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Fixed dcache to prevent latches in FPGA synthesized design.

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This commit is contained in:
Ross Thompson 2021-09-10 17:54:26 -05:00
parent 6f4542f063
commit 5744796431
1 changed files with 63 additions and 1 deletions
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64
wally-pipelined/src/cache/dcachefsm.sv vendored
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@ -136,6 +136,16 @@ module dcachefsm
if (reset) CurrState <= #1 STATE_READY;
else CurrState <= #1 NextState;
/* -----\/----- EXCLUDED -----\/-----
flopenl #(.TYPE(statetype))
StateReg(.clk,
.load(reset),
.en(1'b1),
.d(NextState),
.q(CurrState),
.val(STATE_READY));
-----/\----- EXCLUDED -----/\----- */
// next state logic and some state ouputs.
always_comb begin
@ -158,9 +168,23 @@ module dcachefsm
DCacheMiss = 1'b0;
LRUWriteEn = 1'b0;
MemAfterIWalkDone = 1'b0;
NextState = STATE_READY;
case (CurrState)
STATE_READY: begin
CntReset = 1'b0;
DCacheStall = 1'b0;
AHBRead = 1'b0;
AHBWrite = 1'b0;
DCacheAccess = 1'b0;
DCacheMiss = 1'b0;
SelAdrM = 2'b00;
SRAMWordWriteEnableM = 1'b0;
SetDirty = 1'b0;
LRUWriteEn = 1'b0;
CommittedM = 1'b0;
// TLB Miss
if((AnyCPUReqM & DTLBMissM) | ITLBMissF) begin
// the LSU arbiter has not yet selected the PTW.
@ -301,6 +325,9 @@ module dcachefsm
STATE_MISS_READ_WORD_DELAY: begin
//SelAdrM = 2'b10;
CommittedM = 1'b1;
SRAMWordWriteEnableM = 1'b0;
SetDirty = 1'b0;
LRUWriteEn = 1'b0;
if(&MemRWM & AtomicM[1]) begin // amo write
SelAdrM = 2'b10;
if(StallWtoDCache) begin
@ -356,6 +383,10 @@ module dcachefsm
STATE_PTW_READY: begin
// now all output connect to PTW instead of CPU.
CommittedM = 1'b1;
SelAdrM = 2'b00;
DCacheStall = 1'b0;
LRUWriteEn = 1'b0;
CntReset = 1'b0;
// In this branch we remove stall and go back to ready. There is no request for memory from the
// datapath or the walker had a fault.
@ -489,6 +520,7 @@ module dcachefsm
STATE_CPU_BUSY: begin
CommittedM = 1'b1;
SelAdrM = 2'b00;
if(StallWtoDCache) begin
NextState = STATE_CPU_BUSY;
SelAdrM = 2'b10;
@ -501,6 +533,9 @@ module dcachefsm
STATE_CPU_BUSY_FINISH_AMO: begin
CommittedM = 1'b1;
SelAdrM = 2'b10;
SRAMWordWriteEnableM = 1'b0;
SetDirty = 1'b0;
LRUWriteEn = 1'b0;
if(StallWtoDCache) begin
NextState = STATE_CPU_BUSY_FINISH_AMO;
end
@ -523,7 +558,7 @@ module dcachefsm
end
end
STATE_UNCACHED_READ : begin
STATE_UNCACHED_READ: begin
DCacheStall = 1'b1;
AHBRead = 1'b1;
CommittedM = 1'b1;
@ -536,6 +571,7 @@ module dcachefsm
STATE_UNCACHED_WRITE_DONE: begin
CommittedM = 1'b1;
SelAdrM = 2'b00;
if(StallWtoDCache) begin
NextState = STATE_CPU_BUSY;
SelAdrM = 2'b10;
@ -548,6 +584,7 @@ module dcachefsm
STATE_UNCACHED_READ_DONE: begin
CommittedM = 1'b1;
SelUncached = 1'b1;
SelAdrM = 2'b00;
if(StallWtoDCache) begin
NextState = STATE_CPU_BUSY;
SelAdrM = 2'b10;
@ -560,6 +597,21 @@ module dcachefsm
// itlb => instruction page fault states with memory request.
STATE_PTW_FAULT_READY: begin
DCacheStall = 1'b0;
DCacheAccess = 1'b0;
DCacheMiss = 1'b0;
LRUWriteEn = 1'b0;
SelAdrM = 2'b00;
MemAfterIWalkDone = 1'b0;
SetDirty = 1'b0;
LRUWriteEn = 1'b0;
CntReset = 1'b0;
AHBWrite = 1'b0;
AHBRead = 1'b0;
CommittedM = 1'b0;
NextState = STATE_READY;
// read hit valid cached
if(MemRWM[1] & CacheableM & CacheHit & ~DTLBMissM) begin
DCacheStall = 1'b0;
@ -614,6 +666,7 @@ module dcachefsm
CntReset = 1'b1;
DCacheStall = 1'b1;
AHBRead = 1'b1;
MemAfterIWalkDone = 1'b0;
end
// fault
else begin
@ -626,11 +679,13 @@ module dcachefsm
CommittedM = 1'b1;
if(StallWtoDCache) begin
NextState = STATE_PTW_FAULT_CPU_BUSY;
MemAfterIWalkDone = 1'b0;
SelAdrM = 2'b10;
end
else begin
MemAfterIWalkDone = 1'b1;
NextState = STATE_READY;
SelAdrM = 2'b00;
end
end
@ -690,10 +745,12 @@ module dcachefsm
if(StallWtoDCache) begin
NextState = STATE_PTW_FAULT_CPU_BUSY;
SelAdrM = 2'b10;
MemAfterIWalkDone = 1'b0;
end
else begin
MemAfterIWalkDone = 1'b1;
NextState = STATE_READY;
SelAdrM = 2'b00;
end
end
@ -711,11 +768,13 @@ module dcachefsm
CommittedM = 1'b1;
if(StallWtoDCache) begin
NextState = STATE_PTW_FAULT_CPU_BUSY;
MemAfterIWalkDone = 1'b0;
SelAdrM = 2'b10;
end
else begin
MemAfterIWalkDone = 1'b1;
NextState = STATE_READY;
SelAdrM = 2'b00;
end
end
@ -760,11 +819,13 @@ module dcachefsm
CommittedM = 1'b1;
if(StallWtoDCache) begin
NextState = STATE_PTW_FAULT_CPU_BUSY;
MemAfterIWalkDone = 1'b0;
SelAdrM = 2'b10;
end
else begin
MemAfterIWalkDone = 1'b1;
NextState = STATE_READY;
SelAdrM = 2'b00;
end
end
@ -782,6 +843,7 @@ module dcachefsm
end
default: begin
NextState = STATE_READY;
end
endcase
end