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cores/hyperbus: Cleanup fixed/variable latency support.

This commit is contained in:
Florent Kermarrec 2024-04-15 14:05:39 +02:00
parent 93f76ede95
commit 6e00cfa9d0
1 changed files with 10 additions and 32 deletions
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38
litex/soc/cores/hyperbus.py
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@ -52,8 +52,6 @@ class HyperRAM(LiteXModule):
if with_csr:
self.add_csr(default_latency=latency)
self.reg_debug = CSRStatus(32)
# # #
clk = Signal()
@ -150,13 +148,6 @@ class HyperRAM(LiteXModule):
self.reg_read_done.eq(reg_read_done),
]
self.comb += [
self.reg_debug.status[0].eq(reg_write_req),
self.reg_debug.status[1].eq(reg_write_done),
self.reg_debug.status[2].eq(reg_read_req),
self.reg_debug.status[3].eq(reg_read_done),
]
# Command generation -----------------------------------------------------------------------
ashift = {8:1, 16:0}[dw]
self.comb += [
@ -179,11 +170,6 @@ class HyperRAM(LiteXModule):
)
]
# Latency count starts from the middle of the command (thus the -4). In fixed latency mode
# (default), latency is 2 x Latency count. We have 4 x sys_clk per RAM clock:
latency_cycles_0 = (self.latency * 4)
latency_cycles_1 = (self.latency * 4) - 4
# Bus Latch --------------------------------------------------------------------------------
bus_adr = Signal(32)
bus_we = Signal()
@ -201,6 +187,7 @@ class HyperRAM(LiteXModule):
# FSM (Sequencer) --------------------------------------------------------------------------
cycles = Signal(8)
first = Signal()
refresh = Signal()
self.fsm = fsm = FSM(reset_state="IDLE")
fsm.act("IDLE",
NextValue(first, 1),
@ -223,11 +210,9 @@ class HyperRAM(LiteXModule):
NextValue(sr, Cat(Signal(40), self.reg_write_data[8:])),
NextState("REG-WRITE-0")
).Else(
If((latency_mode in ["fixed"]) | rwds.i,
NextState("WAIT-LATENCY-0")
).Else(
NextState("WAIT-LATENCY-1")
)
# Sample RWDS to know if 1X/2X Latency should be used (Refresh).
NextValue(refresh, rwds.i | (latency_mode in ["fixed"])),
NextState("WAIT-LATENCY")
)
)
)
@ -256,19 +241,12 @@ class HyperRAM(LiteXModule):
NextState("IDLE")
)
)
fsm.act("WAIT-LATENCY-0",
fsm.act("WAIT-LATENCY",
# Set CSn.
cs.eq(1),
# Wait for Latency cycles...
If(cycles == (latency_cycles_0 - 1),
NextState("WAIT-LATENCY-1")
)
)
fsm.act("WAIT-LATENCY-1",
# Set CSn.
cs.eq(1),
# Wait for Latency cycles...
If(cycles == (latency_cycles_1 - 1),
# Wait for 1X or 2X Latency cycles... (-4 since count start in the middle of the command).
If(((cycles == 2*(self.latency * 4) - 4 - 1) & refresh) | # 2X Latency (No DRAM refresh required).
((cycles == 1*(self.latency * 4) - 4 - 1) & ~refresh) , # 1X Latency ( DRAM refresh required).
# Latch Bus.
bus_latch.eq(1),
# Early Write Ack (to allow bursting).