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Revert "This is a better solution. It's closer to the original book HPTW FSM,"

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This actually adds to the critical path and it's more complex than I feel comfortable.

This reverts commit 1ded4a972f.
This commit is contained in:
Rose Thompson 2024-10-11 17:02:51 -05:00
parent 1ded4a972f
commit 5011084d40
2 changed files with 376 additions and 378 deletions
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13
src/mmu/hptw.sv
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@ -153,9 +153,7 @@ module hptw import cvw::*; #(parameter cvw_t P) (
assign ValidPTE = Valid & ~(Writable & ~Readable);
assign ValidLeafPTE = ValidPTE & LeafPTE;
assign ValidNonLeafPTE = Valid & ~LeafPTE;
// assign PBMTFaultM = ValidNonLeafPTE & (|PTE[62:61]); // This is delayed one cycle so use ReadDataM instead
// It's ok for critical path because PBMTFaultM is only used to enable registers and as input to the FSM.
if(P.XLEN == 64) assign PBMTFaultM = ReadDataM[0] & ~(ReadDataM[3] | ReadDataM[2] | ReadDataM[1]) & (|ReadDataM[62:61]) & HPTWRW[1] & ~DCacheBusStallM;
if(P.XLEN == 64) assign PBMTFaultM = ValidNonLeafPTE & (|PTE[62:61]);
else assign PBMTFaultM = 1'b0;
if(P.SVADU_SUPPORTED) begin : hptwwrites
@ -280,17 +278,20 @@ module hptw import cvw::*; #(parameter cvw_t P) (
L3_RD: if (HPTWFaultM) NextWalkerState = FAULT;
else if (DCacheBusStallM) NextWalkerState = L3_RD;
else NextWalkerState = L2_ADR;
L2_ADR: if (InitialWalkerState == L2_ADR | ValidNonLeafPTE) NextWalkerState = L2_RD; // First access in SV39
L2_ADR: if (HPTWFaultM) NextWalkerState = FAULT;
else if (InitialWalkerState == L2_ADR | ValidNonLeafPTE) NextWalkerState = L2_RD; // First access in SV39
else NextWalkerState = LEAF;
L2_RD: if (HPTWFaultM) NextWalkerState = FAULT;
else if (DCacheBusStallM) NextWalkerState = L2_RD;
else NextWalkerState = L1_ADR;
L1_ADR: if (InitialWalkerState == L1_ADR | ValidNonLeafPTE) NextWalkerState = L1_RD; // First access in SV32
L1_ADR: if (HPTWFaultM) NextWalkerState = FAULT;
else if (InitialWalkerState == L1_ADR | ValidNonLeafPTE) NextWalkerState = L1_RD; // First access in SV32
else NextWalkerState = LEAF;
L1_RD: if (HPTWFaultM) NextWalkerState = FAULT;
else if (DCacheBusStallM) NextWalkerState = L1_RD;
else NextWalkerState = L0_ADR;
L0_ADR: if (ValidNonLeafPTE) NextWalkerState = L0_RD;
L0_ADR: if (HPTWFaultM) NextWalkerState = FAULT;
else if (ValidNonLeafPTE) NextWalkerState = L0_RD;
else NextWalkerState = LEAF;
L0_RD: if (HPTWFaultM) NextWalkerState = FAULT;
else if (DCacheBusStallM) NextWalkerState = L0_RD;