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frontend/axi: optimize burst2beat timings

This commit is contained in:
Florent Kermarrec 2018-09-18 19:01:41 +02:00
parent 6941285d3f
commit e6ef89a4d3
1 changed files with 14 additions and 12 deletions
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26
litedram/frontend/axi.py
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@ -88,7 +88,8 @@ class LiteDRAMAXIBurst2Beat(Module):
# convert burst size to bytes # convert burst size to bytes
cases = {} cases = {}
for i in range(11): cases["default"] = size.eq(1024)
for i in range(10):
cases[i] = size.eq(2**i) cases[i] = size.eq(2**i)
self.comb += Case(ax_burst.size, cases) self.comb += Case(ax_burst.size, cases)
@ -101,17 +102,19 @@ class LiteDRAMAXIBurst2Beat(Module):
ax_beat.id.eq(ax_burst.id), ax_beat.id.eq(ax_burst.id),
If(ax_beat.valid & ax_beat.ready, If(ax_beat.valid & ax_beat.ready,
If(ax_burst.len != 0, If(ax_burst.len != 0,
NextValue(count, 0),
NextValue(offset, size),
NextState("BURST2BEAT") NextState("BURST2BEAT")
).Else( ).Else(
ax_burst.ready.eq(1) ax_burst.ready.eq(1)
) )
) ),
NextValue(count, 1),
NextValue(offset, size),
) )
wrap_offset = Signal(8 + 4)
self.sync += wrap_offset.eq((ax_burst.len - 1)*size)
fsm.act("BURST2BEAT", fsm.act("BURST2BEAT",
ax_beat.valid.eq(1), ax_beat.valid.eq(1),
ax_beat.last.eq(count == (ax_burst.len - 1)), ax_beat.last.eq(count == ax_burst.len),
If((ax_burst.burst == burst_types["incr"]) | If((ax_burst.burst == burst_types["incr"]) |
(ax_burst.burst == burst_types["wrap"]), (ax_burst.burst == burst_types["wrap"]),
ax_beat.addr.eq(ax_burst.addr + offset) ax_beat.addr.eq(ax_burst.addr + offset)
@ -123,13 +126,12 @@ class LiteDRAMAXIBurst2Beat(Module):
If(ax_beat.last, If(ax_beat.last,
ax_burst.ready.eq(1), ax_burst.ready.eq(1),
NextState("IDLE") NextState("IDLE")
).Else( ),
NextValue(count, count + 1), NextValue(count, count + 1),
NextValue(offset, offset + size), NextValue(offset, offset + size),
If(ax_burst.burst == burst_types["wrap"], If(ax_burst.burst == burst_types["wrap"],
If(offset == (ax_burst.len - 1)*size, If(offset == wrap_offset,
NextValue(offset, 0) NextValue(offset, 0)
)
) )
) )
) )