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More cachefsm cleanup.

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This commit is contained in:
Ross Thompson 2022-02-07 13:19:37 -06:00
parent 708e0cf183
commit 9510a33c15
1 changed files with 39 additions and 223 deletions
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262
pipelined/src/cache/cachefsm.sv vendored
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@ -136,229 +136,45 @@ module cachefsm
if (reset) CurrState <= #1 STATE_READY;
else CurrState <= #1 NextState;
// next state logic and some state ouputs.
// *** Ross simplify: factor out next state and output logic
always_comb begin
//PreSelAdr = 2'b00;
NextState = STATE_READY;
case (CurrState)
STATE_READY: begin
//PreSelAdr = 2'b00;
// TLB Miss
if(IgnoreRequest) begin
// the LSU arbiter has not yet selected the PTW.
// The CPU needs to be stalled until that happens.
// If we set CacheStall for 1 cycle before going to
// PTW ready the CPU will stall.
// The page table walker asserts it's control 1 cycle
// after the TLBs miss.
//PreSelAdr = 2'b01;
NextState = STATE_READY;
end
// Flush dcache to next level of memory
else if(FlushCache) begin
NextState = STATE_FLUSH;
end
// amo hit
else if(Atomic[1] & (&RW) & CacheHit) begin
//PreSelAdr = 2'b01;
if(CPUBusy) begin
NextState = STATE_CPU_BUSY_FINISH_AMO;
//if (`REPLAY) PreSelAdr = 2'b01;
//else save = 1'b1;
end
else begin
NextState = STATE_READY;
end
end
// read hit valid cached
else if(RW[1] & CacheHit) begin
if(CPUBusy) begin
NextState = STATE_CPU_BUSY;
//if(`REPLAY) PreSelAdr = 2'b01;
//else save = 1'b1;
end
else begin
NextState = STATE_READY;
end
end
// write hit valid cached
else if (RW[0] & CacheHit) begin
//PreSelAdr = 2'b01;
if(CPUBusy) begin
NextState = STATE_CPU_BUSY;
//if(`REPLAY) PreSelAdr = 2'b01;
//else save = 1'b1;
end
else begin
NextState = STATE_READY;
end
end
// read or write miss valid cached
else if((|RW) & ~CacheHit) begin
NextState = STATE_MISS_FETCH_WDV;
end
else NextState = STATE_READY;
end
STATE_MISS_FETCH_WDV: begin
//PreSelAdr = 2'b01;
if (CacheBusAck) begin
NextState = STATE_MISS_FETCH_DONE;
end else begin
NextState = STATE_MISS_FETCH_WDV;
end
end
STATE_MISS_FETCH_DONE: begin
//PreSelAdr = 2'b01;
if(VictimDirty) begin
NextState = STATE_MISS_EVICT_DIRTY;
end else begin
NextState = STATE_MISS_WRITE_CACHE_LINE;
end
end
STATE_MISS_WRITE_CACHE_LINE: begin
NextState = STATE_MISS_READ_WORD;
//PreSelAdr = 2'b01;
//LRUWriteEn = 1'b1; // DO not update LRU on SRAM fetch update. Wait for subsequent read/write
end
STATE_MISS_READ_WORD: begin
//PreSelAdr = 2'b01;
if (RW[0] & ~Atomic[1]) begin // handles stores and amo write.
NextState = STATE_MISS_WRITE_WORD;
end else begin
NextState = STATE_MISS_READ_WORD_DELAY;
// delay state is required as the read signal RW[1] is still high when we
// return to the ready state because the cache is stalling the cpu.
end
end
STATE_MISS_READ_WORD_DELAY: begin
if(&RW & Atomic[1]) begin // amo write
//PreSelAdr = 2'b01;
if(CPUBusy) begin
NextState = STATE_CPU_BUSY_FINISH_AMO;
//if(~`REPLAY) save = 1'b1;
end
else begin
NextState = STATE_READY;
end
end else begin
if(CPUBusy) begin
NextState = STATE_CPU_BUSY;
//if(`REPLAY) PreSelAdr = 2'b01;
//else save = 1'b1;
end
else begin
NextState = STATE_READY;
end
end
end
STATE_MISS_WRITE_WORD: begin
//PreSelAdr = 2'b01;
if(CPUBusy) begin
NextState = STATE_CPU_BUSY;
//if(`REPLAY) PreSelAdr = 2'b01;
//else save = 1'b1;
end
else begin
NextState = STATE_READY;
end
end
STATE_MISS_EVICT_DIRTY: begin
//PreSelAdr = 2'b01;
if(CacheBusAck) begin
NextState = STATE_MISS_WRITE_CACHE_LINE;
end else begin
NextState = STATE_MISS_EVICT_DIRTY;
end
end
STATE_CPU_BUSY: begin
//PreSelAdr = 2'b00;
if(CPUBusy) begin
NextState = STATE_CPU_BUSY;
//if(`REPLAY) PreSelAdr = 2'b01;
end
else begin
NextState = STATE_READY;
end
end
STATE_CPU_BUSY_FINISH_AMO: begin
//PreSelAdr = 2'b01;
if(CPUBusy) begin
NextState = STATE_CPU_BUSY_FINISH_AMO;
end
else begin
NextState = STATE_READY;
end
end
STATE_FLUSH: begin
// intialize flush counters
//PreSelAdr = 2'b10;
NextState = STATE_FLUSH_CHECK;
end
STATE_FLUSH_CHECK: begin
//PreSelAdr = 2'b10;
if(VictimDirty) begin
NextState = STATE_FLUSH_WRITE_BACK;
end else if (FlushAdrFlag & FlushWayFlag) begin
NextState = STATE_READY;
//PreSelAdr = 2'b00;
end else if(FlushWayFlag) begin
NextState = STATE_FLUSH_INCR;
end else begin
NextState = STATE_FLUSH_CHECK;
end
end
STATE_FLUSH_INCR: begin
//PreSelAdr = 2'b10;
NextState = STATE_FLUSH_CHECK;
end
STATE_FLUSH_WRITE_BACK: begin
//PreSelAdr = 2'b10;
if(CacheBusAck) begin
NextState = STATE_FLUSH_CLEAR_DIRTY;
end else begin
NextState = STATE_FLUSH_WRITE_BACK;
end
end
STATE_FLUSH_CLEAR_DIRTY: begin
//PreSelAdr = 2'b10;
if(FlushAdrFlag & FlushWayFlag) begin
NextState = STATE_READY;
//PreSelAdr = 2'b00;
end else if (FlushWayFlag) begin
NextState = STATE_FLUSH_INCR;
end else begin
NextState = STATE_FLUSH_CHECK;
end
end
default: begin
NextState = STATE_READY;
end
STATE_READY: if(DoFlush) NextState = STATE_FLUSH;
else if(DoAMOHit & CPUBusy) NextState = STATE_CPU_BUSY_FINISH_AMO;
else if(DoReadHit & CPUBusy) NextState = STATE_CPU_BUSY;
else if (DoWriteHit & CPUBusy) NextState = STATE_CPU_BUSY;
else if(DoReadMiss | DoWriteMiss | DoAMOMiss) NextState = STATE_MISS_FETCH_WDV;
else NextState = STATE_READY;
STATE_MISS_FETCH_WDV: if (CacheBusAck) NextState = STATE_MISS_FETCH_DONE;
else NextState = STATE_MISS_FETCH_WDV;
STATE_MISS_FETCH_DONE: if(VictimDirty) NextState = STATE_MISS_EVICT_DIRTY;
else NextState = STATE_MISS_WRITE_CACHE_LINE;
STATE_MISS_WRITE_CACHE_LINE: NextState = STATE_MISS_READ_WORD;
STATE_MISS_READ_WORD: if (DoWrite & ~DoAMO) NextState = STATE_MISS_WRITE_WORD;
else NextState = STATE_MISS_READ_WORD_DELAY;
STATE_MISS_READ_WORD_DELAY: if(DoAMO & CPUBusy) NextState = STATE_CPU_BUSY_FINISH_AMO;
else if(CPUBusy) NextState = STATE_CPU_BUSY;
else NextState = STATE_READY;
STATE_MISS_WRITE_WORD: if(CPUBusy) NextState = STATE_CPU_BUSY;
else NextState = STATE_READY;
STATE_MISS_EVICT_DIRTY: if(CacheBusAck) NextState = STATE_MISS_WRITE_CACHE_LINE;
else NextState = STATE_MISS_EVICT_DIRTY;
STATE_CPU_BUSY: if(CPUBusy) NextState = STATE_CPU_BUSY;
else NextState = STATE_READY;
STATE_CPU_BUSY_FINISH_AMO: if(CPUBusy) NextState = STATE_CPU_BUSY_FINISH_AMO;
else NextState = STATE_READY;
STATE_FLUSH: NextState = STATE_FLUSH_CHECK;
STATE_FLUSH_CHECK: if(VictimDirty) NextState = STATE_FLUSH_WRITE_BACK;
else if (FlushAdrFlag & FlushWayFlag) NextState = STATE_READY;
else if(FlushWayFlag) NextState = STATE_FLUSH_INCR;
else NextState = STATE_FLUSH_CHECK;
STATE_FLUSH_INCR: NextState = STATE_FLUSH_CHECK;
STATE_FLUSH_WRITE_BACK: if(CacheBusAck) NextState = STATE_FLUSH_CLEAR_DIRTY;
else NextState = STATE_FLUSH_WRITE_BACK;
STATE_FLUSH_CLEAR_DIRTY: if(FlushAdrFlag & FlushWayFlag) NextState = STATE_READY;
else if (FlushWayFlag) NextState = STATE_FLUSH_INCR;
else NextState = STATE_FLUSH_CHECK;
default: NextState = STATE_READY;
endcase
end
@ -377,7 +193,6 @@ module cachefsm
(CurrState == STATE_FLUSH_CLEAR_DIRTY & ~(FlushAdrFlag & FlushWayFlag));
assign SetValid = CurrState == STATE_MISS_WRITE_CACHE_LINE;
assign ClearValid = '0;
// *** setdirty can probably be simplified by not caring about cpubusy
assign SetDirty = (CurrState == STATE_READY & DoAMO) |
(CurrState == STATE_READY & DoWrite) |
(CurrState == STATE_MISS_READ_WORD_DELAY & DoAMO) |
@ -388,6 +203,7 @@ module cachefsm
(CurrState == STATE_MISS_READ_WORD_DELAY & DoAMO) |
(CurrState == STATE_MISS_WRITE_WORD);
assign SRAMLineWriteEnable = (CurrState == STATE_MISS_WRITE_CACHE_LINE);
assign VDWriteEnable = (CurrState == STATE_FLUSH_CLEAR_DIRTY);
assign SelEvict = (CurrState == STATE_MISS_EVICT_DIRTY);
assign LRUWriteEn = (CurrState == STATE_READY & (DoAMOHit | DoReadHit | DoWriteHit)) |
(CurrState == STATE_MISS_READ_WORD_DELAY) |
@ -401,7 +217,6 @@ module cachefsm
(CurrState == STATE_FLUSH_CLEAR_DIRTY & ~(FlushAdrFlag & FlushWayFlag));
assign FlushAdrCntRst = (CurrState == STATE_READY & DoFlush);
assign FlushWayCntRst = (CurrState == STATE_READY & DoFlush) | (CurrState == STATE_FLUSH_INCR);
assign VDWriteEnable = (CurrState == STATE_FLUSH_CLEAR_DIRTY);
assign CacheFetchLine = (CurrState == STATE_READY & (DoAMOMiss | DoWriteMiss | DoReadMiss));
assign CacheWriteLine = (CurrState == STATE_MISS_FETCH_DONE & VictimDirty) |
(CurrState == STATE_FLUSH_CHECK & VictimDirty);
@ -409,7 +224,8 @@ module cachefsm
assign save = ((CurrState == STATE_READY & (DoAMOHit | DoReadHit | DoWriteHit) & CPUBusy) |
(CurrState == STATE_MISS_READ_WORD_DELAY & (DoAMO | DoRead) & CPUBusy) |
(CurrState == STATE_MISS_WRITE_WORD & DoWrite & CPUBusy)) & ~`REPLAY;
// **** can this be simplified?
assign PreSelAdr = ((CurrState == STATE_READY & IgnoreRequest) |
(CurrState == STATE_READY & DoAMOHit) |
(CurrState == STATE_READY & DoReadHit & (CPUBusy & `REPLAY)) |