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Refactor readback mux implementation. Improves performance (#155) and eliminates illegal streaming operator usage (#165)

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This commit is contained in:
Alex Mykyta
2025-12-10 23:17:33 -08:00
parent 4201ce975e
commit 9fc95b8769
24 changed files with 1116 additions and 634 deletions
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9
docs/architecture.rst
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@@ -38,18 +38,15 @@ This section also assigns any hardware interface outputs.
Readback
--------
The readback layer aggregates and reduces all readable registers into a single
read response. During a read operation, the same address decode strobes are used
to select the active register that is being accessed.
This allows for a simple OR-reduction operation to be used to compute the read
data response.
The readback layer aggregates and MUXes all readable registers into a single
read response.
For designs with a large number of software-readable registers, an optional
fanin re-timing stage can be enabled. This stage is automatically inserted at a
balanced point in the read-data reduction so that fanin and logic-levels are
optimally reduced.
.. figure:: diagrams/readback.png
.. figure:: diagrams/rt-readback-fanin.png
:width: 65%
:align: center

10
docs/dev_notes/Alpha-Beta Versioning
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@@ -1,10 +0,0 @@
Holy smokes this is complicated
Keep this exporter in Alpha/Beta for a while
Add some text in the readme or somewhere:
- No guarantees of correctness! This is always true with open source software,
but even more here!
Be sure to do your own validation before using this in production.
- Alpha means the implementation may change drastically!
Unlike official sem-ver, I am not making any guarantees on compatibility
- I need your help! Validating, finding edge cases, etc...

115
docs/dev_notes/template-layers/5-readback-mux
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@@ -1,35 +1,84 @@
--------------------------------------------------------------------------------
Readback mux layer
--------------------------------------------------------------------------------
Use a large always_comb block + many if statements that select the read data
based on the cpuif address.
Loops are handled the same way as address decode.
Implementation:
- Big always_comb block
- Initialize default rd_data value
- Lotsa if statements that operate on reg strb to assign rd_data
- Merges all fields together into reg
- pulls value from storage element struct, or input struct
- Provision for optional flop stage?
Other options that were considered:
- Flat case statement
con: Difficult to represent arrays. Essentially requires unrolling
con: complicates retiming strategies
con: Representing a range (required for externals) is cumbersome. Possible with stacked casez wildcards.
- AND field data with strobe, then massive OR reduce
This was the strategy prior to v1.3, but turned out to infer more overhead
than originally anticipated
- Assigning data to a flat register array, then directly indexing via address
con: Would work fine, but scales poorly for sparse regblocks.
Namely, simulators would likely allocate memory for the entire array
- Assign to a flat array that is packed sequentially, then directly indexing using a derived packed index
Concern that for sparse regfiles, the translation of addr --> packed index
becomes a nontrivial logic function
Mux Strategy:
Flat case statement:
-- Cant parameterize
+ better performance?
Pros:
- Scales well for arrays since loops can be used
- Externals work well, as address ranges can be compared
- Synthesis results show more efficient logic inference
Flat 1-hot array then OR reduce:
- Create a bus-wide flat array
eg: 32-bits x N readable registers
- Assign each element:
the readback value of each register
... masked by the register's access strobe
- I could also stuff an extra bit into the array that denotes the read is valid
A missed read will OR reduce down to a 0
- Finally, OR reduce all the elements in the array down to a flat 32-bit bus
- Retiming the large OR fanin can be done by chopping up the array into stages
for 2 stages, sqrt(N) gives each stage's fanin size. Round to favor
more fanin on 2nd stage
3 stages uses cube-root. etc...
- This has the benefit of re-using the address decode logic.
synth can choose to replicate logic if fanout is bad
Example:
logic [7:0] out;
always_comb begin
out = '0;
for(int i=0; i<64; i++) begin
if(i == addr) out = data[i];
end
end
How to implement retiming:
Ideally this would partition the design into several equal sub-regions, but
with loop structures, this is pretty difficult..
What if instead, it is partitioned into equal address ranges?
First stage compares the lower-half of the address bits.
Values are assigned to the appropriate output "bin"
logic [7:0] out[8];
always_comb begin
for(int i=0; i<8; i++) out[i] = '0;
for(int i=0; i<64; i++) begin
automatic bit [5:0] this_addr = i;
if(this_addr[2:0] == addr[2:0]) out[this_addr[5:3]] = data[i];
end
end
(not showing retiming ff for `out` and `addr`)
The second stage muxes down the resulting bins using the high address bits.
If the user up-sizes the address bits, need to check the upper bits to prevent aliasing
Assuming min address bit range is [5:0], but it was padded up to [8:0], do the following:
logic [7:0] rd_data;
always_comb begin
if(addr[8:6] != '0) begin
// Invalid read range
rd_data = '0;
end else begin
rd_data = out[addr[5:3]];
end
end
Retiming with external blocks
One minor downside is the above scheme does not work well for external blocks
that span a range of addresses. Depending on the range, it may span multiple
retiming bins which complicates how this would be assigned cleanly.
This would be complicated even further with arrays of externals since the
span of bins could change depending on the iteration.
Since externals can already be retimed, and large fanin of external blocks
is likely less of a concern, implement these as a separate readback mux on
the side that does not get retimed at all.
WARNING:
@@ -42,8 +91,14 @@ WARNING:
Forwards response strobe back up to cpu interface layer
TODO:
Dont forget about alias registers here
TODO:
Does the endinness the user sets matter anywhere?
Variables:
From decode:
decoded_addr
decoded_req
decoded_req_is_wr
Response:
readback_done
readback_err
readback_data

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pyproject.toml
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@@ -7,7 +7,7 @@ name = "peakrdl-regblock"
dynamic = ["version"]
requires-python = ">=3.7"
dependencies = [
"systemrdl-compiler ~= 1.31",
"systemrdl-compiler ~= 1.32",
"Jinja2 >= 2.11",
]

5
src/peakrdl_regblock/addr_decode.py
View File

@@ -133,8 +133,9 @@ class DecodeLogicGenerator(RDLForLoopGenerator):
self._array_stride_stack = [] # type: List[int]
def _add_addressablenode_decoding_flags(self, node: 'AddressableNode') -> None:
addr_str = self._get_address_str(node)
addr_decoding_str = f"cpuif_req_masked & (cpuif_addr >= {addr_str}) & (cpuif_addr <= {addr_str} + {SVInt(node.size - 1, self.addr_decode.exp.ds.addr_width)})"
addr_lo = self._get_address_str(node)
addr_hi = f"{addr_lo} + {SVInt(node.size - 1, self.addr_decode.exp.ds.addr_width)}"
addr_decoding_str = f"cpuif_req_masked & (cpuif_addr >= {addr_lo}) & (cpuif_addr <= {addr_hi})"
rhs = addr_decoding_str
rhs_valid_addr = addr_decoding_str
if isinstance(node, MemNode):

21
src/peakrdl_regblock/exporter.py
View File

@@ -165,12 +165,6 @@ class RegblockExporter:
# Validate that there are no unsupported constructs
DesignValidator(self).do_validate()
# Compute readback implementation early.
# Readback has the capability to disable retiming if the fanin is tiny.
# This affects the rest of the design's implementation, and must be known
# before any other templates are rendered
readback_implementation = self.readback.get_implementation()
# Build Jinja template context
context = {
"cpuif": self.cpuif,
@@ -184,7 +178,7 @@ class RegblockExporter:
"default_resetsignal_name": self.dereferencer.default_resetsignal_name,
"address_decode": self.address_decode,
"field_logic": self.field_logic,
"readback_implementation": readback_implementation,
"readback_implementation": self.readback.get_implementation(),
"ext_write_acks": ext_write_acks,
"ext_read_acks": ext_read_acks,
"parity": parity,
@@ -319,6 +313,10 @@ class DesignState:
)
self.cpuif_data_width = 32
# Also, to avoid silly edge cases, disable read fanin retiming since
# it has little benefit anyways
self.retime_read_fanin = False
#------------------------
# Min address width encloses the total size AND at least 1 useful address bit
self.addr_width = max(clog2(self.top_node.size), clog2(self.cpuif_data_width//8) + 1)
@@ -328,6 +326,15 @@ class DesignState:
msg.fatal(f"User-specified address width shall be greater than or equal to {self.addr_width}.")
self.addr_width = user_addr_width
if self.retime_read_fanin:
# Check if address width is sufficient to even bother with read fanin retiming
data_width_bytes = self.cpuif_data_width // 8
unused_low_addr_bits = clog2(data_width_bytes)
relevant_addr_width = self.addr_width - unused_low_addr_bits
if relevant_addr_width < 2:
# Unable to partition the address space. Disable retiming
self.retime_read_fanin = False
@property
def min_read_latency(self) -> int:
n = 0

63
src/peakrdl_regblock/module_tmpl.sv
View File

@@ -30,24 +30,7 @@ module {{ds.module_name}}
logic cpuif_req_masked;
{%- if ds.has_external_addressable %}
logic external_req;
logic external_pending;
logic external_wr_ack;
logic external_rd_ack;
always_ff {{get_always_ff_event(cpuif.reset)}} begin
if({{get_resetsignal(cpuif.reset)}}) begin
external_pending <= '0;
end else begin
if(external_req & ~external_wr_ack & ~external_rd_ack) external_pending <= '1;
else if(external_wr_ack | external_rd_ack) external_pending <= '0;
`ifndef SYNTHESIS
assert_bad_ext_wr_ack: assert(!external_wr_ack || (external_pending | external_req))
else $error("An external wr_ack strobe was asserted when no external request was active");
assert_bad_ext_rd_ack: assert(!external_rd_ack || (external_pending | external_req))
else $error("An external rd_ack strobe was asserted when no external request was active");
`endif
end
end
{%- endif %}
{% if ds.min_read_latency == ds.min_write_latency %}
// Read & write latencies are balanced. Stalls not required
@@ -109,11 +92,9 @@ module {{ds.module_name}}
decoded_reg_strb_t decoded_reg_strb;
logic decoded_err;
{%- if ds.has_external_addressable %}
logic decoded_strb_is_external;
logic decoded_req_is_external;
{% endif %}
{%- if ds.has_external_block %}
logic [{{cpuif.addr_width-1}}:0] decoded_addr;
{% endif %}
logic decoded_req;
logic decoded_req_is_wr;
logic [{{cpuif.data_width-1}}:0] decoded_wr_data;
@@ -147,15 +128,31 @@ module {{ds.module_name}}
decoded_err = '0;
{%- endif %}
{%- if ds.has_external_addressable %}
decoded_strb_is_external = is_external;
external_req = is_external;
decoded_req_is_external = is_external;
{%- endif %}
end
{%- if ds.has_external_addressable %}
logic external_wr_ack;
logic external_rd_ack;
always_ff {{get_always_ff_event(cpuif.reset)}} begin
if({{get_resetsignal(cpuif.reset)}}) begin
external_pending <= '0;
end else begin
if(decoded_req_is_external & ~external_wr_ack & ~external_rd_ack) external_pending <= '1;
else if(external_wr_ack | external_rd_ack) external_pending <= '0;
`ifndef SYNTHESIS
assert_bad_ext_wr_ack: assert(!external_wr_ack || (external_pending | decoded_req_is_external))
else $error("An external wr_ack strobe was asserted when no external request was active");
assert_bad_ext_rd_ack: assert(!external_rd_ack || (external_pending | decoded_req_is_external))
else $error("An external rd_ack strobe was asserted when no external request was active");
`endif
end
end
{%- endif %}
// Pass down signals to next stage
{%- if ds.has_external_block %}
assign decoded_addr = cpuif_addr;
{% endif %}
assign decoded_req = cpuif_req_masked;
assign decoded_req_is_wr = cpuif_req_is_wr;
assign decoded_wr_data = cpuif_wr_data;
@@ -223,7 +220,7 @@ module {{ds.module_name}}
{{ext_write_acks.get_implementation()|indent(8)}}
external_wr_ack = wr_ack;
end
assign cpuif_wr_ack = external_wr_ack | (decoded_req & decoded_req_is_wr & ~decoded_strb_is_external);
assign cpuif_wr_ack = external_wr_ack | (decoded_req & decoded_req_is_wr & ~decoded_req_is_external);
{%- else %}
assign cpuif_wr_ack = decoded_req & decoded_req_is_wr;
{%- endif %}
@@ -262,6 +259,22 @@ module {{ds.module_name}}
{%- endif %}
{%- endif %}
logic [{{cpuif.addr_width-1}}:0] rd_mux_addr;
{%- if ds.has_external_addressable %}
logic [{{cpuif.addr_width-1}}:0] pending_rd_addr;
// Hold read mux address to guarantee it is stable throughout any external accesses
always_ff {{get_always_ff_event(cpuif.reset)}} begin
if({{get_resetsignal(cpuif.reset)}}) begin
pending_rd_addr <= '0;
end else begin
if(decoded_req) pending_rd_addr <= decoded_addr;
end
end
assign rd_mux_addr = decoded_req ? decoded_addr : pending_rd_addr;
{%- else %}
assign rd_mux_addr = decoded_addr;
{%- endif %}
logic readback_err;
logic readback_done;
logic [{{cpuif.data_width-1}}:0] readback_data;

73
src/peakrdl_regblock/readback/__init__.py
View File

@@ -1,72 +1 @@
from typing import TYPE_CHECKING
import math
from .generators import ReadbackAssignmentGenerator
if TYPE_CHECKING:
from ..exporter import RegblockExporter, DesignState
from systemrdl.node import AddrmapNode
class Readback:
def __init__(self, exp:'RegblockExporter'):
self.exp = exp
@property
def ds(self) -> 'DesignState':
return self.exp.ds
@property
def top_node(self) -> 'AddrmapNode':
return self.exp.ds.top_node
def get_implementation(self) -> str:
gen = ReadbackAssignmentGenerator(self.exp)
array_assignments = gen.get_content(self.top_node)
array_size = gen.current_offset
# Enabling the fanin stage doesnt make sense if readback fanin is
# small. This also avoids pesky corner cases
if array_size < 4:
self.ds.retime_read_fanin = False
context = {
"array_assignments" : array_assignments,
"array_size" : array_size,
'get_always_ff_event': self.exp.dereferencer.get_always_ff_event,
'get_resetsignal': self.exp.dereferencer.get_resetsignal,
"cpuif": self.exp.cpuif,
"ds": self.ds,
}
if self.ds.retime_read_fanin:
# If adding a fanin pipeline stage, goal is to try to
# split the fanin path in the middle so that fanin into the stage
# and the following are roughly balanced.
fanin_target = math.sqrt(array_size)
# Size of fanin group to consume per fanin element
fanin_stride = math.floor(fanin_target)
# Number of array elements to reduce to.
# Round up to an extra element in case there is some residual
fanin_array_size = math.ceil(array_size / fanin_stride)
# leftovers are handled in an extra array element
fanin_residual_stride = array_size % fanin_stride
if fanin_residual_stride != 0:
# If there is a partial fanin element, reduce the number of
# loops performed in the bulk fanin stage
fanin_loop_iter = fanin_array_size - 1
else:
fanin_loop_iter = fanin_array_size
context['fanin_stride'] = fanin_stride
context['fanin_array_size'] = fanin_array_size
context['fanin_residual_stride'] = fanin_residual_stride
context['fanin_loop_iter'] = fanin_loop_iter
template = self.exp.jj_env.get_template(
"readback/templates/readback.sv"
)
return template.render(context)
from .readback import Readback

381
src/peakrdl_regblock/readback/generators.py
View File

@@ -1,381 +0,0 @@
from typing import TYPE_CHECKING, List
from systemrdl.node import RegNode, AddressableNode
from systemrdl.walker import WalkerAction
from ..forloop_generator import RDLForLoopGenerator, LoopBody
from ..utils import do_bitswap, do_slice
if TYPE_CHECKING:
from ..exporter import RegblockExporter
class ReadbackLoopBody(LoopBody):
def __init__(self, dim: int, iterator: str, i_type: str) -> None:
super().__init__(dim, iterator, i_type)
self.n_regs = 0
def __str__(self) -> str:
# replace $i#sz token when stringifying
s = super().__str__()
token = f"${self.iterator}sz"
s = s.replace(token, str(self.n_regs))
return s
class ReadbackAssignmentGenerator(RDLForLoopGenerator):
i_type = "genvar"
loop_body_cls = ReadbackLoopBody
def __init__(self, exp:'RegblockExporter') -> None:
super().__init__()
self.exp = exp
# The readback array collects all possible readback values into a flat
# array. The array width is equal to the CPUIF bus width. Each entry in
# the array represents an aligned read access.
self.current_offset = 0
self.start_offset_stack = [] # type: List[int]
self.dim_stack = [] # type: List[int]
@property
def current_offset_str(self) -> str:
"""
Derive a string that represents the current offset being assigned.
This consists of:
- The current integer offset
- multiplied index of any enclosing loop
The integer offset from "current_offset" is static and is monotonically
incremented as more register assignments are processed.
The component of the offset from loops is added by multiplying the current
loop index by the loop size.
Since the loop's size is not known at this time, it is emitted as a
placeholder token like: $i0sz, $i1sz, $i2sz, etc
These tokens can be replaced once the loop body has been completed and the
size of its contents is known.
"""
offset_parts = []
for i in range(self._loop_level):
offset_parts.append(f"i{i} * $i{i}sz")
offset_parts.append(str(self.current_offset))
return " + ".join(offset_parts)
def push_loop(self, dim: int) -> None:
super().push_loop(dim)
self.start_offset_stack.append(self.current_offset)
self.dim_stack.append(dim)
def pop_loop(self) -> None:
start_offset = self.start_offset_stack.pop()
dim = self.dim_stack.pop()
# Number of registers enclosed in this loop
n_regs = self.current_offset - start_offset
self.current_loop.n_regs = n_regs # type: ignore
super().pop_loop()
# Advance current scope's offset to account for loop's contents
self.current_offset = start_offset + n_regs * dim
def enter_AddressableComponent(self, node: 'AddressableNode') -> WalkerAction:
super().enter_AddressableComponent(node)
if node.external and not isinstance(node, RegNode):
# External block
strb = self.exp.hwif.get_external_rd_ack(node)
data = self.exp.hwif.get_external_rd_data(node)
self.add_content(f"assign readback_array[{self.current_offset_str}] = {strb} ? {data} : '0;")
self.current_offset += 1
return WalkerAction.SkipDescendants
return WalkerAction.Continue
def enter_Reg(self, node: RegNode) -> WalkerAction:
if not node.has_sw_readable:
return WalkerAction.SkipDescendants
if node.external:
self.process_external_reg(node)
return WalkerAction.SkipDescendants
accesswidth = node.get_property('accesswidth')
regwidth = node.get_property('regwidth')
rbuf = node.get_property('buffer_reads')
if rbuf:
trigger = node.get_property('rbuffer_trigger')
is_own_trigger = (isinstance(trigger, RegNode) and trigger == node)
if is_own_trigger:
if accesswidth < regwidth:
self.process_buffered_reg_with_bypass(node, regwidth, accesswidth)
else:
# bypass cancels out. Behaves like a normal reg
self.process_reg(node)
else:
self.process_buffered_reg(node, regwidth, accesswidth)
elif accesswidth < regwidth:
self.process_wide_reg(node, accesswidth)
else:
self.process_reg(node)
return WalkerAction.SkipDescendants
def process_external_reg(self, node: RegNode) -> None:
strb = self.exp.hwif.get_external_rd_ack(node)
data = self.exp.hwif.get_external_rd_data(node)
regwidth = node.get_property('regwidth')
if regwidth < self.exp.cpuif.data_width:
self.add_content(f"assign readback_array[{self.current_offset_str}][{self.exp.cpuif.data_width-1}:{regwidth}] = '0;")
self.add_content(f"assign readback_array[{self.current_offset_str}][{regwidth-1}:0] = {strb} ? {data} : '0;")
else:
self.add_content(f"assign readback_array[{self.current_offset_str}] = {strb} ? {data} : '0;")
self.current_offset += 1
def process_reg(self, node: RegNode) -> None:
current_bit = 0
rd_strb = f"({self.exp.dereferencer.get_access_strobe(node)} && !decoded_req_is_wr)"
# Fields are sorted by ascending low bit
for field in node.fields():
if not field.is_sw_readable:
continue
# insert reserved assignment before this field if needed
if field.low != current_bit:
self.add_content(f"assign readback_array[{self.current_offset_str}][{field.low-1}:{current_bit}] = '0;")
value = self.exp.dereferencer.get_value(field)
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
value = do_bitswap(value)
self.add_content(f"assign readback_array[{self.current_offset_str}][{field.high}:{field.low}] = {rd_strb} ? {value} : '0;")
current_bit = field.high + 1
# Insert final reserved assignment if needed
bus_width = self.exp.cpuif.data_width
if current_bit < bus_width:
self.add_content(f"assign readback_array[{self.current_offset_str}][{bus_width-1}:{current_bit}] = '0;")
self.current_offset += 1
def process_buffered_reg(self, node: RegNode, regwidth: int, accesswidth: int) -> None:
rbuf = self.exp.read_buffering.get_rbuf_data(node)
if accesswidth < regwidth:
# Is wide reg
n_subwords = regwidth // accesswidth
astrb = self.exp.dereferencer.get_access_strobe(node, reduce_substrobes=False)
for i in range(n_subwords):
rd_strb = f"({astrb}[{i}] && !decoded_req_is_wr)"
bslice = f"[{(i + 1) * accesswidth - 1}:{i*accesswidth}]"
self.add_content(f"assign readback_array[{self.current_offset_str}] = {rd_strb} ? {rbuf}{bslice} : '0;")
self.current_offset += 1
else:
# Is regular reg
rd_strb = f"({self.exp.dereferencer.get_access_strobe(node)} && !decoded_req_is_wr)"
self.add_content(f"assign readback_array[{self.current_offset_str}][{regwidth-1}:0] = {rd_strb} ? {rbuf} : '0;")
bus_width = self.exp.cpuif.data_width
if regwidth < bus_width:
self.add_content(f"assign readback_array[{self.current_offset_str}][{bus_width-1}:{regwidth}] = '0;")
self.current_offset += 1
def process_buffered_reg_with_bypass(self, node: RegNode, regwidth: int, accesswidth: int) -> None:
"""
Special case for a buffered register when the register is its own trigger.
First sub-word shall bypass the read buffer and assign directly.
Subsequent subwords assign from the buffer.
Caller guarantees this is a wide reg
"""
astrb = self.exp.dereferencer.get_access_strobe(node, reduce_substrobes=False)
# Generate assignments for first sub-word
bidx = 0
rd_strb = f"({astrb}[0] && !decoded_req_is_wr)"
for field in node.fields():
if not field.is_sw_readable:
continue
if field.low >= accesswidth:
# field is not in this subword.
break
if bidx < field.low:
# insert padding before
self.add_content(f"assign readback_array[{self.current_offset_str}][{field.low - 1}:{bidx}] = '0;")
if field.high >= accesswidth:
# field gets truncated
r_low = field.low
r_high = accesswidth - 1
f_low = 0
f_high = accesswidth - 1 - field.low
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
# Mirror the low/high indexes
f_low = field.width - 1 - f_low
f_high = field.width - 1 - f_high
f_low, f_high = f_high, f_low
value = do_bitswap(do_slice(self.exp.dereferencer.get_value(field), f_high, f_low))
else:
value = do_slice(self.exp.dereferencer.get_value(field), f_high, f_low)
self.add_content(f"assign readback_array[{self.current_offset_str}][{r_high}:{r_low}] = {rd_strb} ? {value} : '0;")
bidx = accesswidth
else:
# field fits in subword
value = self.exp.dereferencer.get_value(field)
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
value = do_bitswap(value)
self.add_content(f"assign readback_array[{self.current_offset_str}][{field.high}:{field.low}] = {rd_strb} ? {value} : '0;")
bidx = field.high + 1
# pad up remainder of subword
if bidx < accesswidth:
self.add_content(f"assign readback_array[{self.current_offset_str}][{accesswidth-1}:{bidx}] = '0;")
self.current_offset += 1
# Assign remainder of subwords from read buffer
n_subwords = regwidth // accesswidth
rbuf = self.exp.read_buffering.get_rbuf_data(node)
for i in range(1, n_subwords):
rd_strb = f"({astrb}[{i}] && !decoded_req_is_wr)"
bslice = f"[{(i + 1) * accesswidth - 1}:{i*accesswidth}]"
self.add_content(f"assign readback_array[{self.current_offset_str}] = {rd_strb} ? {rbuf}{bslice} : '0;")
self.current_offset += 1
def process_wide_reg(self, node: RegNode, accesswidth: int) -> None:
bus_width = self.exp.cpuif.data_width
subword_idx = 0
current_bit = 0 # Bit-offset within the wide register
access_strb = self.exp.dereferencer.get_access_strobe(node, reduce_substrobes=False)
# Fields are sorted by ascending low bit
for field in node.fields():
if not field.is_sw_readable:
continue
# insert zero assignment before this field if needed
if field.low >= accesswidth*(subword_idx+1):
# field does not start in this subword
if current_bit > accesswidth * subword_idx:
# current subword had content. Assign remainder
low = current_bit % accesswidth
high = bus_width - 1
self.add_content(f"assign readback_array[{self.current_offset_str}][{high}:{low}] = '0;")
self.current_offset += 1
# Advance to subword that contains the start of the field
subword_idx = field.low // accesswidth
current_bit = accesswidth * subword_idx
if current_bit != field.low:
# assign zero up to start of this field
low = current_bit % accesswidth
high = (field.low % accesswidth) - 1
self.add_content(f"assign readback_array[{self.current_offset_str}][{high}:{low}] = '0;")
current_bit = field.low
# Assign field
# loop until the entire field's assignments have been generated
field_pos = field.low
while current_bit <= field.high:
# Assign the field
rd_strb = f"({access_strb}[{subword_idx}] && !decoded_req_is_wr)"
if (field_pos == field.low) and (field.high < accesswidth*(subword_idx+1)):
# entire field fits into this subword
low = field.low - accesswidth * subword_idx
high = field.high - accesswidth * subword_idx
value = self.exp.dereferencer.get_value(field)
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
value = do_bitswap(value)
self.add_content(f"assign readback_array[{self.current_offset_str}][{high}:{low}] = {rd_strb} ? {value} : '0;")
current_bit = field.high + 1
if current_bit == accesswidth*(subword_idx+1):
# Field ends at the subword boundary
subword_idx += 1
self.current_offset += 1
elif field.high >= accesswidth*(subword_idx+1):
# only a subset of the field can fit into this subword
# high end gets truncated
# assignment slice
r_low = field_pos - accesswidth * subword_idx
r_high = accesswidth - 1
# field slice
f_low = field_pos - field.low
f_high = accesswidth * (subword_idx + 1) - 1 - field.low
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
# Mirror the low/high indexes
f_low = field.width - 1 - f_low
f_high = field.width - 1 - f_high
f_low, f_high = f_high, f_low
value = do_bitswap(do_slice(self.exp.dereferencer.get_value(field), f_high, f_low))
else:
value = do_slice(self.exp.dereferencer.get_value(field), f_high, f_low)
self.add_content(f"assign readback_array[{self.current_offset_str}][{r_high}:{r_low}] = {rd_strb} ? {value} : '0;")
# advance to the next subword
subword_idx += 1
current_bit = accesswidth * subword_idx
field_pos = current_bit
self.current_offset += 1
else:
# only a subset of the field can fit into this subword
# finish field
# assignment slice
r_low = field_pos - accesswidth * subword_idx
r_high = field.high - accesswidth * subword_idx
# field slice
f_low = field_pos - field.low
f_high = field.high - field.low
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
# Mirror the low/high indexes
f_low = field.width - 1 - f_low
f_high = field.width - 1 - f_high
f_low, f_high = f_high, f_low
value = do_bitswap(do_slice(self.exp.dereferencer.get_value(field), f_high, f_low))
else:
value = do_slice(self.exp.dereferencer.get_value(field), f_high, f_low)
self.add_content(f"assign readback_array[{self.current_offset_str}][{r_high}:{r_low}] = {rd_strb} ? {value} : '0;")
current_bit = field.high + 1
if current_bit == accesswidth*(subword_idx+1):
# Field ends at the subword boundary
subword_idx += 1
self.current_offset += 1
# insert zero assignment after the last field if needed
if current_bit > accesswidth * subword_idx:
# current subword had content. Assign remainder
low = current_bit % accesswidth
high = bus_width - 1
self.add_content(f"assign readback_array[{self.current_offset_str}][{high}:{low}] = '0;")
self.current_offset += 1

101
src/peakrdl_regblock/readback/readback.py Normal file
View File

@@ -0,0 +1,101 @@
from typing import TYPE_CHECKING
from .readback_mux_generator import ReadbackMuxGenerator, RetimedReadbackMuxGenerator, RetimedExtBlockReadbackMuxGenerator
from ..utils import clog2
if TYPE_CHECKING:
from ..exporter import RegblockExporter, DesignState
class Readback:
def __init__(self, exp:'RegblockExporter'):
self.exp = exp
@property
def ds(self) -> 'DesignState':
return self.exp.ds
def get_implementation(self) -> str:
if self.ds.retime_read_fanin:
return self.get_2stage_implementation()
else:
# No retiming
return self.get_1stage_implementation()
def get_empty_implementation(self) -> str:
"""
Readback implementation when there are no readable registers
"""
context = {
"ds": self.ds,
}
template = self.exp.jj_env.get_template(
"readback/templates/empty_readback.sv"
)
return template.render(context)
def get_1stage_implementation(self) -> str:
"""
Implements readback without any retiming
"""
gen = ReadbackMuxGenerator(self.exp)
mux_impl = gen.get_content(self.ds.top_node)
if not mux_impl:
# Design has no readable registers.
return self.get_empty_implementation()
context = {
"readback_mux": mux_impl,
"cpuif": self.exp.cpuif,
"ds": self.ds,
}
template = self.exp.jj_env.get_template(
"readback/templates/readback_no_rt.sv"
)
return template.render(context)
def get_2stage_implementation(self) -> str:
"""
Implements readback that is retimed to 2 stages
"""
# Split the decode to happen in two stages, using low address bits first
# then high address bits.
# Split in the middle of the "relevant" address bits - the ones that
# actually contribute to addressing in the regblock
unused_low_addr_bits = clog2(self.exp.cpuif.data_width_bytes)
relevant_addr_width = self.ds.addr_width - unused_low_addr_bits
low_addr_width = (relevant_addr_width // 2) + unused_low_addr_bits
high_addr_width = self.ds.addr_width - low_addr_width
mux_gen = RetimedReadbackMuxGenerator(self.exp)
mux_impl = mux_gen.get_content(self.ds.top_node)
if not mux_impl:
# Design has no readable addresses.
return self.get_empty_implementation()
if self.ds.has_external_block:
ext_mux_gen = RetimedExtBlockReadbackMuxGenerator(self.exp)
ext_mux_impl = ext_mux_gen.get_content(self.ds.top_node)
else:
ext_mux_impl = None
context = {
"readback_mux": mux_impl,
"ext_block_readback_mux": ext_mux_impl,
"cpuif": self.exp.cpuif,
"ds": self.ds,
"low_addr_width": low_addr_width,
"high_addr_width": high_addr_width,
'get_always_ff_event': self.exp.dereferencer.get_always_ff_event,
'get_resetsignal': self.exp.dereferencer.get_resetsignal,
}
template = self.exp.jj_env.get_template(
"readback/templates/readback_with_rt.sv"
)
return template.render(context)

361
src/peakrdl_regblock/readback/readback_mux_generator.py Normal file
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from typing import TYPE_CHECKING, List, Sequence, Optional
from systemrdl.node import RegNode, AddressableNode, FieldNode
from systemrdl.walker import WalkerAction
from ..forloop_generator import RDLForLoopGenerator
from ..utils import SVInt, do_bitswap, do_slice
if TYPE_CHECKING:
from ..exporter import DesignState, RegblockExporter
class ReadbackMuxGenerator(RDLForLoopGenerator):
def __init__(self, exp: 'RegblockExporter') -> None:
super().__init__()
self.exp = exp
# List of address strides for each dimension
self._array_stride_stack: List[int] = []
@property
def ds(self) -> 'DesignState':
return self.exp.ds
def enter_AddressableComponent(self, node: AddressableNode) -> Optional[WalkerAction]:
super().enter_AddressableComponent(node)
if node.array_dimensions:
assert node.array_stride is not None
# Collect strides for each array dimension
current_stride = node.array_stride
strides = []
for dim in reversed(node.array_dimensions):
strides.append(current_stride)
current_stride *= dim
strides.reverse()
self._array_stride_stack.extend(strides)
if node.external and not isinstance(node, RegNode):
# Is an external block
self.process_external_block(node)
return WalkerAction.SkipDescendants
return WalkerAction.Continue
def process_external_block(self, node: AddressableNode) -> None:
addr_lo = self._get_address_str(node)
addr_hi = f"{addr_lo} + {SVInt(node.size - 1, self.exp.ds.addr_width)}"
self.add_content(f"if((rd_mux_addr >= {addr_lo}) && (rd_mux_addr <= {addr_hi})) begin")
data = self.exp.hwif.get_external_rd_data(node)
self.add_content(f" readback_data_var = {data};")
self.add_content("end")
def enter_Reg(self, node: RegNode) -> WalkerAction:
fields = node.fields(sw_readable_only=True)
if not fields:
# Reg has no readable fields
return WalkerAction.SkipDescendants
if node.external:
self.process_external_reg(node)
return WalkerAction.SkipDescendants
accesswidth = node.get_property('accesswidth')
regwidth = node.get_property('regwidth')
rbuf = node.get_property('buffer_reads')
if rbuf:
trigger = node.get_property('rbuffer_trigger')
is_own_trigger = (isinstance(trigger, RegNode) and trigger == node)
if is_own_trigger:
if accesswidth < regwidth:
self.process_wide_buffered_reg_with_bypass(node, fields, regwidth, accesswidth)
else:
# bypass cancels out. Behaves like a normal reg
self.process_reg(node, fields)
else:
self.process_buffered_reg(node, regwidth, accesswidth)
elif accesswidth < regwidth:
self.process_wide_reg(node, fields, regwidth, accesswidth)
else:
self.process_reg(node, fields)
return WalkerAction.SkipDescendants
def _get_address_str(self, node: AddressableNode, subword_offset: int=0) -> str:
expr_width = self.ds.addr_width
a = str(SVInt(
node.raw_absolute_address - self.ds.top_node.raw_absolute_address + subword_offset,
expr_width
))
for i, stride in enumerate(self._array_stride_stack):
a += f" + ({expr_width})'(i{i}) * {SVInt(stride, expr_width)}"
return a
def get_addr_compare_conditional(self, addr: str) -> str:
return f"rd_mux_addr == {addr}"
def get_readback_data_var(self, addr: str) -> str:
return "readback_data_var"
def process_external_reg(self, node: RegNode) -> None:
accesswidth = node.get_property('accesswidth')
regwidth = node.get_property('regwidth')
data = self.exp.hwif.get_external_rd_data(node)
if regwidth > accesswidth:
# Is wide reg.
# The retiming scheme requires singular address comparisons rather than
# ranges. To support this, unroll the subwords
n_subwords = regwidth // accesswidth
subword_stride = accesswidth // 8
for subword_idx in range(n_subwords):
addr = self._get_address_str(node, subword_offset=subword_idx*subword_stride)
conditional = self.get_addr_compare_conditional(addr)
var = self.get_readback_data_var(addr)
self.add_content(f"if({conditional}) begin")
self.add_content(f" {var} = {data};")
self.add_content("end")
else:
addr = self._get_address_str(node)
conditional = self.get_addr_compare_conditional(addr)
var = self.get_readback_data_var(addr)
self.add_content(f"if({conditional}) begin")
if regwidth < self.exp.cpuif.data_width:
self.add_content(f" {var}[{regwidth-1}:0] = {data};")
else:
self.add_content(f" {var} = {data};")
self.add_content("end")
def process_reg(self, node: RegNode, fields: Sequence[FieldNode]) -> None:
"""
Process a regular register
"""
addr = self._get_address_str(node)
conditional = self.get_addr_compare_conditional(addr)
var = self.get_readback_data_var(addr)
self.add_content(f"if({conditional}) begin")
for field in fields:
value = self.exp.dereferencer.get_value(field)
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
value = do_bitswap(value)
if field.width == 1:
self.add_content(f" {var}[{field.low}] = {value};")
else:
self.add_content(f" {var}[{field.high}:{field.low}] = {value};")
self.add_content("end")
def process_buffered_reg(self, node: RegNode, regwidth: int, accesswidth: int) -> None:
"""
Process a register which is fully buffered
"""
rbuf = self.exp.read_buffering.get_rbuf_data(node)
if accesswidth < regwidth:
# Is wide reg
n_subwords = regwidth // accesswidth
subword_stride = accesswidth // 8
for subword_idx in range(n_subwords):
addr = self._get_address_str(node, subword_offset=subword_idx*subword_stride)
conditional = self.get_addr_compare_conditional(addr)
var = self.get_readback_data_var(addr)
bslice = f"[{(subword_idx + 1) * accesswidth - 1}:{subword_idx*accesswidth}]"
self.add_content(f"if({conditional}) begin")
self.add_content(f" {var} = {rbuf}{bslice};")
self.add_content("end")
else:
# Is regular reg
addr = self._get_address_str(node)
conditional = self.get_addr_compare_conditional(addr)
var = self.get_readback_data_var(addr)
self.add_content(f"if({conditional}) begin")
self.add_content(f" {var}[{regwidth-1}:0] = {rbuf};")
self.add_content("end")
def process_wide_buffered_reg_with_bypass(self, node: RegNode, fields: Sequence[FieldNode], regwidth: int, accesswidth: int) -> None:
"""
Special case for a wide buffered register where the register is its own
trigger.
First sub-word shall bypass the read buffer and assign directly.
Subsequent subwords assign from the buffer.
"""
# Generate assignments for first sub-word
subword_assignments = self.get_wide_reg_subword_assignments(node, fields, regwidth, accesswidth)
if subword_assignments[0]:
addr = self._get_address_str(node, subword_offset=0)
conditional = self.get_addr_compare_conditional(addr)
self.add_content(f"if({conditional}) begin")
for assignment in subword_assignments[0]:
self.add_content(" " + assignment)
self.add_content("end")
# Assign remainder of subwords from read buffer
n_subwords = regwidth // accesswidth
subword_stride = accesswidth // 8
rbuf = self.exp.read_buffering.get_rbuf_data(node)
for subword_idx in range(1, n_subwords):
addr = self._get_address_str(node, subword_offset=subword_idx*subword_stride)
bslice = f"[{(subword_idx + 1) * accesswidth - 1}:{subword_idx*accesswidth}]"
conditional = self.get_addr_compare_conditional(addr)
var = self.get_readback_data_var(addr)
self.add_content(f"if({conditional}) begin")
self.add_content(f" {var} = {rbuf}{bslice};")
self.add_content("end")
def get_wide_reg_subword_assignments(self, node: RegNode, fields: Sequence[FieldNode], regwidth: int, accesswidth: int) -> List[List[str]]:
"""
Get a list of assignments for each subword
Returns a 2d array where the first dimension indicates the subword index.
The next dimension is the list of assignments
"""
n_subwords = regwidth // accesswidth
subword_stride = accesswidth // 8
subword_assignments: List[List[str]] = [[] for _ in range(n_subwords)]
# Fields are sorted by ascending low bit
for field in fields:
subword_idx = field.low // accesswidth
if field.high < accesswidth * (subword_idx + 1):
# entire field fits into this subword
low = field.low - accesswidth * subword_idx
high = field.high - accesswidth * subword_idx
value = self.exp.dereferencer.get_value(field)
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
value = do_bitswap(value)
addr = self._get_address_str(node, subword_offset=subword_idx*subword_stride)
var = self.get_readback_data_var(addr)
subword_assignments[subword_idx].append(f"{var}[{high}:{low}] = {value};")
else:
# Field spans multiple sub-words
# loop through subword indexes until the entire field has been assigned
while field.high >= accesswidth * subword_idx:
# Allowable field window for this subword
subword_low = accesswidth * subword_idx
subword_high = subword_low + accesswidth - 1
# field slice (relative to reg)
f_low = max(subword_low, field.low)
f_high = min(subword_high, field.high)
# assignment slice
r_low = f_low - accesswidth * subword_idx
r_high = f_high - accesswidth * subword_idx
# Adjust to be relative to field
f_low -= field.low
f_high -= field.low
if field.msb < field.lsb:
# Field gets bitswapped since it is in [low:high] orientation
# Mirror the low/high indexes
f_low = field.width - 1 - f_low
f_high = field.width - 1 - f_high
f_low, f_high = f_high, f_low
value = do_bitswap(do_slice(self.exp.dereferencer.get_value(field), f_high, f_low))
else:
value = do_slice(self.exp.dereferencer.get_value(field), f_high, f_low)
addr = self._get_address_str(node, subword_offset=subword_idx*subword_stride)
var = self.get_readback_data_var(addr)
subword_assignments[subword_idx].append(f"{var}[{r_high}:{r_low}] = {value};")
# advance to the next subword
subword_idx += 1
return subword_assignments
def process_wide_reg(self, node: RegNode, fields: Sequence[FieldNode], regwidth: int, accesswidth: int) -> None:
"""
Process a register whose accesswidth < regwidth
"""
subword_assignments = self.get_wide_reg_subword_assignments(node, fields, regwidth, accesswidth)
# Add generated content, wrapped in the address conditional
subword_stride = accesswidth // 8
for subword_idx, assignments in enumerate(subword_assignments):
if not assignments:
continue
addr = self._get_address_str(node, subword_offset=subword_idx*subword_stride)
conditional = self.get_addr_compare_conditional(addr)
self.add_content(f"if({conditional}) begin")
for assignment in assignments:
self.add_content(" " + assignment)
self.add_content("end")
def exit_AddressableComponent(self, node: AddressableNode) -> None:
super().exit_AddressableComponent(node)
if not node.array_dimensions:
return
for _ in node.array_dimensions:
self._array_stride_stack.pop()
class RetimedReadbackMuxGenerator(ReadbackMuxGenerator):
"""
Alternate variant that is dedicated to building the 1st decode stage
"""
def process_external_block(self, node: AddressableNode) -> None:
# Do nothing. External blocks are handled in a completely separate readback mux
pass
def get_addr_compare_conditional(self, addr: str) -> str:
# In the pipelined variant, compare the low-bits of both sides
return f"ad_low(rd_mux_addr) == ad_low({addr})"
def get_readback_data_var(self, addr: str) -> str:
# In the pipelined variant, assign to the bin indexed by the high bits of addr
return f"readback_data_var[ad_hi({addr})]"
class RetimedExtBlockReadbackMuxGenerator(ReadbackMuxGenerator):
"""
When retiming is enabled, external blocks are implemented as a separate
reaback mux that is not retimed using a partitioned address.
This is because the address partitioning scheme used for individual register
addresses does not work cleanly for address ranges. (not possible to cleanly
map readback of a range to high-address data bins)
Since the non-retimed mux generator already implements external ranges,
re-use it and suppress generation of register logic.
"""
def enter_Reg(self, node: RegNode) -> WalkerAction:
return WalkerAction.SkipDescendants
def process_external_block(self, node: AddressableNode) -> None:
addr_lo = self._get_address_str(node)
addr_hi = f"{addr_lo} + {SVInt(node.size - 1, self.exp.ds.addr_width)}"
self.add_content(f"if((rd_mux_addr >= {addr_lo}) && (rd_mux_addr <= {addr_hi})) begin")
data = self.exp.hwif.get_external_rd_data(node)
self.add_content(f" readback_data_var = {data};")
self.add_content(" is_external_block_var = 1'b1;")
self.add_content("end")

7
src/peakrdl_regblock/readback/templates/empty_readback.sv Normal file
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assign readback_done = decoded_req & ~decoded_req_is_wr;
assign readback_data = '0;
{%- if ds.err_if_bad_addr or ds.err_if_bad_rw %}
assign readback_err = decoded_err;
{%- else %}
assign readback_err = '0;
{%- endif %}

94
src/peakrdl_regblock/readback/templates/readback.sv
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@@ -1,94 +0,0 @@
{% if array_assignments is not none %}
// Assign readback values to a flattened array
logic [{{cpuif.data_width-1}}:0] readback_array[{{array_size}}];
{{array_assignments}}
{%- if ds.retime_read_fanin %}
// fanin stage
logic [{{cpuif.data_width-1}}:0] readback_array_c[{{fanin_array_size}}];
for(genvar g=0; g<{{fanin_loop_iter}}; g++) begin
always_comb begin
automatic logic [{{cpuif.data_width-1}}:0] readback_data_var;
readback_data_var = '0;
for(int i=g*{{fanin_stride}}; i<((g+1)*{{fanin_stride}}); i++) readback_data_var |= readback_array[i];
readback_array_c[g] = readback_data_var;
end
end
{%- if fanin_residual_stride == 1 %}
assign readback_array_c[{{fanin_array_size-1}}] = readback_array[{{array_size-1}}];
{%- elif fanin_residual_stride > 1 %}
always_comb begin
automatic logic [{{cpuif.data_width-1}}:0] readback_data_var;
readback_data_var = '0;
for(int i={{(fanin_array_size-1) * fanin_stride}}; i<{{array_size}}; i++) readback_data_var |= readback_array[i];
readback_array_c[{{fanin_array_size-1}}] = readback_data_var;
end
{%- endif %}
logic [{{cpuif.data_width-1}}:0] readback_array_r[{{fanin_array_size}}];
logic readback_done_r;
logic readback_err_r;
always_ff {{get_always_ff_event(cpuif.reset)}} begin
if({{get_resetsignal(cpuif.reset)}}) begin
for(int i=0; i<{{fanin_array_size}}; i++) readback_array_r[i] <= '0;
readback_done_r <= '0;
readback_err_r <= '0;
end else begin
readback_array_r <= readback_array_c;
readback_err_r <= decoded_err;
{%- if ds.has_external_addressable %}
readback_done_r <= decoded_req & ~decoded_req_is_wr & ~decoded_strb_is_external;
{%- else %}
readback_done_r <= decoded_req & ~decoded_req_is_wr;
{%- endif %}
end
end
// Reduce the array
always_comb begin
automatic logic [{{cpuif.data_width-1}}:0] readback_data_var;
readback_done = readback_done_r;
{%- if ds.err_if_bad_addr or ds.err_if_bad_rw %}
readback_err = readback_err_r;
{%- else %}
readback_err = '0;
{%- endif %}
readback_data_var = '0;
for(int i=0; i<{{fanin_array_size}}; i++) readback_data_var |= readback_array_r[i];
readback_data = readback_data_var;
end
{%- else %}
// Reduce the array
always_comb begin
automatic logic [{{cpuif.data_width-1}}:0] readback_data_var;
{%- if ds.has_external_addressable %}
readback_done = decoded_req & ~decoded_req_is_wr & ~decoded_strb_is_external;
{%- else %}
readback_done = decoded_req & ~decoded_req_is_wr;
{%- endif %}
{%- if ds.err_if_bad_addr or ds.err_if_bad_rw %}
readback_err = decoded_err;
{%- else %}
readback_err = '0;
{%- endif %}
readback_data_var = '0;
for(int i=0; i<{{array_size}}; i++) readback_data_var |= readback_array[i];
readback_data = readback_data_var;
end
{%- endif %}
{%- else %}
assign readback_done = decoded_req & ~decoded_req_is_wr;
assign readback_data = '0;
{%- if ds.err_if_bad_addr or ds.err_if_bad_rw %}
assign readback_err = decoded_err;
{%- else %}
assign readback_err = '0;
{%- endif %}
{% endif %}

17
src/peakrdl_regblock/readback/templates/readback_no_rt.sv Normal file
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always_comb begin
automatic logic [{{cpuif.data_width-1}}:0] readback_data_var;
readback_data_var = '0;
{{readback_mux|indent}}
readback_data = readback_data_var;
{%- if ds.has_external_addressable %}
readback_done = decoded_req & ~decoded_req_is_wr & ~decoded_req_is_external;
{%- else %}
readback_done = decoded_req & ~decoded_req_is_wr;
{%- endif %}
{%- if ds.err_if_bad_addr or ds.err_if_bad_rw %}
readback_err = decoded_err;
{%- else %}
readback_err = '0;
{%- endif %}
end

82
src/peakrdl_regblock/readback/templates/readback_with_rt.sv Normal file
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function automatic bit [{{low_addr_width-1}}:0] ad_low(bit [{{ds.addr_width-1}}:0] addr);
return addr[{{low_addr_width-1}}:0];
endfunction
function automatic bit [{{high_addr_width-1}}:0] ad_hi(bit [{{ds.addr_width-1}}:0] addr);
return addr[{{ds.addr_width-1}}:{{low_addr_width}}];
endfunction
// readback stage 1
logic [{{cpuif.data_width-1}}:0] readback_data_rt_c[{{2 ** high_addr_width}}];
always_comb begin
automatic logic [{{cpuif.data_width-1}}:0] readback_data_var[{{2 ** high_addr_width}}];
for(int i=0; i<{{2 ** high_addr_width}}; i++) readback_data_var[i] = '0;
{{readback_mux|indent}}
readback_data_rt_c = readback_data_var;
end
logic [{{cpuif.data_width-1}}:0] readback_data_rt[{{2 ** high_addr_width}}];
logic readback_done_rt;
logic readback_err_rt;
logic [{{ds.addr_width-1}}:0] readback_addr_rt;
always_ff {{get_always_ff_event(cpuif.reset)}} begin
if({{get_resetsignal(cpuif.reset)}}) begin
for(int i=0; i<{{2 ** high_addr_width}}; i++) readback_data_rt[i] <= '0;
readback_done_rt <= '0;
readback_err_rt <= '0;
readback_addr_rt <= '0;
end else begin
readback_data_rt <= readback_data_rt_c;
readback_err_rt <= decoded_err;
{%- if ds.has_external_addressable %}
readback_done_rt <= decoded_req & ~decoded_req_is_wr & ~decoded_req_is_external;
{%- else %}
readback_done_rt <= decoded_req & ~decoded_req_is_wr;
{%- endif %}
readback_addr_rt <= rd_mux_addr;
end
end
{% if ds.has_external_block %}
logic [{{cpuif.data_width-1}}:0] readback_ext_block_data_rt_c;
logic readback_is_ext_block_c;
always_comb begin
automatic logic [{{cpuif.data_width-1}}:0] readback_data_var;
automatic logic is_external_block_var;
readback_data_var = '0;
is_external_block_var = '0;
{{ext_block_readback_mux|indent}}
readback_ext_block_data_rt_c = readback_data_var;
readback_is_ext_block_c = is_external_block_var;
end
logic [{{cpuif.data_width-1}}:0] readback_ext_block_data_rt;
logic readback_is_ext_block;
always_ff {{get_always_ff_event(cpuif.reset)}} begin
if({{get_resetsignal(cpuif.reset)}}) begin
readback_ext_block_data_rt <= '0;
readback_is_ext_block <= '0;
end else begin
readback_ext_block_data_rt <= readback_ext_block_data_rt_c;
readback_is_ext_block <= readback_is_ext_block_c;
end
end
{% endif %}
// readback stage 2
always_comb begin
{%- if ds.has_external_block %}
if(readback_is_ext_block) begin
readback_data = readback_ext_block_data_rt;
end else begin
readback_data = readback_data_rt[readback_addr_rt[{{ds.addr_width-1}}:{{low_addr_width}}]];
end
{%- else %}
readback_data = readback_data_rt[readback_addr_rt[{{ds.addr_width-1}}:{{low_addr_width}}]];
{%- endif %}
readback_done = readback_done_rt;
{%- if ds.err_if_bad_addr or ds.err_if_bad_rw %}
readback_err = readback_err_rt;
{%- else %}
readback_err = '0;
{%- endif %}
end

10
tests/README.md
View File

@@ -6,10 +6,10 @@
Testcases require an installation of the Questa simulator, and for `vlog` & `vsim`
commands to be visible via the PATH environment variable.
*Questa - Intel FPGA Starter Edition* can be downloaded for free from Intel:
* Go to https://www.intel.com/content/www/us/en/collections/products/fpga/software/downloads.html?edition=pro&q=questa&s=Relevancy
* Select latest version of Questa
* Download Questa files.
*Questa-Altera FPGA and Starter Edition* can be downloaded for free from Altera:
* Go to https://www.altera.com/downloads
* Select "Simulation Tools"
* Download Questa
* Install
* Be sure to choose "Starter Edition" for the free version.
* Create an account on https://licensing.intel.com
@@ -18,7 +18,7 @@ commands to be visible via the PATH environment variable.
* Go to https://licensing.intel.com/psg/s/sales-signup-evaluationlicenses
* Generate a free *Starter Edition* license file for Questa
* Easiest to use a *fixed* license using your NIC ID (MAC address of your network card via `ifconfig`)
* Download the license file and point the `LM_LICENSE_FILE` environment variable to the folder which contains it.
* Download the license file and point the `LM_LICENSE_FILE` environment variable to the folder which contains it. In newer versions of Questa, use the `SALT_LICENSE_SERVER` environment variable instead.
* (optional) Delete Intel libraries to save some disk space
* Delete `<install_dir>/questa_fse/intel`
* Edit `<install_dir>/questa_fse/modelsim.ini` and remove lines that reference the `intel` libraries

0
tests/test_only_external_blocks/__init__.py Normal file
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11
tests/test_only_external_blocks/regblock.rdl Normal file
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addrmap top {
mem ext_mem #(
longint SIZE = 0x100
) {
memwidth = 32;
mementries = SIZE / 4;
};
external ext_mem #(.SIZE(0x10)) mem1 @ 0x0000;
external ext_mem #(.SIZE(0x90)) mem2 @ 0x0200;
};

115
tests/test_only_external_blocks/tb_template.sv Normal file
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{% extends "lib/tb_base.sv" %}
{%- block dut_support %}
{% sv_line_anchor %}
external_block #(
.ADDR_WIDTH($clog2('h10))
) mem1_inst (
.clk(clk),
.rst(rst),
.req(hwif_out.mem1.req),
.req_is_wr(hwif_out.mem1.req_is_wr),
.addr(hwif_out.mem1.addr),
.wr_data(hwif_out.mem1.wr_data),
.wr_biten(hwif_out.mem1.wr_biten),
.rd_ack(hwif_in.mem1.rd_ack),
.rd_data(hwif_in.mem1.rd_data),
.wr_ack(hwif_in.mem1.wr_ack)
);
external_block #(
.ADDR_WIDTH($clog2('h90))
) mem2_inst (
.clk(clk),
.rst(rst),
.req(hwif_out.mem2.req),
.req_is_wr(hwif_out.mem2.req_is_wr),
.addr(hwif_out.mem2.addr),
.wr_data(hwif_out.mem2.wr_data),
.wr_biten(hwif_out.mem2.wr_biten),
.rd_ack(hwif_in.mem2.rd_ack),
.rd_data(hwif_in.mem2.rd_data),
.wr_ack(hwif_in.mem2.wr_ack)
);
{%- endblock %}
{% block seq %}
{% sv_line_anchor %}
##1;
cb.rst <= '0;
##1;
//--------------------------------------------------------------------------
// Simple read/write tests
//--------------------------------------------------------------------------
// mem1
repeat(32) begin
logic [31:0] x;
int unsigned addr;
x = $urandom();
addr = 'h0;
addr += $urandom_range(('h10 / 4) - 1) * 4;
cpuif.write(addr, x);
cpuif.assert_read(addr, x);
end
// mem2
repeat(32) begin
logic [31:0] x;
int unsigned addr;
x = $urandom();
addr = 'h200;
addr += $urandom_range(('h90 / 4) - 1) * 4;
cpuif.write(addr, x);
cpuif.assert_read(addr, x);
end
//--------------------------------------------------------------------------
// Pipelined access
//--------------------------------------------------------------------------
// init array with unique known value
for(int i=0; i<('h10 / 4); i++) begin
cpuif.write('h0 + i*4, 'h1000 + i);
end
for(int i=0; i<('h90 / 4); i++) begin
cpuif.write('h200 + i*4, 'h3000 + i);
end
// random pipelined read/writes
repeat(256) begin
fork
begin
int i;
logic [31:0] x;
int unsigned addr;
case($urandom_range(1))
0: begin
i = $urandom_range(('h10 / 4) - 1);
x = 'h1000 + i;
addr = 'h0 + i*4;
end
1: begin
i = $urandom_range(('h90 / 4) - 1);
x = 'h3000 + i;
addr = 'h200 + i*4;
end
endcase
case($urandom_range(1))
0: cpuif.write(addr, x);
1: cpuif.assert_read(addr, x);
endcase
end
join_none
end
wait fork;
{% endblock %}

29
tests/test_only_external_blocks/testcase.py Normal file
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from parameterized import parameterized_class
from ..lib.cpuifs.apb4 import APB4
from ..lib.cpuifs.axi4lite import AXI4Lite
from ..lib.cpuifs.passthrough import Passthrough
from ..lib.sim_testcase import SimTestCase
from ..lib.test_params import get_permutation_class_name, get_permutations
@parameterized_class(get_permutations({
"cpuif": [
APB4(),
Passthrough(),
],
"retime_read_fanin": [True, False],
"retime_read_response": [True, False],
"retime_external": [True, False],
}), class_name_func=get_permutation_class_name)
class Test(SimTestCase):
extra_tb_files = [
"../lib/external_reg.sv",
"../lib/external_block.sv",
]
init_hwif_in = False
clocking_hwif_in = False
timeout_clk_cycles = 30000
def test_dut(self):
self.run_test()