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hptw: replaced PreviousWalkerState with a PageType FSM

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This commit is contained in:
David Harris 2021-07-17 13:54:58 -04:00
parent 89fd653cc1
commit 3ce22a60b3
1 changed files with 16 additions and 4 deletions
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20
wally-pipelined/src/mmu/pagetablewalker.sv
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@ -80,6 +80,7 @@ module pagetablewalker
logic ValidPTE, ADPageFault, MegapageMisaligned, TerapageMisaligned, GigapageMisaligned, BadMegapage, LeafPTE;
logic StartWalk;
logic EndWalk;
logic [1:0] NextPageType;
typedef enum {LEVEL0_SET_ADRE, LEVEL0_WDV, LEVEL0,
LEVEL1_SET_ADRE, LEVEL1_WDV, LEVEL1,
@ -87,7 +88,7 @@ module pagetablewalker
LEVEL3_SET_ADRE, LEVEL3_WDV, LEVEL3,
LEAF, IDLE, FAULT} statetype;
statetype WalkerState, NextWalkerState, PreviousWalkerState, InitialWalkerState;
statetype WalkerState, NextWalkerState, InitialWalkerState;
logic PRegEn;
logic SelDataTranslation;
@ -105,7 +106,7 @@ module pagetablewalker
flop #(`XLEN) HPTWPAdrMReg(clk, HPTWPAdrE, HPTWPAdrM);
flopenrc #(1) TLBMissMReg(clk, reset, EndWalk, StartWalk | EndWalk, DTLBMissM, DTLBMissMQ);
flopenl #(.TYPE(statetype)) WalkerStateReg(clk, reset, 1'b1, NextWalkerState, IDLE, WalkerState);
flopenl #(.TYPE(statetype)) PreviousWalkerStateReg(clk, reset, 1'b1, WalkerState, IDLE, PreviousWalkerState);
// flopenl #(.TYPE(statetype)) PreviousWalkerStateReg(clk, reset, 1'b1, WalkerState, IDLE, PreviousWalkerState);
flopenr #(`XLEN) PTEReg(clk, reset, PRegEn, HPTWReadPTE, CurrentPTE); // Capture page table entry from data cache
assign CurrentPPN = CurrentPTE[`PPN_BITS+9:10];
@ -131,17 +132,28 @@ module pagetablewalker
assign WalkerLoadPageFaultM = (WalkerState == FAULT) & DTLBMissMQ & ~MemWrite;
assign WalkerStorePageFaultM = (WalkerState == FAULT) & DTLBMissMQ & MemWrite;
always_comb // determine type of page being walked:
/* always_comb // determine type of page being walked:
case (PreviousWalkerState)
LEVEL3: PageType = 2'b11; // terapage
LEVEL2: PageType = 2'b10; // gigapage
LEVEL1: PageType = 2'b01; // megapage
default: PageType = 2'b00; // kilopage
endcase
endcase*/
assign PRegEn = (NextWalkerState == LEVEL3) | (NextWalkerState == LEVEL2) | (NextWalkerState == LEVEL1) | (NextWalkerState == LEVEL0);
assign HPTWRead = (WalkerState == LEVEL3_WDV) | (WalkerState == LEVEL2_WDV) | (WalkerState == LEVEL1_WDV) | (WalkerState == LEVEL0_WDV);
// *** is there a way to speed up HPTW?
// FSM to track PageType based on the levels of the page table traversed
flopr #(2) PageTypeReg(clk, reset, NextPageType, PageType);
always_comb
case (WalkerState)
LEVEL3: NextPageType = 2'b11; // terapage
LEVEL2: NextPageType = 2'b10; // gigapage
LEVEL1: NextPageType = 2'b01; // megapage
LEVEL0: NextPageType = 2'b00; // kilopage
default: NextPageType = PageType;
endcase
// TranslationPAdr mux
if (`XLEN==32) begin
logic [9:0] VPN1, VPN0;