forked from Github_Repos/cvw
86 lines
4.0 KiB
Systemverilog
86 lines
4.0 KiB
Systemverilog
///////////////////////////////////////////
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// page_number_mixer.sv
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//
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// Written: tfleming@hmc.edu & jtorrey@hmc.edu 6 April 2021
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// Modified:
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//
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// Purpose: Takes two page numbers and replaces segments of the first page
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// number with segments from the second, based on the page type.
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//
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// A component of the Wally configurable RISC-V project.
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//
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// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
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// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy,
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// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software
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// is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
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// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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///////////////////////////////////////////
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`include "wally-config.vh"
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module page_number_mixer #(parameter BITS = 20,
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parameter HIGH_SEGMENT_BITS = 10) (
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input [BITS-1:0] PageNumber,
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input [BITS-1:0] MixPageNumber,
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input [1:0] PageType,
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output [BITS-1:0] PageNumberCombined
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);
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generate
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// *** Just checking XLEN is not enough to support sv39 AND sv48.
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if (`XLEN == 32) begin
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// The upper segment might have a different width than the lower segments.
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// For example, an sv39 PTE has 26 bits for PPN2 and 9 bits for the other
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// segments.
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localparam LOW_SEGMENT_BITS = (BITS - HIGH_SEGMENT_BITS);
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logic [HIGH_SEGMENT_BITS-1:0] Segment1, MixSegment1, Segment1Combined;
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logic [LOW_SEGMENT_BITS-1:0] Segment0, MixSegment0, Segment0Combined;
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// Unswizzle segments of the input page numbers
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assign {Segment1, Segment0} = PageNumber;
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assign {MixSegment1, MixSegment0} = MixPageNumber;
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// Pass through the high segment
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assign Segment1Combined = Segment1;
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// Either pass through or zero out segment 0
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mux2 #(LOW_SEGMENT_BITS) segment0mux(Segment0, MixSegment0, PageType[0], Segment0Combined);
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// Reswizzle segments of the combined page number
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assign PageNumberCombined = {Segment1Combined, Segment0Combined};
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end else begin
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// The upper segment might have a different width than the lower segments.
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// For example, an sv39 PTE has 26 bits for PPN2 and 9 bits for the other
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// segments.
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localparam LOW_SEGMENT_BITS = (BITS - HIGH_SEGMENT_BITS) / 2;
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logic [HIGH_SEGMENT_BITS-1:0] Segment2, MixSegment2, Segment2Combined;
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logic [LOW_SEGMENT_BITS-1:0] Segment1, MixSegment1, Segment1Combined;
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logic [LOW_SEGMENT_BITS-1:0] Segment0, MixSegment0, Segment0Combined;
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// Unswizzle segments of the input page number
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assign {Segment2, Segment1, Segment0} = PageNumber;
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assign {MixSegment2, MixSegment1, MixSegment0} = MixPageNumber;
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// Pass through the high segment
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assign Segment2Combined = Segment2;
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// Either pass through or zero out segments 1 and 0 based on the page type
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mux2 #(LOW_SEGMENT_BITS) segment1mux(Segment1, MixSegment1, PageType[1], Segment1Combined);
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mux2 #(LOW_SEGMENT_BITS) segment0mux(Segment0, MixSegment0, PageType[0], Segment0Combined);
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// Reswizzle segments of the combined page number
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assign PageNumberCombined = {Segment2Combined, Segment1Combined, Segment0Combined};
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end
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endgenerate
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endmodule
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