From cbd3058c83ef97d5d4cf31a258157c86fb295a4f Mon Sep 17 00:00:00 2001 From: morgan Date: Thu, 24 Oct 2024 17:06:21 +0800 Subject: [PATCH] downconn GW: fix timing violation testing tx: add buffer to improve timing testing tx: send idle more frequently downconn GW: remove unneeded stb signal downconn GW: add docs --- src/gateware/cxp_downconn.py | 36 ++++++++++++++++++++++-------------- 1 file changed, 22 insertions(+), 14 deletions(-) diff --git a/src/gateware/cxp_downconn.py b/src/gateware/cxp_downconn.py index a414ad1..57ae8c6 100644 --- a/src/gateware/cxp_downconn.py +++ b/src/gateware/cxp_downconn.py @@ -56,9 +56,12 @@ class Receiver(Module): self.source = stream.Endpoint(word_layout) + data_valid = Signal() self.sync.cxp_gtx_rx += [ + data_valid.eq(gtx.comma_checker.rxfsm.ongoing("READY")), + self.source.stb.eq(0), - If(gtx.rx_ready & self.source.ack & ~((gtx.decoders[0].d == 0xBC) & (gtx.decoders[0].k == 1)), + If(data_valid & self.source.ack & ~((gtx.decoders[0].d == 0xBC) & (gtx.decoders[0].k == 1)), self.source.stb.eq(1), self.source.data.eq(Cat(gtx.decoders[i].d for i in range(4))), self.source.k.eq(Cat(gtx.decoders[i].k for i in range(4))), @@ -66,17 +69,22 @@ class Receiver(Module): ] # DEBUG: tx fifos for loopback - # fw -> fifo (sys) -> cdc fifo -> gtx tx + # fw -> -> cdc fifo -> buffered fifo -> gtx tx - tx_fifo = stream.AsyncFIFO(word_layout, 512) - self.submodules += ClockDomainsRenamer({"write": "sys", "read": "cxp_gtx_tx"})(tx_fifo) - self.sink = tx_fifo.sink - - self.tx_stb_sys = Signal() - txstb = Signal() - self.specials += MultiReg(self.tx_stb_sys, txstb, odomain="cxp_gtx_tx") + cdc_fifo = stream.AsyncFIFO(word_layout, 512) + self.submodules += ClockDomainsRenamer({"write": "sys", "read": "cxp_gtx_tx"})(cdc_fifo) + self.sink = cdc_fifo.sink - word_count = Signal(max=100) + # fix timing violation + cdr = ClockDomainsRenamer("cxp_gtx_tx") + self.submodules.buf = tx_fifo = cdr(stream.SyncFIFO(word_layout, 2, buffered=True)) + + self.comb += [ + cdc_fifo.source.connect(tx_fifo.sink), + ] + + idle_period = 50 # press in word + word_count = Signal(max=idle_period) # JANK: fix the every 98th word got eaten # cnt 97 98 99 0 @@ -85,11 +93,11 @@ class Receiver(Module): self.sync.cxp_gtx_tx += [ tx_fifo.source.ack.eq(0), - If(word_count == 99, + If(word_count == idle_period-1, word_count.eq(word_count.reset), ).Else( - If(tx_fifo.source.stb & txstb, - If(word_count != 98, tx_fifo.source.ack.eq(1)), + If(tx_fifo.source.stb, + If(word_count != idle_period-2, tx_fifo.source.ack.eq(1)), word_count.eq(word_count + 1), ) ) @@ -97,7 +105,7 @@ class Receiver(Module): # NOTE: prevent the first word send twice due to stream stb delay self.comb += [ - If((tx_fifo.source.stb & tx_fifo.source.ack & (word_count != 99)), + If((tx_fifo.source.stb & tx_fifo.source.ack & (word_count != idle_period-1)), gtx.encoder.d[0].eq(tx_fifo.source.data[:8]), gtx.encoder.d[1].eq(tx_fifo.source.data[8:16]), gtx.encoder.d[2].eq(tx_fifo.source.data[16:24]),