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opensecura / 3p / lowrisc / opentitan / e0066c59e40643f1a556a1336fbb21bc13a30a52 / . / hw / vendor / lowrisc_ibex / rtl / ibex_icache.sv
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// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0
/**
* Instruction cache
*
* Provides an instruction cache along with cache management, instruction buffering and prefetching
*/
`include "prim_assert.sv"
module ibex_icache #(
// Cache arrangement parameters
parameter int unsigned BusWidth = 32,
parameter int unsigned CacheSizeBytes = 4*1024,
parameter bit ICacheECC = 1'b0,
parameter int unsigned LineSize = 64,
parameter int unsigned NumWays = 2,
// Always make speculative bus requests in parallel with lookups
parameter bit SpecRequest = 1'b0,
// Only cache branch targets
parameter bit BranchCache = 1'b0
) (
// Clock and reset
input logic clk_i,
input logic rst_ni,
// Signal that the core would like instructions
input logic req_i,
// Set the cache's address counter
input logic branch_i,
input logic branch_spec_i,
input logic [31:0] addr_i,
// IF stage interface: Pass fetched instructions to the core
input logic ready_i,
output logic valid_o,
output logic [31:0] rdata_o,
output logic [31:0] addr_o,
output logic err_o,
output logic err_plus2_o,
// Instruction memory / interconnect interface: Fetch instruction data from memory
output logic instr_req_o,
input logic instr_gnt_i,
output logic [31:0] instr_addr_o,
input logic [BusWidth-1:0] instr_rdata_i,
input logic instr_err_i,
input logic instr_pmp_err_i,
input logic instr_rvalid_i,
// Cache status
input logic icache_enable_i,
input logic icache_inval_i,
output logic busy_o
);
// Local constants
localparam int unsigned ADDR_W = 32;
// Number of fill buffers (must be >= 2)
localparam int unsigned NUM_FB = 4;
// Request throttling threshold
localparam int unsigned FB_THRESHOLD = NUM_FB - 2;
// Derived parameters
localparam int unsigned LINE_SIZE_ECC = ICacheECC ? (LineSize + 8) : LineSize;
localparam int unsigned LINE_SIZE_BYTES = LineSize/8;
localparam int unsigned LINE_W = $clog2(LINE_SIZE_BYTES);
localparam int unsigned BUS_BYTES = BusWidth/8;
localparam int unsigned BUS_W = $clog2(BUS_BYTES);
localparam int unsigned LINE_BEATS = LINE_SIZE_BYTES / BUS_BYTES;
localparam int unsigned LINE_BEATS_W = $clog2(LINE_BEATS);
localparam int unsigned NUM_LINES = CacheSizeBytes / NumWays / LINE_SIZE_BYTES;
localparam int unsigned INDEX_W = $clog2(NUM_LINES);
localparam int unsigned INDEX_HI = INDEX_W + LINE_W - 1;
localparam int unsigned TAG_SIZE = ADDR_W - INDEX_W - LINE_W + 1; // 1 valid bit
localparam int unsigned TAG_SIZE_ECC = ICacheECC ? (TAG_SIZE + 6) : TAG_SIZE;
localparam int unsigned OUTPUT_BEATS = (BUS_BYTES / 2); // number of halfwords
// Prefetch signals
logic [ADDR_W-1:0] lookup_addr_aligned;
logic [ADDR_W-1:0] prefetch_addr_d, prefetch_addr_q;
logic prefetch_addr_en;
// Cache pipelipe IC0 signals
logic branch_suppress;
logic lookup_throttle;
logic lookup_req_ic0;
logic [ADDR_W-1:0] lookup_addr_ic0;
logic [INDEX_W-1:0] lookup_index_ic0;
logic fill_req_ic0;
logic [INDEX_W-1:0] fill_index_ic0;
logic [TAG_SIZE-1:0] fill_tag_ic0;
logic [LineSize-1:0] fill_wdata_ic0;
logic lookup_grant_ic0;
logic lookup_actual_ic0;
logic fill_grant_ic0;
logic tag_req_ic0;
logic [INDEX_W-1:0] tag_index_ic0;
logic [NumWays-1:0] tag_banks_ic0;
logic tag_write_ic0;
logic [TAG_SIZE_ECC-1:0] tag_wdata_ic0;
logic data_req_ic0;
logic [INDEX_W-1:0] data_index_ic0;
logic [NumWays-1:0] data_banks_ic0;
logic data_write_ic0;
logic [LINE_SIZE_ECC-1:0] data_wdata_ic0;
// Cache pipelipe IC1 signals
logic [TAG_SIZE_ECC-1:0] tag_rdata_ic1 [NumWays];
logic [LINE_SIZE_ECC-1:0] data_rdata_ic1 [NumWays];
logic [LINE_SIZE_ECC-1:0] hit_data_ic1;
logic lookup_valid_ic1;
logic [ADDR_W-1:INDEX_HI+1] lookup_addr_ic1;
logic [NumWays-1:0] tag_match_ic1;
logic tag_hit_ic1;
logic [NumWays-1:0] tag_invalid_ic1;
logic [NumWays-1:0] lowest_invalid_way_ic1;
logic [NumWays-1:0] round_robin_way_ic1, round_robin_way_q;
logic [NumWays-1:0] sel_way_ic1;
logic ecc_err_ic1;
logic ecc_write_req;
logic [NumWays-1:0] ecc_write_ways;
logic [INDEX_W-1:0] ecc_write_index;
// Fill buffer signals
logic gnt_or_pmp_err, gnt_not_pmp_err;
logic [$clog2(NUM_FB)-1:0] fb_fill_level;
logic fill_cache_new;
logic fill_new_alloc;
logic fill_spec_req, fill_spec_done, fill_spec_hold;
logic [NUM_FB-1:0][NUM_FB-1:0] fill_older_d, fill_older_q;
logic [NUM_FB-1:0] fill_alloc_sel, fill_alloc;
logic [NUM_FB-1:0] fill_busy_d, fill_busy_q;
logic [NUM_FB-1:0] fill_done;
logic [NUM_FB-1:0] fill_in_ic1;
logic [NUM_FB-1:0] fill_stale_d, fill_stale_q;
logic [NUM_FB-1:0] fill_cache_d, fill_cache_q;
logic [NUM_FB-1:0] fill_hit_ic1, fill_hit_d, fill_hit_q;
logic [NUM_FB-1:0][LINE_BEATS_W:0] fill_ext_cnt_d, fill_ext_cnt_q;
logic [NUM_FB-1:0] fill_ext_hold_d, fill_ext_hold_q;
logic [NUM_FB-1:0] fill_ext_done;
logic [NUM_FB-1:0][LINE_BEATS_W:0] fill_rvd_cnt_d, fill_rvd_cnt_q;
logic [NUM_FB-1:0] fill_rvd_done;
logic [NUM_FB-1:0] fill_ram_done_d, fill_ram_done_q;
logic [NUM_FB-1:0] fill_out_grant;
logic [NUM_FB-1:0][LINE_BEATS_W:0] fill_out_cnt_d, fill_out_cnt_q;
logic [NUM_FB-1:0] fill_out_done;
logic [NUM_FB-1:0] fill_ext_req, fill_rvd_exp, fill_ram_req, fill_out_req;
logic [NUM_FB-1:0] fill_data_sel, fill_data_reg, fill_data_hit, fill_data_rvd;
logic [NUM_FB-1:0][LINE_BEATS_W-1:0] fill_ext_off, fill_rvd_off;
logic [NUM_FB-1:0][LINE_BEATS_W:0] fill_rvd_beat;
logic [NUM_FB-1:0] fill_ext_arb, fill_ram_arb, fill_out_arb;
logic [NUM_FB-1:0] fill_rvd_arb;
logic [NUM_FB-1:0] fill_entry_en;
logic [NUM_FB-1:0] fill_addr_en;
logic [NUM_FB-1:0] fill_way_en;
logic [NUM_FB-1:0][LINE_BEATS-1:0] fill_data_en;
logic [NUM_FB-1:0][LINE_BEATS-1:0] fill_err_d, fill_err_q;
logic [ADDR_W-1:0] fill_addr_q [NUM_FB];
logic [NumWays-1:0] fill_way_q [NUM_FB];
logic [LineSize-1:0] fill_data_d [NUM_FB];
logic [LineSize-1:0] fill_data_q [NUM_FB];
logic [ADDR_W-1:BUS_W] fill_ext_req_addr;
logic [ADDR_W-1:0] fill_ram_req_addr;
logic [NumWays-1:0] fill_ram_req_way;
logic [LineSize-1:0] fill_ram_req_data;
logic [LineSize-1:0] fill_out_data;
logic [LINE_BEATS-1:0] fill_out_err;
// External req signals
logic instr_req;
logic [ADDR_W-1:BUS_W] instr_addr;
// Data output signals
logic skid_complete_instr;
logic skid_ready;
logic output_compressed;
logic skid_valid_d, skid_valid_q, skid_en;
logic [15:0] skid_data_d, skid_data_q;
logic skid_err_q;
logic output_valid;
logic addr_incr_two;
logic output_addr_en;
logic [ADDR_W-1:1] output_addr_d, output_addr_q;
logic [15:0] output_data_lo, output_data_hi;
logic data_valid, output_ready;
logic [LineSize-1:0] line_data;
logic [LINE_BEATS-1:0] line_err;
logic [31:0] line_data_muxed;
logic line_err_muxed;
logic [31:0] output_data;
logic output_err;
// Invalidations
logic start_inval, inval_done;
logic reset_inval_q;
logic inval_prog_d, inval_prog_q;
logic [INDEX_W-1:0] inval_index_d, inval_index_q;
//////////////////////////
// Instruction prefetch //
//////////////////////////
assign lookup_addr_aligned = {lookup_addr_ic0[ADDR_W-1:LINE_W],{LINE_W{1'b0}}};
// The prefetch address increments by one cache line for each granted request.
// This address is also updated if there is a branch that is not granted, since the target
// address (addr_i) is only valid for one cycle while branch_i is high.
// The captured branch target address is not forced to be aligned since the offset in the cache
// line must also be recorded for later use by the fill buffers.
assign prefetch_addr_d =
lookup_grant_ic0 ? (lookup_addr_aligned + {{ADDR_W-LINE_W-1{1'b0}},1'b1,{LINE_W{1'b0}}}) :
addr_i;
assign prefetch_addr_en = branch_i | lookup_grant_ic0;
always_ff @(posedge clk_i) begin
if (prefetch_addr_en) begin
prefetch_addr_q <= prefetch_addr_d;
end
end
////////////////////////
// Pipeline stage IC0 //
////////////////////////
// Cache lookup
assign lookup_throttle = (fb_fill_level > FB_THRESHOLD[$clog2(NUM_FB)-1:0]);
assign lookup_req_ic0 = req_i & ~&fill_busy_q & (branch_i | ~lookup_throttle) & ~ecc_write_req;
assign lookup_addr_ic0 = branch_spec_i ? addr_i :
prefetch_addr_q;
assign lookup_index_ic0 = lookup_addr_ic0[INDEX_HI:LINE_W];
// Cache write
assign fill_req_ic0 = (|fill_ram_req);
assign fill_index_ic0 = fill_ram_req_addr[INDEX_HI:LINE_W];
assign fill_tag_ic0 = {(~inval_prog_q & ~ecc_write_req),fill_ram_req_addr[ADDR_W-1:INDEX_HI+1]};
assign fill_wdata_ic0 = fill_ram_req_data;
// Suppress a new lookup on a not-taken branch (as the address will be incorrect)
assign branch_suppress = branch_spec_i & ~branch_i;
// Arbitrated signals - lookups have highest priority
assign lookup_grant_ic0 = lookup_req_ic0 & ~branch_suppress;
assign fill_grant_ic0 = fill_req_ic0 & (~lookup_req_ic0 | branch_suppress) & ~inval_prog_q &
~ecc_write_req;
// Qualified lookup grant to mask ram signals in IC1 if access was not made
assign lookup_actual_ic0 = lookup_grant_ic0 & icache_enable_i & ~inval_prog_q & ~start_inval;
// Tagram
assign tag_req_ic0 = lookup_req_ic0 | fill_req_ic0 | inval_prog_q | ecc_write_req;
assign tag_index_ic0 = inval_prog_q ? inval_index_q :
ecc_write_req ? ecc_write_index :
fill_grant_ic0 ? fill_index_ic0 :
lookup_index_ic0;
assign tag_banks_ic0 = ecc_write_req ? ecc_write_ways :
fill_grant_ic0 ? fill_ram_req_way :
{NumWays{1'b1}};
assign tag_write_ic0 = fill_grant_ic0 | inval_prog_q | ecc_write_req;
// Dataram
assign data_req_ic0 = lookup_req_ic0 | fill_req_ic0;
assign data_index_ic0 = tag_index_ic0;
assign data_banks_ic0 = tag_banks_ic0;
assign data_write_ic0 = tag_write_ic0;
// Append ECC checkbits to write data if required
if (ICacheECC) begin : gen_ecc_wdata
// Tagram ECC
// Reuse the same ecc encoding module for larger cache sizes by padding with zeros
logic [21:0] tag_ecc_input_padded;
logic [27:0] tag_ecc_output_padded;
logic [22-TAG_SIZE:0] tag_ecc_output_unused;
assign tag_ecc_input_padded = {{22-TAG_SIZE{1'b0}},fill_tag_ic0};
assign tag_ecc_output_unused = tag_ecc_output_padded[21:TAG_SIZE-1];
prim_secded_28_22_enc tag_ecc_enc (
.in (tag_ecc_input_padded),
.out (tag_ecc_output_padded)
);
assign tag_wdata_ic0 = {tag_ecc_output_padded[27:22],tag_ecc_output_padded[TAG_SIZE-1:0]};
// Dataram ECC
prim_secded_72_64_enc data_ecc_enc (
.in (fill_wdata_ic0),
.out (data_wdata_ic0)
);
end else begin : gen_noecc_wdata
assign tag_wdata_ic0 = fill_tag_ic0;
assign data_wdata_ic0 = fill_wdata_ic0;
end
////////////////
// IC0 -> IC1 //
////////////////
for (genvar way = 0; way < NumWays; way++) begin : gen_rams
// Tag RAM instantiation
prim_ram_1p #(
.Width (TAG_SIZE_ECC),
.Depth (NUM_LINES),
.DataBitsPerMask (TAG_SIZE_ECC)
) tag_bank (
.clk_i (clk_i),
.req_i (tag_req_ic0 & tag_banks_ic0[way]),
.write_i (tag_write_ic0),
.wmask_i ({TAG_SIZE_ECC{1'b1}}),
.addr_i (tag_index_ic0),
.wdata_i (tag_wdata_ic0),
.rdata_o (tag_rdata_ic1[way])
);
// Data RAM instantiation
prim_ram_1p #(
.Width (LINE_SIZE_ECC),
.Depth (NUM_LINES),
.DataBitsPerMask (LINE_SIZE_ECC)
) data_bank (
.clk_i (clk_i),
.req_i (data_req_ic0 & data_banks_ic0[way]),
.write_i (data_write_ic0),
.wmask_i ({LINE_SIZE_ECC{1'b1}}),
.addr_i (data_index_ic0),
.wdata_i (data_wdata_ic0),
.rdata_o (data_rdata_ic1[way])
);
end
always_ff @(posedge clk_i or negedge rst_ni) begin
if (!rst_ni) begin
lookup_valid_ic1 <= 1'b0;
end else begin
lookup_valid_ic1 <= lookup_actual_ic0;
end
end
always_ff @(posedge clk_i) begin
if (lookup_grant_ic0) begin
lookup_addr_ic1 <= lookup_addr_ic0[ADDR_W-1:INDEX_HI+1];
fill_in_ic1 <= fill_alloc_sel;
end
end
////////////////////////
// Pipeline stage IC1 //
////////////////////////
// Tag matching
for (genvar way = 0; way < NumWays; way++) begin : gen_tag_match
assign tag_match_ic1[way] = (tag_rdata_ic1[way][TAG_SIZE-1:0] ==
{1'b1,lookup_addr_ic1[ADDR_W-1:INDEX_HI+1]});
assign tag_invalid_ic1[way] = ~tag_rdata_ic1[way][TAG_SIZE-1];
end
assign tag_hit_ic1 = |tag_match_ic1;
// Hit data mux
always_comb begin
hit_data_ic1 = 'b0;
for (int way = 0; way < NumWays; way++) begin
if (tag_match_ic1[way]) begin
hit_data_ic1 |= data_rdata_ic1[way];
end
end
end
// Way selection for allocations to the cache (onehot signals)
// 1 first invalid way
// 2 global round-robin (pseudorandom) way
assign lowest_invalid_way_ic1[0] = tag_invalid_ic1[0];
assign round_robin_way_ic1[0] = round_robin_way_q[NumWays-1];
for (genvar way = 1; way < NumWays; way++) begin : gen_lowest_way
assign lowest_invalid_way_ic1[way] = tag_invalid_ic1[way] & ~|tag_invalid_ic1[way-1:0];
assign round_robin_way_ic1[way] = round_robin_way_q[way-1];
end
always_ff @(posedge clk_i or negedge rst_ni) begin
if (!rst_ni) begin
round_robin_way_q <= {{NumWays-1{1'b0}},1'b1};
end else if (lookup_valid_ic1) begin
round_robin_way_q <= round_robin_way_ic1;
end
end
assign sel_way_ic1 = |tag_invalid_ic1 ? lowest_invalid_way_ic1 :
round_robin_way_q;
// ECC checking logic
if (ICacheECC) begin : gen_data_ecc_checking
logic [NumWays-1:0] tag_err_ic1;
logic [1:0] data_err_ic1;
logic ecc_correction_write_d, ecc_correction_write_q;
logic [NumWays-1:0] ecc_correction_ways_d, ecc_correction_ways_q;
logic [INDEX_W-1:0] lookup_index_ic1, ecc_correction_index_q;
// Tag ECC checking
for (genvar way = 0; way < NumWays; way++) begin : gen_tag_ecc
logic [1:0] tag_err_bank_ic1;
logic [27:0] tag_rdata_padded_ic1;
// Expand the tag rdata with extra padding if the tag size is less than the maximum
assign tag_rdata_padded_ic1 = {tag_rdata_ic1[way][TAG_SIZE_ECC-1-:6],
{22-TAG_SIZE{1'b0}},
tag_rdata_ic1[way][TAG_SIZE-1:0]};
prim_secded_28_22_dec data_ecc_dec (
.in (tag_rdata_padded_ic1),
.d_o (),
.syndrome_o (),
.err_o (tag_err_bank_ic1)
);
assign tag_err_ic1[way] = |tag_err_bank_ic1;
end
// Data ECC checking
// Note - could generate for all ways and mux after
prim_secded_72_64_dec data_ecc_dec (
.in (hit_data_ic1),
.d_o (),
.syndrome_o (),
.err_o (data_err_ic1)
);
assign ecc_err_ic1 = lookup_valid_ic1 & ((|data_err_ic1) | (|tag_err_ic1));
// Error correction
// All ways will be invalidated on a tag error to prevent X-propagation from data_err_ic1 on
// spurious hits. Also prevents the same line being allocated twice when there was a true
// hit and a spurious hit.
assign ecc_correction_ways_d = {NumWays{|tag_err_ic1}} |
(tag_match_ic1 & {NumWays{|data_err_ic1}});
assign ecc_correction_write_d = ecc_err_ic1;
always_ff @(posedge clk_i or negedge rst_ni) begin
if (!rst_ni) begin
ecc_correction_write_q <= 1'b0;
end else begin
ecc_correction_write_q <= ecc_correction_write_d;
end
end
// The index is required in IC1 only when ECC is configured so is registered here
always_ff @(posedge clk_i) begin
if (lookup_grant_ic0) begin
lookup_index_ic1 <= lookup_addr_ic0[INDEX_HI-:INDEX_W];
end
end
// Store the ways with errors to be invalidated
always_ff @(posedge clk_i) begin
if (ecc_err_ic1) begin
ecc_correction_ways_q <= ecc_correction_ways_d;
ecc_correction_index_q <= lookup_index_ic1;
end
end
assign ecc_write_req = ecc_correction_write_q;
assign ecc_write_ways = ecc_correction_ways_q;
assign ecc_write_index = ecc_correction_index_q;
end else begin : gen_no_data_ecc
assign ecc_err_ic1 = 1'b0;
assign ecc_write_req = 1'b0;
assign ecc_write_ways = '0;
assign ecc_write_index = '0;
end
///////////////////////////////
// Cache allocation decision //
///////////////////////////////
if (BranchCache) begin : gen_caching_logic
// Cache branch target + a number of subsequent lines
localparam int unsigned CACHE_AHEAD = 2;
localparam int unsigned CACHE_CNT_W = (CACHE_AHEAD == 1) ? 1 : $clog2(CACHE_AHEAD) + 1;
logic cache_cnt_dec;
logic [CACHE_CNT_W-1:0] cache_cnt_d, cache_cnt_q;
assign cache_cnt_dec = lookup_grant_ic0 & (|cache_cnt_q);
assign cache_cnt_d = branch_i ? CACHE_AHEAD[CACHE_CNT_W-1:0] :
(cache_cnt_q - {{CACHE_CNT_W-1{1'b0}},cache_cnt_dec});
always_ff @(posedge clk_i or negedge rst_ni) begin
if (!rst_ni) begin
cache_cnt_q <= '0;
end else begin
cache_cnt_q <= cache_cnt_d;
end
end
assign fill_cache_new = (branch_i | (|cache_cnt_q)) & icache_enable_i &
~icache_inval_i & ~inval_prog_q;
end else begin : gen_cache_all
// Cache all missing fetches
assign fill_cache_new = icache_enable_i & ~start_inval & ~inval_prog_q;
end
//////////////////////////
// Fill buffer tracking //
//////////////////////////
always_comb begin
fb_fill_level = '0;
for (int i = 0; i < NUM_FB; i++) begin
if (fill_busy_q[i] & ~fill_stale_q[i]) begin
fb_fill_level += {{$clog2(NUM_FB)-1{1'b0}},1'b1};
end
end
end
// PMP errors might not / don't need to be granted (since the external request is masked)
assign gnt_or_pmp_err = instr_gnt_i | instr_pmp_err_i;
assign gnt_not_pmp_err = instr_gnt_i & ~instr_pmp_err_i;
// Allocate a new buffer for every granted lookup
assign fill_new_alloc = lookup_grant_ic0;
// Track whether a speculative external request was made from IC0, and whether it was granted
assign fill_spec_req = (SpecRequest | branch_i) & ~|fill_ext_req;
assign fill_spec_done = fill_spec_req & gnt_not_pmp_err;
assign fill_spec_hold = fill_spec_req & ~gnt_or_pmp_err;
for (genvar fb = 0; fb < NUM_FB; fb++) begin : gen_fbs
/////////////////////////////
// Fill buffer allocations //
/////////////////////////////
// Allocate the lowest available buffer
if (fb == 0) begin : gen_fb_zero
assign fill_alloc_sel[fb] = ~fill_busy_q[fb];
end else begin : gen_fb_rest
assign fill_alloc_sel[fb] = ~fill_busy_q[fb] & (&fill_busy_q[fb-1:0]);
end
assign fill_alloc[fb] = fill_alloc_sel[fb] & fill_new_alloc;
assign fill_busy_d[fb] = fill_alloc[fb] | (fill_busy_q[fb] & ~fill_done[fb]);
// Track which other fill buffers are older than this one (for age-based arbitration)
// TODO sparsify
assign fill_older_d[fb] = (fill_alloc[fb] ? fill_busy_q : fill_older_q[fb]) & ~fill_done;
// A fill buffer can release once all its actions are completed
// all data written to the cache (unless hit or error)
assign fill_done[fb] = (fill_ram_done_q[fb] | fill_hit_q[fb] | ~fill_cache_q[fb] |
(|fill_err_q[fb])) &
// all data output unless stale due to intervening branch
(fill_out_done[fb] | fill_stale_q[fb] | branch_i) &
// all external requests completed
fill_rvd_done[fb];
/////////////////////////////////
// Fill buffer status tracking //
/////////////////////////////////
// Track staleness (requests become stale when a branch intervenes)
assign fill_stale_d[fb] = fill_busy_q[fb] & (branch_i | fill_stale_q[fb]);
// Track whether or not this request should allocate to the cache
// Any invalidation or disabling of the cache while the buffer is busy will stop allocation
assign fill_cache_d[fb] = (fill_alloc[fb] & fill_cache_new) |
(fill_cache_q[fb] & fill_busy_q[fb] &
icache_enable_i & ~icache_inval_i);
// Record whether the request hit in the cache
assign fill_hit_ic1[fb] = lookup_valid_ic1 & fill_in_ic1[fb] & tag_hit_ic1 & ~ecc_err_ic1;
assign fill_hit_d[fb] = fill_hit_ic1[fb] | (fill_hit_q[fb] & fill_busy_q[fb]);
///////////////////////////////////////////
// Fill buffer external request tracking //
///////////////////////////////////////////
// Make an external request
assign fill_ext_req[fb] = fill_busy_q[fb] & ~fill_ext_done[fb];
// Count the number of completed external requests (each line requires LINE_BEATS requests)
// Don't count fake PMP error grants here since they will never receive an rvalid response
assign fill_ext_cnt_d[fb] = fill_alloc[fb] ?
{{LINE_BEATS_W{1'b0}},fill_spec_done} :
(fill_ext_cnt_q[fb] + {{LINE_BEATS_W{1'b0}},
fill_ext_arb[fb] & gnt_not_pmp_err});
// External request must be held until granted
assign fill_ext_hold_d[fb] = (fill_alloc[fb] & fill_spec_hold) |
(fill_ext_arb[fb] & ~gnt_or_pmp_err);
// External requests are completed when the counter is filled or when the request is cancelled
assign fill_ext_done[fb] = (fill_ext_cnt_q[fb][LINE_BEATS_W] |
// external requests are considered complete if the request hit
fill_hit_ic1[fb] | fill_hit_q[fb] |
// external requests will stop once any PMP error is received
fill_err_q[fb][fill_ext_off[fb]] |
// cancel if the line is stale and won't be cached
(~fill_cache_q[fb] & (branch_i | fill_stale_q[fb]))) &
// can't cancel while we are waiting for a grant on the bus
~fill_ext_hold_q[fb];
// Track whether this fill buffer expects to receive beats of data
assign fill_rvd_exp[fb] = fill_busy_q[fb] & ~fill_rvd_done[fb];
// Count the number of rvalid beats received
assign fill_rvd_cnt_d[fb] = fill_alloc[fb] ? '0 :
(fill_rvd_cnt_q[fb] +
{{LINE_BEATS_W{1'b0}},fill_rvd_arb[fb]});
// External data is complete when all issued external requests have received their data
assign fill_rvd_done[fb] = fill_ext_done[fb] & (fill_rvd_cnt_q[fb] == fill_ext_cnt_q[fb]);
//////////////////////////////////////
// Fill buffer data output tracking //
//////////////////////////////////////
// Send data to the IF stage for requests that are not stale, have not completed their
// data output, and have data available to send.
// Data is available if:
// - The request hit in the cache
// - The current beat is an error (since a PMP error might not actually receive any data)
// - Buffered data is available (fill_rvd_cnt_q is ahead of fill_out_cnt_q)
// - Data is available from the bus this cycle (fill_rvd_arb)
assign fill_out_req[fb] = fill_busy_q[fb] & ~fill_stale_q[fb] & ~fill_out_done[fb] &
(fill_hit_ic1[fb] | fill_hit_q[fb] |
(fill_err_q[fb][fill_out_cnt_q[fb][LINE_BEATS_W-1:0]]) |
(fill_rvd_beat[fb] > fill_out_cnt_q[fb]) | fill_rvd_arb[fb]);
// Calculate when a beat of data is output. Any ECC error squashes the output that cycle.
assign fill_out_grant[fb] = fill_out_arb[fb] & output_ready;
// Count the beats of data output to the IF stage
assign fill_out_cnt_d[fb] = fill_alloc[fb] ? {1'b0,lookup_addr_ic0[LINE_W-1:BUS_W]} :
(fill_out_cnt_q[fb] +
{{LINE_BEATS_W{1'b0}},fill_out_grant[fb]});
// Data output complete when the counter fills
assign fill_out_done[fb] = fill_out_cnt_q[fb][LINE_BEATS_W];
//////////////////////////////////////
// Fill buffer ram request tracking //
//////////////////////////////////////
// make a fill request once all data beats received
assign fill_ram_req[fb] = fill_busy_q[fb] & fill_rvd_cnt_q[fb][LINE_BEATS_W] &
// unless the request hit, was non-allocating or got an error
~fill_hit_q[fb] & fill_cache_q[fb] & ~|fill_err_q[fb] &
// or the request was already completed
~fill_ram_done_q[fb];
// Record when a cache allocation request has been completed
assign fill_ram_done_d[fb] = fill_ram_arb[fb] | (fill_ram_done_q[fb] & fill_busy_q[fb]);
//////////////////////////////
// Fill buffer line offsets //
//////////////////////////////
// When we branch into the middle of a line, the output count will not start from zero. This
// beat count is used to know which incoming rdata beats are relevant.
assign fill_rvd_beat[fb] = {1'b0,fill_addr_q[fb][LINE_W-1:BUS_W]} +
fill_rvd_cnt_q[fb][LINE_BEATS_W:0];
assign fill_ext_off[fb] = fill_addr_q[fb][LINE_W-1:BUS_W] +
fill_ext_cnt_q[fb][LINE_BEATS_W-1:0];
assign fill_rvd_off[fb] = fill_rvd_beat[fb][LINE_BEATS_W-1:0];
/////////////////////////////
// Fill buffer arbitration //
/////////////////////////////
// Age based arbitration - all these signals are one-hot
assign fill_ext_arb[fb] = fill_ext_req[fb] & ~|(fill_ext_req & fill_older_q[fb]);
assign fill_ram_arb[fb] = fill_ram_req[fb] & fill_grant_ic0 & ~|(fill_ram_req & fill_older_q[fb]);
// Calculate which fill buffer is the oldest one which still needs to output data to IF
assign fill_data_sel[fb] = ~|(fill_busy_q & ~fill_out_done & ~fill_stale_q &
fill_older_q[fb]);
// Arbitrate the request which has data available to send, and is the oldest outstanding
assign fill_out_arb[fb] = fill_out_req[fb] & fill_data_sel[fb];
// Assign incoming rvalid data to the oldest fill buffer expecting it
assign fill_rvd_arb[fb] = instr_rvalid_i & fill_rvd_exp[fb] & ~|(fill_rvd_exp & fill_older_q[fb]);
/////////////////////////////
// Fill buffer data muxing //
/////////////////////////////
// Output data muxing controls
// 1. Select data from the fill buffer data register
assign fill_data_reg[fb] = fill_busy_q[fb] & ~fill_stale_q[fb] &
~fill_out_done[fb] & fill_data_sel[fb] &
// The incoming data is already ahead of the output count
((fill_rvd_beat[fb] > fill_out_cnt_q[fb]) | fill_hit_q[fb] |
(|fill_err_q[fb]));
// 2. Select IC1 hit data
assign fill_data_hit[fb] = fill_busy_q[fb] & fill_hit_ic1[fb] & fill_data_sel[fb];
// 3. Select incoming instr_rdata_i
assign fill_data_rvd[fb] = fill_busy_q[fb] & fill_rvd_arb[fb] & ~fill_hit_q[fb] &
~fill_hit_ic1[fb] & ~fill_stale_q[fb] & ~fill_out_done[fb] &
// The incoming data lines up with the output count
(fill_rvd_beat[fb] == fill_out_cnt_q[fb]) & fill_data_sel[fb];
///////////////////////////
// Fill buffer registers //
///////////////////////////
// Fill buffer general enable
assign fill_entry_en[fb] = fill_alloc[fb] | fill_busy_q[fb];
always_ff @(posedge clk_i or negedge rst_ni) begin
if (!rst_ni) begin
fill_busy_q[fb] <= 1'b0;
fill_older_q[fb] <= '0;
fill_stale_q[fb] <= 1'b0;
fill_cache_q[fb] <= 1'b0;
fill_hit_q[fb] <= 1'b0;
fill_ext_cnt_q[fb] <= '0;
fill_ext_hold_q[fb] <= 1'b0;
fill_rvd_cnt_q[fb] <= '0;
fill_ram_done_q[fb] <= 1'b0;
fill_out_cnt_q[fb] <= '0;
end else if (fill_entry_en[fb]) begin
fill_busy_q[fb] <= fill_busy_d[fb];
fill_older_q[fb] <= fill_older_d[fb];
fill_stale_q[fb] <= fill_stale_d[fb];
fill_cache_q[fb] <= fill_cache_d[fb];
fill_hit_q[fb] <= fill_hit_d[fb];
fill_ext_cnt_q[fb] <= fill_ext_cnt_d[fb];
fill_ext_hold_q[fb] <= fill_ext_hold_d[fb];
fill_rvd_cnt_q[fb] <= fill_rvd_cnt_d[fb];
fill_ram_done_q[fb] <= fill_ram_done_d[fb];
fill_out_cnt_q[fb] <= fill_out_cnt_d[fb];
end
end
////////////////////////////////////////
// Fill buffer address / data storage //
////////////////////////////////////////
assign fill_addr_en[fb] = fill_alloc[fb];
assign fill_way_en[fb] = (lookup_valid_ic1 & fill_in_ic1[fb]);
always_ff @(posedge clk_i) begin
if (fill_addr_en[fb]) begin
fill_addr_q[fb] <= lookup_addr_ic0;
end
end
always_ff @(posedge clk_i) begin
if (fill_way_en[fb]) begin
fill_way_q[fb] <= sel_way_ic1;
end
end
// Data either comes from the cache or the bus. If there was an ECC error, we must take
// the incoming bus data since the cache hit data is corrupted.
assign fill_data_d[fb] = fill_hit_ic1[fb] ? hit_data_ic1[LineSize-1:0] :
{LINE_BEATS{instr_rdata_i}};
for (genvar b = 0; b < LINE_BEATS; b++) begin : gen_data_buf
// Error tracking (per beat)
// Either a PMP error on a speculative request,
assign fill_err_d[fb][b] = (instr_pmp_err_i & fill_alloc[fb] & fill_spec_req &
(lookup_addr_ic0[LINE_W-1:BUS_W] == b[LINE_BEATS_W-1:0])) |
// a PMP error on a fill buffer ext req
(instr_pmp_err_i & fill_ext_arb[fb] &
(fill_ext_off[fb] == b[LINE_BEATS_W-1:0])) |
// Or a data error with instr_rvalid_i
(fill_rvd_arb[fb] & instr_err_i &
(fill_rvd_off[fb] == b[LINE_BEATS_W-1:0])) |
// Hold the error once recorded
(fill_busy_q[fb] & fill_err_q[fb][b]);
always_ff @(posedge clk_i or negedge rst_ni) begin
if (!rst_ni) begin
fill_err_q[fb][b] <= '0;
end else if (fill_entry_en[fb]) begin
fill_err_q[fb][b] <= fill_err_d[fb][b];
end
end
// Enable the relevant part of the data register (or all for cache hits)
// Ignore incoming rvalid data when we already have cache hit data
assign fill_data_en[fb][b] = fill_hit_ic1[fb] |
(fill_rvd_arb[fb] & ~fill_hit_q[fb] &
(fill_rvd_off[fb] == b[LINE_BEATS_W-1:0]));
always_ff @(posedge clk_i) begin
if (fill_data_en[fb][b]) begin
fill_data_q[fb][b*BusWidth+:BusWidth] <= fill_data_d[fb][b*BusWidth+:BusWidth];
end
end
end
end
////////////////////////////////
// Fill buffer one-hot muxing //
////////////////////////////////
// External req info
always_comb begin
fill_ext_req_addr = '0;
for (int i = 0; i < NUM_FB; i++) begin
if (fill_ext_arb[i]) begin
fill_ext_req_addr |= {fill_addr_q[i][ADDR_W-1:LINE_W], fill_ext_off[i]};
end
end
end
// Cache req info
always_comb begin
fill_ram_req_addr = '0;
fill_ram_req_way = '0;
fill_ram_req_data = '0;
for (int i = 0; i < NUM_FB; i++) begin
if (fill_ram_arb[i]) begin
fill_ram_req_addr |= fill_addr_q[i];
fill_ram_req_way |= fill_way_q[i];
fill_ram_req_data |= fill_data_q[i];
end
end
end
// IF stage output data
always_comb begin
fill_out_data = '0;
fill_out_err = '0;
for (int i = 0; i < NUM_FB; i++) begin
if (fill_data_reg[i]) begin
fill_out_data |= fill_data_q[i];
// Ignore any speculative errors accumulated on cache hits
fill_out_err |= (fill_err_q[i] & ~{LINE_BEATS{fill_hit_q[i]}});
end
end
end
///////////////////////
// External requests //
///////////////////////
assign instr_req = ((SpecRequest | branch_i) & lookup_grant_ic0) |
|fill_ext_req;
assign instr_addr = |fill_ext_req ? fill_ext_req_addr :
lookup_addr_ic0[ADDR_W-1:BUS_W];
assign instr_req_o = instr_req;
assign instr_addr_o = {instr_addr[ADDR_W-1:BUS_W],{BUS_W{1'b0}}};
////////////////////////
// Output data muxing //
////////////////////////
// Mux between line-width data sources
assign line_data = |fill_data_hit ? hit_data_ic1[LineSize-1:0] : fill_out_data;
assign line_err = |fill_data_hit ? {LINE_BEATS{1'b0}} : fill_out_err;
// Mux the relevant beat of line data, based on the output address
always_comb begin
line_data_muxed = '0;
line_err_muxed = 1'b0;
for (int i = 0; i < LINE_BEATS; i++) begin
// When data has been skidded, the output address is behind by one
if ((output_addr_q[LINE_W-1:BUS_W] + {{LINE_BEATS_W-1{1'b0}},skid_valid_q}) ==
i[LINE_BEATS_W-1:0]) begin
line_data_muxed |= line_data[i*32+:32];
line_err_muxed |= line_err[i];
end
end
end
// Mux between incoming rdata and the muxed line data
assign output_data = |fill_data_rvd ? instr_rdata_i : line_data_muxed;
assign output_err = |fill_data_rvd ? instr_err_i : line_err_muxed;
// Output data is valid (from any of the three possible sources). Note that fill_out_arb
// must be used here rather than fill_out_req because data can become valid out of order
// (e.g. cache hit data can become available ahead of an older outstanding miss).
assign data_valid = |fill_out_arb;
// Skid buffer data
assign skid_data_d = output_data[31:16];
assign skid_en = data_valid & (ready_i | skid_ready);
always_ff @(posedge clk_i) begin
if (skid_en) begin
skid_data_q <= skid_data_d;
skid_err_q <= output_err;
end
end
// The data in the skid buffer is ready if it's a complete compressed instruction or if there's
// an error (no need to wait for the second half)
assign skid_complete_instr = skid_valid_q & ((skid_data_q[1:0] != 2'b11) | skid_err_q);
// Data can be loaded into the skid buffer for an unaligned uncompressed instruction
assign skid_ready = output_addr_q[1] & ~skid_valid_q & (~output_compressed | output_err);
assign output_ready = (ready_i | skid_ready) & ~skid_complete_instr;
assign output_compressed = (rdata_o[1:0] != 2'b11);
assign skid_valid_d =
// Branches invalidate the skid buffer
branch_i ? 1'b0 :
// Once valid, the skid buffer stays valid until a compressed instruction realigns the stream
(skid_valid_q ? ~(ready_i & ((skid_data_q[1:0] != 2'b11) | skid_err_q)) :
// The skid buffer becomes valid when:
// - we branch to an unaligned uncompressed instruction
(((output_addr_q[1] & (~output_compressed | output_err)) |
// - a compressed instruction misaligns the stream
(~output_addr_q[1] & output_compressed & ~output_err & ready_i)) & data_valid));
always_ff @(posedge clk_i or negedge rst_ni) begin
if (!rst_ni) begin
skid_valid_q <= 1'b0;
end else begin
skid_valid_q <= skid_valid_d;
end
end
// Signal that valid data is available to the IF stage
// Note that if the first half of an unaligned instruction reports an error, we do not need
// to wait for the second half (and for PMP errors we might not have fetched the second half)
// Compressed instruction completely satisfied by skid buffer
assign output_valid = skid_complete_instr |
// Output data available and, output stream aligned, or skid data available,
(data_valid & (~output_addr_q[1] | skid_valid_q |
// or this is an error or an unaligned compressed instruction
output_err | (output_data[17:16] != 2'b11)));
// Update the address on branches and every time an instruction is driven
assign output_addr_en = branch_i | (ready_i & valid_o);
// Increment the address by two every time a compressed instruction is popped
assign addr_incr_two = output_compressed & ~err_o;
assign output_addr_d = branch_i ? addr_i[31:1] :
(output_addr_q[31:1] +
// Increment address by 4 or 2
{29'd0, ~addr_incr_two, addr_incr_two});
always_ff @(posedge clk_i) begin
if (output_addr_en) begin
output_addr_q <= output_addr_d;
end
end
// Mux the data from BusWidth to halfword
// This muxing realigns data when instruction words are split across BUS_W e.g.
// word 1 |----|*h1*|
// word 0 |*h0*|----| --> |*h1*|*h0*|
// 31 15 0 31 15 0
always_comb begin
output_data_lo = '0;
for (int i = 0; i < OUTPUT_BEATS; i++) begin
if (output_addr_q[BUS_W-1:1] == i[BUS_W-2:0]) begin
output_data_lo |= output_data[i*16+:16];
end
end
end
always_comb begin
output_data_hi = '0;
for (int i = 0; i < OUTPUT_BEATS-1; i++) begin
if (output_addr_q[BUS_W-1:1] == i[BUS_W-2:0]) begin
output_data_hi |= output_data[(i+1)*16+:16];
end
end
if (&output_addr_q[BUS_W-1:1]) begin
output_data_hi |= output_data[15:0];
end
end
assign valid_o = output_valid;
assign rdata_o = {output_data_hi, (skid_valid_q ? skid_data_q : output_data_lo)};
assign addr_o = {output_addr_q, 1'b0};
assign err_o = (skid_valid_q & skid_err_q) | (~skid_complete_instr & output_err);
// Error caused by the second half of a misaligned uncompressed instruction
// (only relevant when err_o is set)
assign err_plus2_o = skid_valid_q & ~skid_err_q;
///////////////////
// Invalidations //
///////////////////
// Invalidate on reset, or when instructed. If an invalidation request is received while a
// previous invalidation is ongoing, it does not need to be restarted.
assign start_inval = (~reset_inval_q | icache_inval_i) & ~inval_prog_q;
assign inval_prog_d = start_inval | (inval_prog_q & ~inval_done);
assign inval_done = &inval_index_q;
assign inval_index_d = start_inval ? '0 :
(inval_index_q + {{INDEX_W-1{1'b0}},1'b1});
always_ff @(posedge clk_i or negedge rst_ni) begin
if (!rst_ni) begin
inval_prog_q <= 1'b0;
reset_inval_q <= 1'b0;
end else begin
inval_prog_q <= inval_prog_d;
reset_inval_q <= 1'b1;
end
end
always_ff @(posedge clk_i) begin
if (inval_prog_d) begin
inval_index_q <= inval_index_d;
end
end
/////////////////
// Busy status //
/////////////////
// Only busy (for WFI purposes) while an invalidation is in-progress, or external requests are
// outstanding.
assign busy_o = inval_prog_q | (|(fill_busy_q & ~fill_rvd_done));
////////////////
// Assertions //
////////////////
`ASSERT_INIT(size_param_legal, (LineSize > 32))
// ECC primitives will need to be changed for different sizes
`ASSERT_INIT(ecc_tag_param_legal, (TAG_SIZE <= 27))
`ASSERT_INIT(ecc_data_param_legal, (LineSize <= 121))
// Lookups in the tag ram should always give a known result
`ASSERT_KNOWN(TagHitKnown, lookup_valid_ic1 & tag_hit_ic1)
`ASSERT_KNOWN(TagInvalidKnown, lookup_valid_ic1 & tag_invalid_ic1)
// This is only used for the Yosys-based formal flow. Once we have working bind support, we can
// get rid of it.
`ifdef FORMAL
`ifdef YOSYS
// Unfortunately, Yosys doesn't support passing unpacked arrays as ports. Explicitly pack up the
// signals we need.
logic [NUM_FB-1:0][ADDR_W-1:0] packed_fill_addr_q;
always_comb begin
for (int i = 0; i < NUM_FB; i++) begin
packed_fill_addr_q[i][ADDR_W-1:0] = fill_addr_q[i];
end
end
`include "formal_tb_frag.svh"
`endif
`endif
endmodule