artiq-zynq/src/gateware/zynq_clocking.py

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from migen import *
from migen.genlib.cdc import MultiReg
from migen.genlib.resetsync import AsyncResetSynchronizer
from misoc.interconnect.csr import *
class ClockSwitchFSM(Module):
def __init__(self):
self.i_clk_sw = Signal()
self.o_clk_sw = Signal()
self.o_reset = Signal()
###
i_switch = Signal()
o_switch = Signal()
reset = Signal()
# at 125MHz bootstrap cd, will get around 0.5ms
delay_counter = Signal(16, reset=0xFFFF)
# register to prevent glitches
self.sync.bootstrap += [
self.o_clk_sw.eq(o_switch),
self.o_reset.eq(reset),
]
self.o_clk_sw.attr.add("no_retiming")
self.o_reset.attr.add("no_retiming")
self.i_clk_sw.attr.add("no_retiming")
i_switch.attr.add("no_retiming")
self.specials += MultiReg(self.i_clk_sw, i_switch, "bootstrap")
fsm = ClockDomainsRenamer("bootstrap")(FSM(reset_state="START"))
self.submodules += fsm
fsm.act("START",
If(i_switch & ~o_switch,
NextState("RESET_START"))
)
fsm.act("RESET_START",
reset.eq(1),
If(delay_counter == 0,
NextValue(delay_counter, 0xFFFF),
NextState("CLOCK_SWITCH")
).Else(
NextValue(delay_counter, delay_counter-1),
)
)
fsm.act("CLOCK_SWITCH",
reset.eq(1),
NextValue(o_switch, 1),
NextValue(delay_counter, delay_counter-1),
If(delay_counter == 0,
NextState("END"))
)
fsm.act("END",
NextValue(o_switch, 1),
reset.eq(0))
class SYSCRG(Module, AutoCSR):
def __init__(self, platform, ps7, main_clk, clk_sw=None, freq=125e6):
# assumes bootstrap clock is same freq as main and sys output
self.clock_domains.cd_sys = ClockDomain()
self.clock_domains.cd_sys4x = ClockDomain(reset_less=True)
self.current_clock = CSRStatus()
self.cd_sys.clk.attr.add("keep")
bootstrap_clk = ClockSignal("bootstrap")
period = 1e9/freq
pll_locked = Signal()
pll_sys = Signal()
pll_sys4x = Signal()
fb_clk = Signal()
self.submodules.clk_sw_fsm = ClockSwitchFSM()
if clk_sw is None:
self.clock_switch = CSRStorage()
self.comb += self.clk_sw_fsm.i_clk_sw.eq(self.clock_switch.storage)
else:
self.comb += self.clk_sw_fsm.i_clk_sw.eq(clk_sw)
self.specials += [
Instance("PLLE2_ADV",
p_STARTUP_WAIT="FALSE", o_LOCKED=pll_locked,
p_BANDWIDTH="HIGH",
p_REF_JITTER1=0.001,
p_CLKIN1_PERIOD=period, i_CLKIN1=main_clk,
p_CLKIN2_PERIOD=period, i_CLKIN2=bootstrap_clk,
i_CLKINSEL=self.clk_sw_fsm.o_clk_sw,
# VCO @ 1.5GHz when using 125MHz input
# 1.2GHz for 100MHz (zc706)
p_CLKFBOUT_MULT=12, p_DIVCLK_DIVIDE=1,
i_CLKFBIN=fb_clk,
i_RST=self.clk_sw_fsm.o_reset,
o_CLKFBOUT=fb_clk,
p_CLKOUT0_DIVIDE=3, p_CLKOUT0_PHASE=0.0,
o_CLKOUT0=pll_sys4x,
p_CLKOUT1_DIVIDE=12, p_CLKOUT1_PHASE=0.0,
o_CLKOUT1=pll_sys),
Instance("BUFG", i_I=pll_sys, o_O=self.cd_sys.clk),
Instance("BUFG", i_I=pll_sys4x, o_O=self.cd_sys4x.clk),
AsyncResetSynchronizer(self.cd_sys, ~pll_locked),
]
self.comb += self.current_clock.status.eq(self.clk_sw_fsm.o_clk_sw)