litex/migen/bank/csrgen.py

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from migen.fhdl.structure import *
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from migen.bus import csr
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from migen.bank.description import *
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class Bank:
def __init__(self, description, address=0, bus=None):
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self.description = description
self.address = address
if bus is None:
bus = csr.Interface()
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self.bus = bus
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def get_fragment(self):
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comb = []
sync = []
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sel = Signal()
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comb.append(sel.eq(self.bus.adr[9:] == self.address))
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desc_exp = expand_description(self.description, csr.data_width)
nbits = bits_for(len(desc_exp)-1)
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# Bus writes
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bwcases = {}
for i, reg in enumerate(desc_exp):
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if isinstance(reg, RegisterRaw):
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comb.append(reg.r.eq(self.bus.dat_w[:reg.size]))
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comb.append(reg.re.eq(sel & \
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self.bus.we & \
(self.bus.adr[:nbits] == i)))
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elif isinstance(reg, RegisterFields):
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bwra = []
offset = 0
for field in reg.fields:
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if field.access_bus == WRITE_ONLY or field.access_bus == READ_WRITE:
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bwra.append(field.storage.eq(self.bus.dat_w[offset:offset+field.size]))
offset += field.size
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if bwra:
bwcases[i] = bwra
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# commit atomic writes
for field in reg.fields:
if isinstance(field, FieldAlias) and field.commit_list:
commit_instr = [hf.commit_to.eq(hf.storage) for hf in field.commit_list]
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sync.append(If(sel & self.bus.we & self.bus.adr[:nbits] == i, *commit_instr))
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else:
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raise TypeError
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if bwcases:
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sync.append(If(sel & self.bus.we, Case(self.bus.adr[:nbits], bwcases)))
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# Bus reads
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brcases = {}
for i, reg in enumerate(desc_exp):
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if isinstance(reg, RegisterRaw):
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brcases[i] = [self.bus.dat_r.eq(reg.w)]
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elif isinstance(reg, RegisterFields):
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brs = []
reg_readable = False
for field in reg.fields:
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if field.access_bus == READ_ONLY or field.access_bus == READ_WRITE:
brs.append(field.storage)
reg_readable = True
else:
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brs.append(Replicate(0, field.size))
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if reg_readable:
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brcases[i] = [self.bus.dat_r.eq(Cat(*brs))]
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else:
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raise TypeError
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if brcases:
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sync.append(self.bus.dat_r.eq(0))
sync.append(If(sel, Case(self.bus.adr[:nbits], brcases)))
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else:
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comb.append(self.bus.dat_r.eq(0))
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# Device access
for reg in self.description:
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if isinstance(reg, RegisterFields):
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for field in reg.fields:
if field.access_bus == READ_ONLY and field.access_dev == WRITE_ONLY:
comb.append(field.storage.eq(field.w))
else:
if field.access_dev == READ_ONLY or field.access_dev == READ_WRITE:
comb.append(field.r.eq(field.storage))
if field.access_dev == WRITE_ONLY or field.access_dev == READ_WRITE:
sync.append(If(field.we, field.storage.eq(field.w)))
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return Fragment(comb, sync)