From a5be2cd2576a0d2ba5e5c1bd3a5a609bef7431eb Mon Sep 17 00:00:00 2001 From: =?utf8?q?J=C4=99drzej=20Boczar?= Date: Wed, 15 Jul 2020 11:28:21 +0200 Subject: [PATCH] soc/interconnect/axi: improve SRAM/CSR access speed --- litex/soc/interconnect/axi.py | 187 ++++++++++++++-------------------- 1 file changed, 75 insertions(+), 112 deletions(-) diff --git a/litex/soc/interconnect/axi.py b/litex/soc/interconnect/axi.py index a9ee719c..1fc7af8a 100644 --- a/litex/soc/interconnect/axi.py +++ b/litex/soc/interconnect/axi.py @@ -497,6 +497,69 @@ class Wishbone2AXILite(Module): # AXILite to CSR ----------------------------------------------------------------------------------- +def axi_lite_to_simple(axi_lite, port_adr, port_dat_r, port_dat_w=None, port_we=None): + """Connection of AXILite to simple bus with 1-cycle latency, such as CSR bus or Memory port""" + bus_data_width = axi_lite.data_width + adr_shift = log2_int(bus_data_width//8) + do_read = Signal() + do_write = Signal() + last_was_read = Signal() + + comb = [] + if port_dat_w is not None: + comb.append(port_dat_w.eq(axi_lite.w.data)) + if port_we is not None: + if len(port_we) > 1: + for i in range(bus_data_width//8): + comb.append(port_we[i].eq(axi_lite.w.valid & axi_lite.w.ready & axi_lite.w.strb[i])) + else: + comb.append(port_we.eq(axi_lite.w.valid & axi_lite.w.ready & (axi_lite.w.strb != 0))) + + fsm = FSM() + fsm.act("START-TRANSACTION", + # If the last access was a read, do a write, and vice versa + If(axi_lite.aw.valid & axi_lite.ar.valid, + do_write.eq(last_was_read), + do_read.eq(~last_was_read), + ).Else( + do_write.eq(axi_lite.aw.valid), + do_read.eq(axi_lite.ar.valid), + ), + # Start reading/writing immediately not to waste a cycle + If(do_write, + port_adr.eq(axi_lite.aw.addr[adr_shift:]), + If(axi_lite.w.valid, + axi_lite.aw.ready.eq(1), + axi_lite.w.ready.eq(1), + NextState("SEND-WRITE-RESPONSE") + ) + ).Elif(do_read, + port_adr.eq(axi_lite.ar.addr[adr_shift:]), + axi_lite.ar.ready.eq(1), + NextState("SEND-READ-RESPONSE"), + ) + ) + fsm.act("SEND-READ-RESPONSE", + NextValue(last_was_read, 1), + # As long as we have correct address port.dat_r will be valid + port_adr.eq(axi_lite.ar.addr[adr_shift:]), + axi_lite.r.data.eq(port_dat_r), + axi_lite.r.resp.eq(RESP_OKAY), + axi_lite.r.valid.eq(1), + If(axi_lite.r.ready, + NextState("START-TRANSACTION") + ) + ) + fsm.act("SEND-WRITE-RESPONSE", + NextValue(last_was_read, 0), + axi_lite.b.valid.eq(1), + axi_lite.b.resp.eq(RESP_OKAY), + If(axi_lite.b.ready, + NextState("START-TRANSACTION") + ) + ) + return fsm, comb + class AXILite2CSR(Module): def __init__(self, axi_lite=None, csr=None): if axi_lite is None: @@ -507,64 +570,11 @@ class AXILite2CSR(Module): self.axi_lite = axi_lite self.csr = csr - adr_shift = log2_int(self.axi_lite.data_width//8) - rdata = Signal.like(self.csr.dat_r) - do_read = Signal() - do_write = Signal() - last_was_read = Signal() - - # # # - - self.submodules.fsm = fsm = FSM() - fsm.act("IDLE", - # if last access was a read, do a write, and vice versa - If(self.axi_lite.aw.valid & self.axi_lite.ar.valid, - do_write.eq(last_was_read), - do_read.eq(~last_was_read), - ).Else( - do_write.eq(self.axi_lite.aw.valid), - do_read.eq(self.axi_lite.ar.valid), - ), - If(do_write, - NextValue(last_was_read, 0), - NextState("DO-WRITE"), - ).Elif(do_read, - self.csr.adr.eq(self.axi_lite.ar.addr[adr_shift:]), - self.csr.we.eq(0), - NextValue(last_was_read, 1), - NextState("DO-READ"), - ) - ) - fsm.act("DO-READ", - self.axi_lite.ar.ready.eq(1), - NextValue(rdata, self.csr.dat_r), - NextState("SEND-READ-RESPONSE"), - ) - fsm.act("SEND-READ-RESPONSE", - self.axi_lite.r.valid.eq(1), - self.axi_lite.r.resp.eq(RESP_OKAY), - self.axi_lite.r.data.eq(rdata), - If(self.axi_lite.r.ready, - NextState("IDLE") - ) - ) - fsm.act("DO-WRITE", - self.csr.adr.eq(self.axi_lite.aw.addr[adr_shift:]), - self.csr.dat_w.eq(self.axi_lite.w.data), - If(self.axi_lite.w.valid, - self.csr.we.eq(1 & (self.axi_lite.w.strb != 0)), - self.axi_lite.aw.ready.eq(1), - self.axi_lite.w.ready.eq(1), - NextState("SEND-WRITE-RESPONSE") - ) - ) - fsm.act("SEND-WRITE-RESPONSE", - self.axi_lite.b.valid.eq(1), - self.axi_lite.b.resp.eq(RESP_OKAY), - If(self.axi_lite.b.ready, - NextState("IDLE") - ) - ) + fsm, comb = axi_lite_to_simple(self.axi_lite, + port_adr=self.csr.adr, port_dat_r=self.csr.dat_r, + port_dat_w=self.csr.dat_w, port_we=self.csr.we) + self.submodules.fsm = fsm + self.comb += comb # AXILite SRAM ------------------------------------------------------------------------------------- @@ -600,57 +610,10 @@ class AXILiteSRAM(Module): self.comb += [port.we[i].eq(self.bus.w.valid & self.bus.w.ready & self.bus.w.strb[i]) for i in range(bus_data_width//8)] - # Access logic - adr_shift = log2_int(self.bus.data_width//8) - rdata = Signal.like(port.dat_r) - do_read = Signal() - do_write = Signal() - last_was_read = Signal() - - self.submodules.fsm = fsm = FSM(reset_state="IDLE") - fsm.act("IDLE", - # if last access was a read, do a write, and vice versa - If(self.bus.aw.valid & self.bus.ar.valid, - do_write.eq(last_was_read), - do_read.eq(~last_was_read), - ).Else( - do_write.eq(self.bus.aw.valid), - do_read.eq(self.bus.ar.valid), - ), - If(do_write, - NextValue(last_was_read, 0), - NextState("DO-WRITE"), - ).Elif(do_read, - port.adr.eq(self.bus.ar.addr[adr_shift:]), - NextValue(last_was_read, 1), - NextState("DO-READ"), - ) - ) - fsm.act("DO-READ", - self.bus.ar.ready.eq(1), - NextValue(rdata, port.dat_r), - NextState("SEND-READ-RESPONSE"), - ) - fsm.act("SEND-READ-RESPONSE", - self.bus.r.valid.eq(1), - self.bus.r.resp.eq(RESP_OKAY), - self.bus.r.data.eq(rdata), - If(self.bus.r.ready, - NextState("IDLE") - ) - ) - fsm.act("DO-WRITE", - port.adr.eq(self.bus.aw.addr[adr_shift:]), - If(self.bus.w.valid, - self.bus.aw.ready.eq(1), - self.bus.w.ready.eq(1), - NextState("SEND-WRITE-RESPONSE") - ) - ) - fsm.act("SEND-WRITE-RESPONSE", - self.bus.b.valid.eq(1), - self.bus.b.resp.eq(RESP_OKAY), - If(self.bus.b.ready, - NextState("IDLE") - ) - ) + # Transaction logic + fsm, comb = axi_lite_to_simple(self.bus, + port_adr=port.adr, port_dat_r=port.dat_r, + port_dat_w=port.dat_w if not read_only else None, + port_we=port.we if not read_only else None) + self.submodules.fsm = fsm + self.comb += comb -- 2.30.2