from nmutil.latch import SRLatch
+class DepCell(Elaboratable):
+ """ implements 11.4.7 mitch alsup dependence cell, p27
+ adjusted to be clock-sync'd on rising edge only.
+ mitch design (as does 6600) requires alternating rising/falling clock
+
+ * SET mode: issue_i HI, go_i LO, reg_i HI - register is captured
+ - FWD is DISABLED (~issue_i)
+ - RSEL DISABLED
+ * QRY mode: issue_i LO, go_i LO, haz_i HI - FWD is ASSERTED
+ reg_i HI - ignored
+ * GO mode : issue_i LO, go_i HI - RSEL is ASSERTED
+ haz_i HI - FWD still can be ASSERTED
+
+ FWD assertion (hazard protection) therefore still occurs in both
+ Query and Go Modes, for this cycle, due to the cq register
+
+ GO mode works for one cycle, again due to the cq register capturing
+ the latch output. Without the cq register, the SR Latch (which is
+ asynchronous) would be reset at the exact moment that GO was requested,
+ and the RSEL would be garbage.
+ """
+ def __init__(self):
+ # inputs
+ self.reg_i = Signal(reset_less=True) # reg bit in (top)
+ self.issue_i = Signal(reset_less=True) # Issue in (top)
+ self.hazard_i = Signal(reset_less=True) # to check hazard
+ self.go_i = Signal(reset_less=True) # Go read/write in (left)
+ self.q_o = Signal(reset_less=True) # Latch out (register active)
+
+ # for Register File Select Lines (vertical)
+ self.rsel_o = Signal(reset_less=True) # reg sel (bottom)
+ # for Function Unit "forward progress" (horizontal)
+ self.fwd_o = Signal(reset_less=True) # FU forard progress (right)
+
+ def elaborate(self, platform):
+ m = Module()
+ m.submodules.l = l = SRLatch(sync=False) # async latch
+
+ # record current version of q in a sync'd register
+ cq = Signal() # resets to 0
+ m.d.sync += cq.eq(l.q)
+
+ # reset on go HI, set on dest and issue
+ m.d.comb += l.s.eq(self.issue_i & self.reg_i)
+ m.d.comb += l.r.eq(self.go_i)
+
+ # Function Unit "Forward Progress".
+ m.d.comb += self.fwd_o.eq((l.q) & self.hazard_i & ~self.issue_i)
+
+ # Register Select. Activated on go read/write and *current* latch set
+ m.d.comb += self.rsel_o.eq((cq | l.q) & self.go_i)
+
+ m.d.comb += self.q_o.eq(cq | l.q)
+
+ return m
+
+ def __iter__(self):
+ yield self.reg_i
+ yield self.hazard_i
+ yield self.issue_i
+ yield self.go_i
+ yield self.q_o
+ yield self.rsel_o
+ yield self.fwd_o
+
+ def ports(self):
+ return list(self)
+
+
class DependenceCell(Elaboratable):
""" implements 11.4.7 mitch alsup dependence cell, p27
"""
self.src2_i = Signal(reset_less=True) # oper2 in (top)
self.issue_i = Signal(reset_less=True) # Issue in (top)
+ self.rd_pend_i = Signal(reset_less=True) # Read pending in (top)
+ self.wr_pend_i = Signal(reset_less=True) # Write pending in (top)
+ self.rd_rsel_o = Signal(reset_less=True) # Read pending out (bottom)
+ self.wr_rsel_o = Signal(reset_less=True) # Write pending out (bottom)
+
self.go_wr_i = Signal(reset_less=True) # Go Write in (left)
self.go_rd_i = Signal(reset_less=True) # Go Read in (left)
def elaborate(self, platform):
m = Module()
- m.submodules.dest_l = dest_l = SRLatch(sync=False) # clock-sync'd
- m.submodules.src1_l = src1_l = SRLatch(sync=False) # clock-sync'd
- m.submodules.src2_l = src2_l = SRLatch(sync=False) # clock-sync'd
-
- # destination latch: reset on go_wr HI, set on dest and issue
- m.d.comb += dest_l.s.eq(self.issue_i & self.dest_i)
- m.d.comb += dest_l.r.eq(self.go_wr_i)
-
- # src1 latch: reset on go_rd HI, set on src1_i and issue
- m.d.comb += src1_l.s.eq(self.issue_i & self.src1_i)
- m.d.comb += src1_l.r.eq(self.go_rd_i)
-
- # src2 latch: reset on go_rd HI, set on op2_i and issue
- m.d.comb += src2_l.s.eq(self.issue_i & self.src2_i)
- m.d.comb += src2_l.r.eq(self.go_rd_i)
-
- # FU "Forward Progress" (read out horizontally)
- m.d.comb += self.dest_fwd_o.eq(dest_l.q & self.go_wr_i)
- m.d.comb += self.src1_fwd_o.eq(src1_l.q & self.go_rd_i)
- m.d.comb += self.src2_fwd_o.eq(src2_l.q & self.go_rd_i)
-
- # Register File Select (read out vertically)
- m.d.sync += self.dest_rsel_o.eq(dest_l.q & self.dest_i)
- m.d.sync += self.src1_rsel_o.eq(src1_l.q & self.src1_i)
- m.d.sync += self.src2_rsel_o.eq(src2_l.q & self.src2_i)
+ m.submodules.dest_c = dest_c = DepCell()
+ m.submodules.src1_c = src1_c = DepCell()
+ m.submodules.src2_c = src2_c = DepCell()
+
+ # connect issue
+ for c in [dest_c, src1_c, src2_c]:
+ m.d.comb += c.issue_i.eq(self.issue_i)
+
+ # connect go_rd / go_wr (dest->wr, src->rd)
+ m.d.comb += dest_c.go_i.eq(self.go_wr_i)
+ m.d.comb += src1_c.go_i.eq(self.go_rd_i)
+ m.d.comb += src2_c.go_i.eq(self.go_rd_i)
+
+ # connect input reg bit (unary)
+ for c, reg in [(dest_c, self.dest_i),
+ (src1_c, self.src1_i),
+ (src2_c, self.src2_i)]:
+ m.d.comb += c.reg_i.eq(reg)
+
+ # wark-wark: yes, writing to the same reg you are reading is *NOT*
+ # a write-after-read hazard.
+ selfhazard = Signal(reset_less=False)
+ m.d.comb += selfhazard.eq((self.dest_i & self.src1_i) |
+ (self.dest_i & self.src2_i))
+
+ # connect up hazard checks: read-after-write and write-after-read
+ m.d.comb += dest_c.hazard_i.eq(self.rd_pend_i) # read-after-write
+ m.d.comb += src1_c.hazard_i.eq(self.wr_pend_i) # write-after-read
+ m.d.comb += src2_c.hazard_i.eq(self.wr_pend_i) # write-after-read
+
+ # connect fwd / reg-sel outputs
+ for c, fwd, rsel in [(dest_c, self.dest_fwd_o, self.dest_rsel_o),
+ (src1_c, self.src1_fwd_o, self.src1_rsel_o),
+ (src2_c, self.src2_fwd_o, self.src2_rsel_o)]:
+ m.d.comb += fwd.eq(c.fwd_o)
+ m.d.comb += rsel.eq(c.rsel_o)
+
+ # to be accumulated to indicate if register is in use (globally)
+ # after ORing, is fed back in to rd_pend_i / wr_pend_i
+ m.d.comb += self.rd_rsel_o.eq(src1_c.q_o | src2_c.q_o)
+ #with m.If(~selfhazard):
+ m.d.comb += self.wr_rsel_o.eq(dest_c.q_o)
return m
yield self.dest_i
yield self.src1_i
yield self.src2_i
+ yield self.rd_pend_i
+ yield self.wr_pend_i
yield self.issue_i
yield self.go_wr_i
yield self.go_rd_i
self.src1_i = Signal(n_reg_col, reset_less=True)
self.src2_i = Signal(n_reg_col, reset_less=True)
+ self.rd_pend_i = Signal(n_reg_col, reset_less=True)
+ self.wr_pend_i = Signal(n_reg_col, reset_less=True)
+
+ self.rd_rsel_o = Signal(n_reg_col, reset_less=True)
+ self.wr_rsel_o = Signal(n_reg_col, reset_less=True)
+
self.issue_i = Signal(reset_less=True)
self.go_wr_i = Signal(reset_less=True)
self.go_rd_i = Signal(reset_less=True)
# ---
# connect Dep dest/src to module dest/src
# ---
+ rd_pend_i = []
+ wr_pend_i = []
+ rd_rsel_o = []
+ wr_rsel_o = []
dest_i = []
src1_i = []
src2_i = []
for rn in range(self.n_reg_col):
dc = rcell[rn]
# accumulate cell inputs dest/src1/src2
+ rd_pend_i.append(dc.rd_pend_i)
+ wr_pend_i.append(dc.wr_pend_i)
+ rd_rsel_o.append(dc.rd_rsel_o)
+ wr_rsel_o.append(dc.wr_rsel_o)
dest_i.append(dc.dest_i)
src1_i.append(dc.src1_i)
src2_i.append(dc.src2_i)
m.d.comb += [Cat(*dest_i).eq(self.dest_i),
Cat(*src1_i).eq(self.src1_i),
Cat(*src2_i).eq(self.src2_i),
+ Cat(*rd_pend_i).eq(self.rd_pend_i),
+ Cat(*wr_pend_i).eq(self.wr_pend_i),
+ self.rd_rsel_o.eq(Cat(*rd_rsel_o)),
+ self.wr_rsel_o.eq(Cat(*wr_rsel_o)),
]
# ---
projects / soc.git / blobdiff