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hptw: FSM simplification

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This commit is contained in:
David Harris 2021-07-17 11:41:43 -04:00
parent 6d28f3fe08
commit 36a8d23222
1 changed files with 35 additions and 41 deletions
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76
wally-pipelined/src/mmu/pagetablewalker.sv
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@ -206,12 +206,10 @@ module pagetablewalker
assign TerapageMisaligned = |(CurrentPPN[26:0]); // must have zero PPN2, PPN1, PPN0 assign TerapageMisaligned = |(CurrentPPN[26:0]); // must have zero PPN2, PPN1, PPN0
assign GigapageMisaligned = |(CurrentPPN[17:0]); // must have zero PPN1 and PPN0 assign GigapageMisaligned = |(CurrentPPN[17:0]); // must have zero PPN1 and PPN0
assign MegapageMisaligned = |(CurrentPPN[8:0]); // must have zero PPN0 assign MegapageMisaligned = |(CurrentPPN[8:0]); // must have zero PPN0
end assign HPTWPAdrE = {{(`XLEN-`PA_BITS){1'b0}}, TranslationPAdr[`PA_BITS-1:0]};
end
// generate // generate
if (`XLEN == 32) begin if (`XLEN == 32) begin
// A megapage is a Level 1 leaf page. This page must have zero PPN[0].
// State transition logic // State transition logic
always_comb begin always_comb begin
case (WalkerState) case (WalkerState)
@ -234,7 +232,7 @@ module pagetablewalker
LEAF: NextWalkerState = IDLE; LEAF: NextWalkerState = IDLE;
FAULT: NextWalkerState = IDLE; FAULT: NextWalkerState = IDLE;
default: begin default: begin
$error("Default state in HPTW should be unreachable") $error("Default state in HPTW should be unreachable");
NextWalkerState = IDLE; // should never be reached NextWalkerState = IDLE; // should never be reached
end end
endcase endcase
@ -248,47 +246,43 @@ module pagetablewalker
always_comb begin always_comb begin
case (WalkerState) case (WalkerState)
IDLE: if (AnyTLBMissM) NextWalkerState = (SvMode == `SV48) ? LEVEL3_SET_ADRE : LEVEL2_SET_ADRE; IDLE: if (AnyTLBMissM)
else NextWalkerState = IDLE; if (`XLEN == 64) NextWalkerState = (SvMode == `SV48) ? LEVEL3_SET_ADRE : LEVEL2_SET_ADRE;
LEVEL3_SET_ADRE: NextWalkerState = LEVEL3_WDV; else NextWalkerState = LEVEL1_SET_ADRE;
LEVEL3_WDV: if (HPTWStall) NextWalkerState = LEVEL3_WDV; else NextWalkerState = IDLE;
else NextWalkerState = LEVEL3; LEVEL3_SET_ADRE: NextWalkerState = LEVEL3_WDV;
LEVEL3: LEVEL3_WDV: if (HPTWStall) NextWalkerState = LEVEL3_WDV;
if (ValidPTE && LeafPTE && ~(TerapageMisaligned || ADPageFault)) NextWalkerState = LEAF; else NextWalkerState = LEVEL3;
else if (ValidPTE && ~LeafPTE) NextWalkerState = LEVEL2_SET_ADRE; LEVEL3: if (ValidPTE && LeafPTE && ~(TerapageMisaligned || ADPageFault)) NextWalkerState = LEAF;
else NextWalkerState = FAULT; else if (ValidPTE && ~LeafPTE) NextWalkerState = LEVEL2_SET_ADRE;
LEVEL2_SET_ADRE: NextWalkerState = LEVEL2_WDV; else NextWalkerState = FAULT;
LEVEL2_WDV: if (HPTWStall) NextWalkerState = LEVEL2_WDV; LEVEL2_SET_ADRE: NextWalkerState = LEVEL2_WDV;
else NextWalkerState = LEVEL2; LEVEL2_WDV: if (HPTWStall) NextWalkerState = LEVEL2_WDV;
LEVEL2: else NextWalkerState = LEVEL2;
if (ValidPTE && LeafPTE && ~(GigapageMisaligned || ADPageFault)) NextWalkerState = LEAF; LEVEL2: if (ValidPTE && LeafPTE && ~(GigapageMisaligned || ADPageFault)) NextWalkerState = LEAF;
else if (ValidPTE && ~LeafPTE) NextWalkerState = LEVEL1_SET_ADRE; else if (ValidPTE && ~LeafPTE) NextWalkerState = LEVEL1_SET_ADRE;
else NextWalkerState = FAULT; else NextWalkerState = FAULT;
LEVEL1_SET_ADRE: NextWalkerState = LEVEL1_WDV; LEVEL1_SET_ADRE: NextWalkerState = LEVEL1_WDV;
LEVEL1_WDV: if (HPTWStall) NextWalkerState = LEVEL1_WDV; LEVEL1_WDV: if (HPTWStall) NextWalkerState = LEVEL1_WDV;
else NextWalkerState = LEVEL1; else NextWalkerState = LEVEL1;
LEVEL1: LEVEL1: if (ValidPTE && LeafPTE && ~(MegapageMisaligned || ADPageFault)) NextWalkerState = LEAF;
if (ValidPTE && LeafPTE && ~(MegapageMisaligned || ADPageFault)) NextWalkerState = LEAF; else if (ValidPTE && ~LeafPTE) NextWalkerState = LEVEL0_SET_ADRE;
else if (ValidPTE && ~LeafPTE) NextWalkerState = LEVEL0_SET_ADRE; else NextWalkerState = FAULT;
else NextWalkerState = FAULT; LEVEL0_SET_ADRE: NextWalkerState = LEVEL0_WDV;
LEVEL0_SET_ADRE: NextWalkerState = LEVEL0_WDV; LEVEL0_WDV: if (HPTWStall) NextWalkerState = LEVEL0_WDV;
LEVEL0_WDV: else NextWalkerState = LEVEL0;
if (HPTWStall) NextWalkerState = LEVEL0_WDV; LEVEL0: if (ValidPTE && LeafPTE && ~ADPageFault) NextWalkerState = LEAF;
else NextWalkerState = LEVEL0; else NextWalkerState = FAULT;
LEVEL0: LEAF: NextWalkerState = IDLE;
if (ValidPTE && LeafPTE && ~ADPageFault) NextWalkerState = LEAF; FAULT: NextWalkerState = IDLE;
else NextWalkerState = FAULT;
LEAF: NextWalkerState = IDLE;
FAULT: NextWalkerState = IDLE;
default: begin default: begin
$error("Default state in HPTW should be unreachable") $error("Default state in HPTW should be unreachable");
NextWalkerState = IDLE; // should never be reached NextWalkerState = IDLE; // should never be reached
end end
endcase endcase
end end
assign HPTWPAdrE = {{(`XLEN-`PA_BITS){1'b0}}, TranslationPAdr[`PA_BITS-1:0]}; end
end
end else begin end else begin
assign HPTWPAdrE = 0; assign HPTWPAdrE = 0;
assign HPTWRead = 0; assign HPTWRead = 0;