dvisampler: software controlled phase detector

build.py

@@ -46,10 +46,10 @@ NET "asfifo*/preset_empty*" TIG;
 
 NET "{dviclk0}" TNM_NET = "GRPdviclk0";
 NET "{dviclk0}" CLOCK_DEDICATED_ROUTE = FALSE;
-TIMESPEC "TSdviclk0" = PERIOD "GRPdviclk0" 22 ns HIGH 50%;
+TIMESPEC "TSdviclk0" = PERIOD "GRPdviclk0" 26.7 ns HIGH 50%;
 NET "{dviclk1}" TNM_NET = "GRPdviclk1";
 NET "{dviclk1}" CLOCK_DEDICATED_ROUTE = FALSE;
-TIMESPEC "TSdviclk1" = PERIOD "GRPdviclk1" 22 ns HIGH 50%;
+TIMESPEC "TSdviclk1" = PERIOD "GRPdviclk1" 26.7 ns HIGH 50%;
 """,
 		clk50=soc.crg.clk50_pad,
 		phy_rx_clk=soc.crg.eth_rx_clk_pad,

milkymist/dvisampler/__init__.py

@@ -7,7 +7,7 @@ from milkymist.dvisampler.clocking import Clocking
 from milkymist.dvisampler.datacapture import DataCapture
 
 class DVISampler(Module, AutoReg):
-	def __init__(self, inversions="", debug_data_capture=True):
+	def __init__(self, inversions=""):
 		self.submodules.edid = EDID()
 		self.sda = self.edid.sda
 		self.scl = self.edid.scl
@@ -17,7 +17,7 @@ class DVISampler(Module, AutoReg):
 
 		for datan in "012":
 			name = "data" + str(datan)
-			cap = DataCapture(8, debug_data_capture)
+			cap = DataCapture(8)
 			setattr(self.submodules, name + "_cap", cap)
 			if datan in inversions:
 				name += "_n"

milkymist/dvisampler/clocking.py

@@ -15,6 +15,7 @@ class Clocking(Module, AutoReg):
 		self.serdesstrobe = Signal()
 		self.clock_domains._cd_pix = ClockDomain()
 		self.clock_domains._cd_pix5x = ClockDomain()
+		self.clock_domains._cd_pix10x = ClockDomain()
 		self.clock_domains._cd_pix20x = ClockDomain()
 
 		###
@@ -24,18 +25,22 @@ class Clocking(Module, AutoReg):
 		pll_clk0 = Signal()
 		pll_clk1 = Signal()
 		pll_clk2 = Signal()
+		pll_clk3 = Signal()
 		self.specials += Instance("PLL_BASE",
-			Instance.Parameter("CLKIN_PERIOD", 22.0),
+			Instance.Parameter("CLKIN_PERIOD", 26.7),
 			Instance.Parameter("CLKFBOUT_MULT", 20),
 			Instance.Parameter("CLKOUT0_DIVIDE", 1),  # pix20x
 			Instance.Parameter("CLKOUT1_DIVIDE", 4),  # pix5x
 			Instance.Parameter("CLKOUT2_DIVIDE", 20), # pix
+			Instance.Parameter("CLKOUT3_DIVIDE", 2),  # pix10x
 			Instance.Parameter("COMPENSATION", "INTERNAL"),
 
 			Instance.Output("CLKFBOUT", clkfbout),
+			# WARNING: Do not touch the order of those clocks, or PAR fails.
 			Instance.Output("CLKOUT0", pll_clk0),
 			Instance.Output("CLKOUT1", pll_clk1),
 			Instance.Output("CLKOUT2", pll_clk2),
+			Instance.Output("CLKOUT3", pll_clk3),
 			Instance.Output("LOCKED", pll_locked),
 			Instance.Input("CLKFBIN", clkfbout),
 			Instance.Input("CLKIN", self.clkin),
@@ -56,6 +61,8 @@ class Clocking(Module, AutoReg):
 			Instance.Input("I", pll_clk1), Instance.Output("O", self._cd_pix5x.clk))
 		self.specials += Instance("BUFG",
 			Instance.Input("I", pll_clk2), Instance.Output("O", self._cd_pix.clk))
+		self.specials += Instance("BUFG",
+			Instance.Input("I", pll_clk3), Instance.Output("O", self._cd_pix10x.clk))
 		self.specials += MultiReg(locked_async, self.locked, "sys")
 		self.comb += self._r_locked.field.w.eq(self.locked)
 

milkymist/dvisampler/datacapture.py

@@ -5,14 +5,16 @@ from migen.genlib.cdc import MultiReg, PulseSynchronizer
 from migen.bank.description import *
 
 class DataCapture(Module, AutoReg):
-	def __init__(self, ntbits, debug=False):
+	def __init__(self, ntbits):
 		self.pad = Signal()
 		self.serdesstrobe = Signal()
 		self.d0 = Signal() # pix5x clock domain
 		self.d1 = Signal() # pix5x clock domain
 
-		if debug:
+		self._r_dly_ctl = RegisterRaw(4)
-			self._r_current_tap = RegisterField(8, READ_ONLY, WRITE_ONLY)
+		self._r_dly_busy = RegisterField(1, READ_ONLY, WRITE_ONLY)
+		self._r_phase = RegisterField(2, READ_ONLY, WRITE_ONLY)
+		self._r_phase_reset = RegisterRaw()
 
 		###
 
@@ -20,19 +22,23 @@ class DataCapture(Module, AutoReg):
 		pad_delayed = Signal()
 		delay_inc = Signal()
 		delay_ce = Signal()
+		delay_cal = Signal()
+		delay_rst = Signal()
+		delay_busy = Signal()
 		self.specials += Instance("IODELAY2",
 			Instance.Parameter("DELAY_SRC", "IDATAIN"),
-			Instance.Parameter("IDELAY_TYPE", "VARIABLE_FROM_ZERO"),
+			Instance.Parameter("IDELAY_TYPE", "VARIABLE_FROM_HALF_MAX"),
 			Instance.Parameter("COUNTER_WRAPAROUND", "STAY_AT_LIMIT"),
 			Instance.Parameter("DATA_RATE", "SDR"),
 			Instance.Input("IDATAIN", self.pad),
 			Instance.Output("DATAOUT", pad_delayed),
+			Instance.Input("CLK", ClockSignal("pix5x")),
+			Instance.Input("IOCLK0", ClockSignal("pix10x")),
 			Instance.Input("INC", delay_inc),
 			Instance.Input("CE", delay_ce),
-			Instance.Input("RST", ResetSignal("pix5x")),
+			Instance.Input("CAL", delay_cal),
-			Instance.Input("CLK", ClockSignal("pix5x")),
+			Instance.Input("RST", delay_rst),
-			Instance.Input("IOCLK0", ClockSignal("pix20x")),
+			Instance.Output("BUSY", delay_busy),
-			Instance.Input("CAL", 0),
 			Instance.Input("T", 1)
 		)
 
@@ -57,23 +63,19 @@ class DataCapture(Module, AutoReg):
 			Instance.Input("RST", 0)
 		)
 
-		# Transition counter
+		# Phase detector
-		transitions = Signal(ntbits)
+		lateness = Signal(ntbits, reset=2**(ntbits - 1))
-		lateness = Signal((ntbits + 1, True))
+		too_late = Signal()
-		pulse_inc = Signal()
+		too_early = Signal()
-		pulse_dec = Signal()
+		reset_lateness = Signal()
+		self.comb += [
+			too_late.eq(lateness == (2**ntbits - 1)),
+			too_early.eq(lateness == 0)
+		]
 		self.sync.pix5x += [
-			pulse_inc.eq(0),
+			If(reset_lateness,
-			pulse_dec.eq(0),
+				lateness.eq(2**(ntbits - 1))
-			If(transitions ==  2**ntbits - 1,
+			).Elif(~delay_busy & ~too_late & ~too_early & (self.d0 != self.d1),
-				If(lateness[ntbits],
-					pulse_inc.eq(1)
-				).Else(
-					pulse_dec.eq(1)
-				),
-				lateness.eq(0),
-				transitions.eq(0)
-			).Elif(self.d0 != self.d1,
 				If(self.d0,
 					# 1 -----> 0
 					#    d0p
@@ -90,39 +92,57 @@ class DataCapture(Module, AutoReg):
 					).Else(
 						lateness.eq(lateness - 1)
 					)
-				),
+				)
-				transitions.eq(transitions + 1)
 			)
 		]
 
-		# Drive IODELAY controls
+		# Delay control
-		delay_init = Signal()
+		self.submodules.delay_done = PulseSynchronizer("pix5x", "sys")
-		delay_init_count = Signal(7, reset=127)
+		delay_pending = Signal()
-		self.comb += delay_init.eq(delay_init_count != 0)
+		self.sync.pix5x += [
-		self.sync.pix5x += If(delay_init, delay_init_count.eq(delay_init_count - 1))
+			self.delay_done.i.eq(0),
-		self.comb += [
+			If(~delay_pending,
-			delay_ce.eq(delay_init | pulse_inc | pulse_dec),
+				If(delay_cal | delay_ce, delay_pending.eq(1))
-			delay_inc.eq(delay_init | pulse_inc)
+			).Else(
+				If(~delay_busy,
+					self.delay_done.i.eq(1),
+					delay_pending.eq(0)
+				)
+			)
 		]
 
-		# Debug
+		self.submodules.do_delay_cal = PulseSynchronizer("sys", "pix5x")
-		if debug:
+		self.submodules.do_delay_rst = PulseSynchronizer("sys", "pix5x")
-			# Transfer delay update commands to system clock domain
+		self.submodules.do_delay_inc = PulseSynchronizer("sys", "pix5x")
-			pix5x_reset_sys = Signal()
+		self.submodules.do_delay_dec = PulseSynchronizer("sys", "pix5x")
-			self.specials += MultiReg(ResetSignal("pix5x"), pix5x_reset_sys, "sys")
+		self.comb += [
-			self.submodules.xf_inc = PulseSynchronizer("pix5x", "sys")
+			delay_cal.eq(self.do_delay_cal.o),
-			self.submodules.xf_dec = PulseSynchronizer("pix5x", "sys")
+			delay_rst.eq(self.do_delay_rst.o),
-			self.comb += [
+			delay_inc.eq(self.do_delay_inc.o),
-				self.xf_inc.i.eq(pulse_inc),
+			delay_ce.eq(self.do_delay_inc.o | self.do_delay_dec.o),
-				self.xf_dec.i.eq(pulse_dec)
+		]
-			]
+
-			# Update tap count in system clock domain
+		sys_delay_pending = Signal()
-			current_tap = Signal(8, reset=127)
+		self.sync += [
-			self.comb += self._r_current_tap.field.w.eq(current_tap)
+			If(self.do_delay_cal.i | self.do_delay_inc.i | self.do_delay_dec.i,
-			self.sync += If(pix5x_reset_sys,
+				sys_delay_pending.eq(1)
-					current_tap.eq(127)
+			).Elif(self.delay_done.o,
-				).Elif(self.xf_inc.o & (current_tap != 0xff),
+				sys_delay_pending.eq(0)
-					current_tap.eq(current_tap + 1)
+			)
-				).Elif(self.xf_dec.o & (current_tap != 0),
+		]
-					current_tap.eq(current_tap - 1)
+
-				)
+		self.comb += [
+			self.do_delay_cal.i.eq(self._r_dly_ctl.re & self._r_dly_ctl.r[0]),
+			self.do_delay_rst.i.eq(self._r_dly_ctl.re & self._r_dly_ctl.r[1]),
+			self.do_delay_inc.i.eq(self._r_dly_ctl.re & self._r_dly_ctl.r[2]),
+			self.do_delay_dec.i.eq(self._r_dly_ctl.re & self._r_dly_ctl.r[3]),
+			self._r_dly_busy.field.w.eq(sys_delay_pending)
+		]
+
+		# Phase detector control
+		self.specials += MultiReg(Cat(too_late, too_early), self._r_phase.field.w)
+		self.submodules.do_reset_lateness = PulseSynchronizer("sys", "pix5x")
+		self.comb += [
+			reset_lateness.eq(self.do_reset_lateness.o),
+			self.do_reset_lateness.i.eq(self._r_phase_reset.re)
+		]