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tlp/common: Document.
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@enjoy-digital
enjoy-digital committed Jul 27, 2023
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221 changes: 146 additions & 75 deletions litepcie/tlp/common.py
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# Constants ----------------------------------------------------------------------------------------

# Maximum payload size and request size (in bytes).
max_payload_size = 512
max_request_size = 512

# Format (fmt) field of different types of TLPs.
fmt_dict = {
"mem_rd32": 0b00,
"mem_rd64": 0b01,
"mem_wr32": 0b10,
"mem_wr64": 0b11,
"cpld": 0b10,
"cpl": 0b00,
"cfg_rd0": 0b00,
"cfg_wr0": 0b10,
"mem_rd32": 0b00, # Memory Read Request (32-bit).
"mem_rd64": 0b01, # Memory Read Request (64-bit).
"mem_wr32": 0b10, # Memory Write Request (32-bit).
"mem_wr64": 0b11, # Memory Write Request (64-bit).
"cpld": 0b10, # Completion with Data.
"cpl": 0b00, # Completion without Data.
"cfg_rd0": 0b00, # Configuration Read Request (Type 0).
"cfg_wr0": 0b10, # Configuration Write Request (Type 0).
}

# Type (type) field of different types of TLPs.
type_dict = {
"mem_rd32": 0b00000,
"mem_rd64": 0b00000,
"mem_wr32": 0b00000,
"mem_wr64": 0b00000,
"cpld": 0b01010,
"cpl": 0b01010,
"cfg_rd0": 0b00101,
"cfg_wr0": 0b00101,
"mem_rd32": 0b00000, # Memory Read Request (32-bit).
"mem_rd64": 0b00000, # Memory Read Request (64-bit).
"mem_wr32": 0b00000, # Memory Write Request (32-bit).
"mem_wr64": 0b00000, # Memory Write Request (64-bit).
"cpld": 0b01010, # Completion with Data.
"cpl": 0b01010, # Completion without Data.
"cfg_rd0": 0b00101, # Configuration Read Request (Type 0).
"cfg_wr0": 0b00101, # Configuration Write Request (Type 0).
}

# Format and Type fields for different types of TLPs.
fmt_type_dict = {
"mem_rd32": 0b00_00000,
"mem_rd64": 0b01_00000,
"mem_wr32": 0b10_00000,
"mem_wr64": 0b11_00000,
"cpld": 0b10_01010,
"cpl": 0b00_01010,
"cfg_rd0": 0b00_00101,
"cfg_wr0": 0b10_00101,
"mem_rd32": 0b00_00000, # Memory Read Request (32-bit).
"mem_rd64": 0b01_00000, # Memory Read Request (64-bit).
"mem_wr32": 0b10_00000, # Memory Write Request (32-bit).
"mem_wr64": 0b11_00000, # Memory Write Request (64-bit).
"cpld": 0b10_01010, # Completion with Data.
"cpl": 0b00_01010, # Completion without Data.
"cfg_rd0": 0b00_00101, # Configuration Read Request (Type 0).
"cfg_wr0": 0b10_00101, # Configuration Write Request (Type 0).
}

# Completion Status (cpl) field of Completion TLPs.
cpl_dict = {
"sc": 0b000,
"ur": 0b001,
"crs": 0b010,
"ca": 0b011,
"sc": 0b000, # Successful Completion.
"ur": 0b001, # Unsupported Request.
"crs": 0b010, # Configuration Request Retry Status.
"ca": 0b011, # Completer Abort.
}

# Headers ------------------------------------------------------------------------------------------

# Length of the TLP common header (in bytes).
tlp_common_header_length = 16
# Define TLP common header fields.
tlp_common_header_fields = {
"fmt": HeaderField(byte=0*4, offset=29, width=2),
"type": HeaderField(byte=0*4, offset=24, width=5),
"fmt": HeaderField(byte=0*4, offset=29, width=2), # Format.
"type": HeaderField(byte=0*4, offset=24, width=5), # Type.
}
# Define TLP common header
tlp_common_header = Header(
fields = tlp_common_header_fields,
length = tlp_common_header_length,
swap_field_bytes = False
swap_field_bytes = False # No byte swapping required.
)

# Length of the TLP request header (in bytes).
tlp_request_header_length = 16
# Define TLP request header fields.
tlp_request_header_fields = {
"fmt": HeaderField(byte=0*4, offset=29, width= 2),
"type": HeaderField(byte=0*4, offset=24, width= 5),
"tc": HeaderField(byte=0*4, offset=20, width= 3),
"td": HeaderField(byte=0*4, offset=15, width= 1),
"ep": HeaderField(byte=0*4, offset=14, width= 1),
"attr": HeaderField(byte=0*4, offset=12, width= 2),
"length": HeaderField(byte=0*4, offset= 0, width=10),

"requester_id": HeaderField(byte=1*4, offset=16, width=16),
"tag": HeaderField(byte=1*4, offset= 8, width= 8),
"last_be": HeaderField(byte=1*4, offset= 4, width= 4),
"first_be": HeaderField(byte=1*4, offset= 0, width= 4),

"address": HeaderField(byte=2*4, offset= 0, width=64),
"fmt": HeaderField(byte=0*4, offset=29, width= 2), # Format.
"type": HeaderField(byte=0*4, offset=24, width= 5), # Type.
"tc": HeaderField(byte=0*4, offset=20, width= 3), # Traffic Class.
"td": HeaderField(byte=0*4, offset=15, width= 1), # TLP Digest.
"ep": HeaderField(byte=0*4, offset=14, width= 1), # Poisoned TLP.
"attr": HeaderField(byte=0*4, offset=12, width= 2), # Attributes.
"length": HeaderField(byte=0*4, offset= 0, width=10), # Length.

"requester_id": HeaderField(byte=1*4, offset=16, width=16), # Requester ID.
"tag": HeaderField(byte=1*4, offset= 8, width= 8), # Tag.
"last_be": HeaderField(byte=1*4, offset= 4, width= 4), # Last Byte Enable.
"first_be": HeaderField(byte=1*4, offset= 0, width= 4), # First Byte Enable.

"address": HeaderField(byte=2*4, offset= 0, width=64), # Address.
}
# Define TLP request header.
tlp_request_header = Header(
fields = tlp_request_header_fields,
length = tlp_request_header_length,
swap_field_bytes = False
swap_field_bytes = False # No byte swapping required.
)

# Length of the TLP completion header (in bytes).
tlp_completion_header_length = 16
# Define TLP completion header fields.
tlp_completion_header_fields = {
"fmt": HeaderField(byte=0*4, offset=29, width= 2),
"type": HeaderField(byte=0*4, offset=24, width= 5),
"tc": HeaderField(byte=0*4, offset=20, width= 3),
"td": HeaderField(byte=0*4, offset=15, width= 1),
"ep": HeaderField(byte=0*4, offset=14, width= 1),
"attr": HeaderField(byte=0*4, offset=12, width= 2),
"length": HeaderField(byte=0*4, offset= 0, width=10),

"completer_id": HeaderField(byte=1*4, offset=16, width=16),
"status": HeaderField(byte=1*4, offset=13, width= 3),
"bcm": HeaderField(byte=1*4, offset=12, width= 1),
"byte_count": HeaderField(byte=1*4, offset= 0, width=12),

"requester_id": HeaderField(byte=2*4, offset=16, width=16),
"tag": HeaderField(byte=2*4, offset= 8, width= 8),
"lower_address": HeaderField(byte=2*4, offset= 0, width= 7),
"fmt": HeaderField(byte=0*4, offset=29, width= 2), # Format.
"type": HeaderField(byte=0*4, offset=24, width= 5), # Type.
"tc": HeaderField(byte=0*4, offset=20, width= 3), # Traffic Class.
"td": HeaderField(byte=0*4, offset=15, width= 1), # TLP Digest.
"ep": HeaderField(byte=0*4, offset=14, width= 1), # Poisoned TLP.
"attr": HeaderField(byte=0*4, offset=12, width= 2), # Attributes.
"length": HeaderField(byte=0*4, offset= 0, width=10), # Length.

"completer_id": HeaderField(byte=1*4, offset=16, width=16), # Completer ID.
"status": HeaderField(byte=1*4, offset=13, width= 3), # Completion Status.
"bcm": HeaderField(byte=1*4, offset=12, width= 1), # Byte Count Mismatch.
"byte_count": HeaderField(byte=1*4, offset= 0, width=12), # Byte Count.

"requester_id": HeaderField(byte=2*4, offset=16, width=16), # Requester ID.
"tag": HeaderField(byte=2*4, offset= 8, width= 8), # Tag.
"lower_address": HeaderField(byte=2*4, offset= 0, width= 7), # Lower Address.
}
# Define TLP completion header.
tlp_completion_header = Header(
fields = tlp_completion_header_fields,
length = tlp_completion_header_length,
swap_field_bytes = False
swap_field_bytes = False # No byte swapping required.
)

# Helpers ------------------------------------------------------------------------------------------

def dword_endianness_swap(src, dst, data_width, endianness, mode="dat", ndwords=None):
"""
Perform an endianness swap on Migen signals.
Parameters:
src (Signal) : Source signal.
dst (Signal) : Destination signal.
data_width (int) : Width of the data (in bits).
endianness (str) : Endianness ("little" or "big").
mode (str, optional) : Mode of operation ("dat" for data or "be" for Byte Enable). Defaults to "dat".
ndwords (int, optional): Number of DWORDs. Defaults to data_width//32.
Returns:
list: List of assignments after endianness swap.
"""
# Validate inputs
assert len(src) == len(dst)
assert data_width%32 == 0
assert mode in ["dat", "be"]
r = []
# Select number of bits to swap based on the mode.
nbits = {"dat": 32, "be": 4}[mode]
# Default number of dwords to data_width//32 if not provided.
ndwords = data_width//32 if ndwords is None else ndwords
# Select reversing function based on the mode.
reverse_cls = {"dat": reverse_bytes, "be": reverse_bits}[mode]

# Iterate through each dword.
for n in range(ndwords):
low = (n + 0)*nbits
high = (n + 1)*nbits
# Add swapped dword to result list.
r += {
"little" : [dst[low:high].eq( src[low:high])],
"big" : [dst[low:high].eq(reverse_cls(src[low:high]))],
"little" : [dst[low:high].eq( src[low:high])], # If little-endian, no need for reversal.
"big" : [dst[low:high].eq(reverse_cls(src[low:high]))], # If big-endian, reverse the bytes/bits.
}[endianness]
return r

# Layouts ------------------------------------------------------------------------------------------

def tlp_raw_layout(data_width):
"""
Generate a raw TLP endpoint description.
Parameters:
data_width (int): Width of the data (in bits).
Returns:
EndpointDescription: Raw TLP endpoint description.
"""
layout = [
("fmt", 2),
("header", 4*32),
("dat", data_width),
("be", data_width//8)
("fmt", 2), # Format field.
("header", 4*32), # Header field.
("dat", data_width), # Data field.
("be", data_width//8) # Byte Enable field.
]
return EndpointDescription(layout)


def tlp_common_layout(data_width):
"""
Generate a common TLP endpoint description.
Parameters:
data_width (int): Width of the data (in bits).
Returns:
EndpointDescription: Common TLP endpoint description.
"""
layout = tlp_common_header.get_layout() + [
("dat", data_width),
("be", data_width//8)
("dat", data_width), # Data field.
("be", data_width//8) # Byte Enable field.
]
return EndpointDescription(layout)


def tlp_request_layout(data_width):
"""
Generate a request TLP endpoint description.
Parameters:
data_width (int): Width of the data (in bits).
Returns:
EndpointDescription: Request TLP endpoint description.
"""
layout = tlp_request_header.get_layout() + [
("dat", data_width),
("be", data_width//8)
("dat", data_width), # Data field.
("be", data_width//8) # Byte Enable field.
]
return EndpointDescription(layout)


def tlp_completion_layout(data_width):
"""
Generate a completion TLP endpoint description.
Parameters:
data_width (int): Width of the data (in bits).
Returns:
EndpointDescription: Completion TLP endpoint description.
"""
layout = tlp_completion_header.get_layout() + [
("dat", data_width),
("be", data_width//8)
("dat", data_width), # Data field.
("be", data_width//8) # Byte Enable field.
]
return EndpointDescription(layout)

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