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Finished moving data path logic from the ICacheCntrl.sv to icache.sv.

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Ross Thompson 2021-08-26 13:00:21 -05:00
parent b3849d8abb
commit b230d4daec
2 changed files with 130 additions and 160 deletions
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172
wally-pipelined/src/cache/ICacheCntrl.sv vendored
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@ -28,45 +28,38 @@
module ICacheCntrl #(parameter BLOCKLEN = 256)
(
// Inputs from pipeline
input logic clk, reset,
input logic StallF, StallD,
input logic FlushD,
input logic clk, reset,
// Input the address to read
// The upper bits of the physical pc
input logic [`PA_BITS-1:0] PCNextF,
input logic [`PA_BITS-1:0] PCPF,
// Signals to/from cache memory
// The read coming out of it
input logic [31:0] ICacheMemReadData,
input logic ICacheMemReadValid,
// The address at which we want to search the cache memory
output logic [`PA_BITS-1:0] PCTagF,
output logic [`PA_BITS-1:0] PCNextIndexF,
output logic ICacheReadEn,
// inputs from mmu
input logic ITLBMissF,
input logic ITLBWriteF,
input logic WalkerInstrPageFaultF,
// BUS interface
input logic InstrAckF,
// icache internal inputs
input logic hit,
input logic FetchCountFlag,
input logic spill,
// icache internal outputs
output logic ICacheReadEn,
// Load data into the cache
output logic ICacheMemWriteEnable,
output logic [BLOCKLEN-1:0] ICacheMemWriteData,
// The instruction that was requested
// If this instruction is compressed, upper 16 bits may be the next 16 bits or may be zeros
output logic ICacheMemWriteEnable,
// Outputs to pipeline control stuff
output logic ICacheStallF, EndFetchState,
input logic ITLBMissF,
input logic ITLBWriteF,
input logic WalkerInstrPageFaultF,
output logic ICacheStallF,
// Signals to/from ahblite interface
// A read containing the requested data
input logic [`XLEN-1:0] InstrInF,
input logic InstrAckF,
// The read we request from main memory
output logic [`PA_BITS-1:0] InstrPAdrF,
output logic InstrReadF,
// Bus interface outputs
output logic InstrReadF,
output logic spill,
output logic spillSave
// icache internal outputs
output logic spillSave,
output logic CntEn,
output logic CntReset,
output logic [1:0] PCMux,
output logic SavePC
);
// FSM states
@ -114,80 +107,15 @@ module ICacheCntrl #(parameter BLOCKLEN = 256)
STATE_TLB_MISS_DONE
} statetype;
localparam AHBByteLength = `XLEN / 8;
localparam AHBOFFETWIDTH = $clog2(AHBByteLength);
localparam BlockByteLength = BLOCKLEN / 8;
localparam OFFSETWIDTH = $clog2(BlockByteLength);
localparam WORDSPERLINE = BLOCKLEN/`XLEN;
localparam LOGWPL = $clog2(WORDSPERLINE);
localparam integer PA_WIDTH = `PA_BITS - 2;
statetype CurrState, NextState;
logic hit;
logic SavePC;
logic [1:0] PCMux;
logic CntReset;
logic PreCntEn, CntEn;
logic PreCntEn;
logic UnalignedSelect;
logic FetchCountFlag;
localparam FetchCountThreshold = WORDSPERLINE - 1;
logic [LOGWPL-1:0] FetchCount, NextFetchCount;
logic [`PA_BITS-1:0] PCPreFinalF, PCPSpillF;
logic [`PA_BITS-1:OFFSETWIDTH] PCPTrunkF;
localparam [31:0] NOP = 32'h13;
logic [1:0] PCMux_q;
// Misaligned signals
//logic [`XLEN:0] MisalignedInstrRawF;
//logic MisalignedStall;
// Cache fault signals
//logic FaultStall;
// on spill we want to get the first 2 bytes of the next cache block.
// the spill only occurs if the PCPF mod BlockByteLength == -2. Therefore we can
// simply add 2 to land on the next cache block.
assign PCPSpillF = PCPF + {{{PA_WIDTH}{1'b0}}, 2'b10}; // *** modelsim does not allow the use of PA_BITS for literal width.
// now we have to select between these three PCs
assign PCPreFinalF = PCMux[0] | StallF ? PCPF : PCNextF; // *** don't like the stallf, but it is necessary
assign PCNextIndexF = PCMux[1] ? PCPSpillF : PCPreFinalF;
// this mux needs to be delayed 1 cycle as it occurs 1 pipeline stage later.
// *** read enable may not be necessary.
flopenr #(2) PCMuxReg(.clk(clk),
.reset(reset),
.en(ICacheReadEn),
.d(PCMux),
.q(PCMux_q));
assign PCTagF = PCMux_q[1] ? PCPSpillF : PCPF;
// truncate the offset from PCPF for memory address generation
assign PCPTrunkF = PCTagF[`PA_BITS-1:OFFSETWIDTH];
// the FSM is always runing, do not stall.
always_ff @(posedge clk, posedge reset)
if (reset) CurrState <= #1 STATE_READY;
else CurrState <= #1 NextState;
assign spill = PCPF[4:1] == 4'b1111 ? 1'b1 : 1'b0;
assign hit = ICacheMemReadValid; // note ICacheMemReadValid is hit.
assign FetchCountFlag = (FetchCount == FetchCountThreshold[LOGWPL-1:0]);
// Next state logic
always_comb begin
UnalignedSelect = 1'b0;
@ -385,50 +313,4 @@ module ICacheCntrl #(parameter BLOCKLEN = 256)
(CurrState == STATE_MISS_SPILL_FETCH_WDV) ||
(CurrState == STATE_MISS_SPILL_MISS_FETCH_WDV);
// to compute the fetch address we need to add the bit shifted
// counter output to the address.
flopenr #(LOGWPL)
FetchCountReg(.clk(clk),
.reset(reset | CntReset),
.en(CntEn),
.d(NextFetchCount),
.q(FetchCount));
assign NextFetchCount = FetchCount + 1'b1;
// This part is confusing.
// *** Ross Thompson reduce the complexity. This is just dumb.
// we need to remove the offset bits (PCPTrunkF). Because the AHB interface is XLEN wide
// we need to address on that number of bits so the PC is extended to the right by AHBByteLength with zeros.
// fetch count is already aligned to AHBByteLength, but we need to extend back to the full address width with
// more zeros after the addition. This will be the number of offset bits less the AHBByteLength.
logic [`PA_BITS-1:OFFSETWIDTH-LOGWPL] PCPTrunkExtF, InstrPAdrTrunkF ;
assign PCPTrunkExtF = {PCPTrunkF, {{LOGWPL}{1'b0}}};
// verilator lint_off WIDTH
assign InstrPAdrTrunkF = PCPTrunkExtF + FetchCount;
// verilator lint_on WIDTH
//assign InstrPAdrF = {{PCPTrunkF, {{LOGWPL}{1'b0}}} + FetchCount, {{OFFSETWIDTH-LOGWPL}{1'b0}}};
assign InstrPAdrF = {InstrPAdrTrunkF, {{OFFSETWIDTH-LOGWPL}{1'b0}}};
// store read data from memory interface before writing into SRAM.
genvar i;
generate
for (i = 0; i < WORDSPERLINE; i++) begin:storebuffer
flopenr #(`XLEN) sb(.clk(clk),
.reset(reset),
.en(InstrAckF & (i == FetchCount)),
.d(InstrInF),
.q(ICacheMemWriteData[(i+1)*`XLEN-1:i*`XLEN]));
end
endgenerate
// what address is used to write the SRAM?
endmodule

118
wally-pipelined/src/cache/icache.sv vendored
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@ -56,11 +56,20 @@ module icache
localparam integer BLOCKLEN = `ICACHE_BLOCKLENINBITS;
localparam integer NUMLINES = `ICACHE_WAYSIZEINBYTES*8/`ICACHE_BLOCKLENINBITS;
localparam WORDSPERLINE = BLOCKLEN/`XLEN;
localparam LOGWPL = $clog2(WORDSPERLINE);
localparam FetchCountThreshold = WORDSPERLINE - 1;
localparam BlockByteLength = BLOCKLEN / 8;
localparam OFFSETWIDTH = $clog2(BlockByteLength);
localparam integer PA_WIDTH = `PA_BITS - 2;
// Input signals to cache memory
logic FlushMem;
logic ICacheMemWriteEnable;
logic [BLOCKLEN-1:0] ICacheMemWriteData;
logic EndFetchState;
logic [`PA_BITS-1:0] PCTagF, PCNextIndexF;
// Output signals from cache memory
logic [31:0] ICacheMemReadData;
@ -73,6 +82,22 @@ module icache
logic spill;
logic spillSave;
logic FetchCountFlag;
logic CntEn;
logic [1:0] PCMux_q;
logic [LOGWPL-1:0] FetchCount, NextFetchCount;
logic [`PA_BITS-1:0] PCPreFinalF, PCPSpillF;
logic [`PA_BITS-1:OFFSETWIDTH] PCPTrunkF;
logic CntReset;
logic [1:0] PCMux;
logic SavePC;
ICacheMem #(.BLOCKLEN(BLOCKLEN), .NUMLINES(NUMLINES))
cachemem(.clk,
@ -125,32 +150,95 @@ module icache
assign CompressedF = FinalInstrRawF[1:0] != 2'b11;
assign spill = PCPF[4:1] == 4'b1111 ? 1'b1 : 1'b0;
assign hit = ICacheMemReadValid; // note ICacheMemReadValid is hit.
assign FetchCountFlag = (FetchCount == FetchCountThreshold[LOGWPL-1:0]);
// to compute the fetch address we need to add the bit shifted
// counter output to the address.
flopenr #(LOGWPL)
FetchCountReg(.clk(clk),
.reset(reset | CntReset),
.en(CntEn),
.d(NextFetchCount),
.q(FetchCount));
assign NextFetchCount = FetchCount + 1'b1;
// This part is confusing.
// *** Ross Thompson reduce the complexity. This is just dumb.
// we need to remove the offset bits (PCPTrunkF). Because the AHB interface is XLEN wide
// we need to address on that number of bits so the PC is extended to the right by AHBByteLength with zeros.
// fetch count is already aligned to AHBByteLength, but we need to extend back to the full address width with
// more zeros after the addition. This will be the number of offset bits less the AHBByteLength.
logic [`PA_BITS-1:OFFSETWIDTH-LOGWPL] PCPTrunkExtF, InstrPAdrTrunkF ;
assign PCPTrunkExtF = {PCPTrunkF, {{LOGWPL}{1'b0}}};
// verilator lint_off WIDTH
assign InstrPAdrTrunkF = PCPTrunkExtF + FetchCount;
// verilator lint_on WIDTH
//assign InstrPAdrF = {{PCPTrunkF, {{LOGWPL}{1'b0}}} + FetchCount, {{OFFSETWIDTH-LOGWPL}{1'b0}}};
assign InstrPAdrF = {InstrPAdrTrunkF, {{OFFSETWIDTH-LOGWPL}{1'b0}}};
// store read data from memory interface before writing into SRAM.
genvar i;
generate
for (i = 0; i < WORDSPERLINE; i++) begin:storebuffer
flopenr #(`XLEN) sb(.clk(clk),
.reset(reset),
.en(InstrAckF & (i == FetchCount)),
.d(InstrInF),
.q(ICacheMemWriteData[(i+1)*`XLEN-1:i*`XLEN]));
end
endgenerate
// on spill we want to get the first 2 bytes of the next cache block.
// the spill only occurs if the PCPF mod BlockByteLength == -2. Therefore we can
// simply add 2 to land on the next cache block.
assign PCPSpillF = PCPF + {{{PA_WIDTH}{1'b0}}, 2'b10}; // *** modelsim does not allow the use of PA_BITS for literal width.
// now we have to select between these three PCs
assign PCPreFinalF = PCMux[0] | StallF ? PCPF : PCNextF; // *** don't like the stallf, but it is necessary
assign PCNextIndexF = PCMux[1] ? PCPSpillF : PCPreFinalF;
// this mux needs to be delayed 1 cycle as it occurs 1 pipeline stage later.
// *** read enable may not be necessary.
flopenr #(2) PCMuxReg(.clk(clk),
.reset(reset),
.en(ICacheReadEn),
.d(PCMux),
.q(PCMux_q));
assign PCTagF = PCMux_q[1] ? PCPSpillF : PCPF;
// truncate the offset from PCPF for memory address generation
assign PCPTrunkF = PCTagF[`PA_BITS-1:OFFSETWIDTH];
ICacheCntrl #(.BLOCKLEN(BLOCKLEN))
controller(.clk,
.reset,
.StallF,
.StallD,
.FlushD,
.PCNextF,
.PCPF,
.ICacheMemReadData,
.ICacheMemReadValid,
.PCTagF,
.PCNextIndexF,
.ICacheReadEn,
.ICacheMemWriteEnable,
.ICacheMemWriteData,
.ICacheStallF,
. EndFetchState,
.ITLBMissF,
.ITLBWriteF,
.WalkerInstrPageFaultF,
.InstrInF,
.InstrAckF,
.InstrPAdrF,
.InstrReadF,
.hit(ICacheMemReadValid),
.FetchCountFlag,
.spill,
.spillSave);
.spillSave,
.CntEn,
.CntReset,
.PCMux,
.SavePC
);
// For now, assume no writes to executable memory
assign FlushMem = 1'b0;