
+    test_dcell()
-- 
2.30.2