108 lines
4.3 KiB
Python
108 lines
4.3 KiB
Python
from typing import TYPE_CHECKING, List
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from ..forloop_generator import RDLForLoopGenerator, LoopBody
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if TYPE_CHECKING:
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from ..exporter import RegblockExporter
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from systemrdl.node import RegNode
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class ReadbackLoopBody(LoopBody):
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def __init__(self, dim: int, iterator: str, i_type: str) -> None:
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super().__init__(dim, iterator, i_type)
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self.n_regs = 0
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def __str__(self) -> str:
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# replace $i#sz token when stringifying
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s = super().__str__()
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token = f"${self.iterator}sz"
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s = s.replace(token, str(self.n_regs))
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return s
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class ReadbackAssignmentGenerator(RDLForLoopGenerator):
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i_type = "genvar"
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loop_body_cls = ReadbackLoopBody
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def __init__(self, exp:'RegblockExporter') -> None:
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super().__init__()
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self.exp = exp
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# The readback array collects all possible readback values into a flat
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# array. The array width is equal to the CPUIF bus width. Each entry in
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# the array represents an aligned read access.
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self.current_offset = 0
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self.start_offset_stack = [] # type: List[int]
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self.dim_stack = [] # type: List[int]
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@property
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def current_offset_str(self) -> str:
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"""
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Derive a string that represents the current offset being assigned.
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This consists of:
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- The current integer offset
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- multiplied index of any enclosing loop
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The integer offset from "current_offset" is static and is monotonically
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incremented as more register assignments are processed.
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The component of the offset from loops is added by multiplying the current
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loop index by the loop size.
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Since the loop's size is not known at this time, it is emitted as a
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placeholder token like: $i0sz, $i1sz, $i2sz, etc
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These tokens can be replaced once the loop body has been completed and the
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size of its contents is known.
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"""
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offset_parts = []
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for i in range(self._loop_level):
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offset_parts.append(f"i{i}*$i{i}sz")
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offset_parts.append(str(self.current_offset))
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return " + ".join(offset_parts)
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def enter_Reg(self, node: 'RegNode') -> None:
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# TODO: account for smaller regs that are not aligned to the bus width
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# - offset the field bit slice as appropriate
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# - do not always increment the current offset
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if node.has_sw_readable:
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current_bit = 0
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rd_strb = f"({self.exp.dereferencer.get_access_strobe(node)} && !decoded_req_is_wr)"
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# Fields are sorted by ascending low bit
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for field in node.fields():
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if field.is_sw_readable:
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# insert reserved assignment before if needed
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if field.low != current_bit:
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self.add_content(f"assign readback_array[{self.current_offset_str}][{field.low-1}:{current_bit}] = '0;")
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if field.msb < field.lsb:
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# Field gets bitswapped since it is in [low:high] orientation
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value = f"{{<<{{{self.exp.dereferencer.get_value(field)}}}}}"
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else:
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value = self.exp.dereferencer.get_value(field)
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self.add_content(f"assign readback_array[{self.current_offset_str}][{field.high}:{field.low}] = {rd_strb} ? {value} : '0;")
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current_bit = field.high + 1
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# Insert final reserved assignment if needed
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bus_width = self.exp.cpuif.data_width
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if current_bit < bus_width:
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self.add_content(f"assign readback_array[{self.current_offset_str}][{bus_width-1}:{current_bit}] = '0;")
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self.current_offset += 1
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def push_loop(self, dim: int) -> None:
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super().push_loop(dim)
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self.start_offset_stack.append(self.current_offset)
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self.dim_stack.append(dim)
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def pop_loop(self) -> None:
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start_offset = self.start_offset_stack.pop()
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dim = self.dim_stack.pop()
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# Number of registers enclosed in this loop
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n_regs = self.current_offset - start_offset
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self.current_loop.n_regs = n_regs # type: ignore
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super().pop_loop()
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# Advance current scope's offset to account for loop's contents
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self.current_offset = start_offset + n_regs * dim
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