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Fix multi-set hit in L1
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micprog committed Feb 27, 2024
1 parent 95035dc commit 585be38
Showing 1 changed file with 26 additions and 10 deletions.
36 changes: 26 additions & 10 deletions src/snitch_icache_lookup_serial.sv
Original file line number Diff line number Diff line change
Expand Up @@ -241,6 +241,11 @@ module snitch_icache_lookup_serial #(
data_rsp_t data_rsp_q;
logic data_valid, data_ready;

logic refill_hit_d, refill_hit_q;
data_rsp_t refill_wdata_q, proper_rdata;
logic [CFG.SET_ALIGN-1:0] write_set_q;
logic write_error_q;

// Connect tag stage response to data stage request
assign data_req_d.addr = tag_req_q.addr;
assign data_req_d.id = tag_req_q.id;
Expand Down Expand Up @@ -286,26 +291,37 @@ module snitch_icache_lookup_serial #(

// Buffer the metadata on a valid handshake. Stall on write (implicit in tag_ready)
`FFL(data_req_q, data_req_d, tag_valid && tag_ready, '0, clk_i, rst_ni)
`FF(data_valid, (tag_valid && !data_write) ? 1'b1 : data_ready ? 1'b0 : data_valid,
'0, clk_i, rst_ni)
// Ready if buffer is empy or downstream is reading. Stall on write
assign tag_ready = (!data_valid || data_ready) && !data_write;
`FF(data_valid, (tag_valid && (!data_write || refill_hit_d)) ?
1'b1 : data_ready ? 1'b0 : data_valid, '0, clk_i, rst_ni)
// Ready if buffer is empty or downstream is reading. Stall on write
assign tag_ready = (!data_valid || data_ready) && (!data_write || refill_hit_d);

// Register the handshake of the tag stage to buffer the data output data in the next cycle
// but only if it was a hit. Otherwise, the data is not read anyway.
`FF(tag_handshake, tag_valid && tag_ready && data_req_d.hit, 1'b0, clk_i, rst_ni)
`FF(tag_handshake, tag_valid && tag_ready && (data_req_d.hit || refill_hit_d),
1'b0, clk_i, rst_ni)

// Fall-through buffer the read data: Store the read data if the SRAM bank accepted a request in
// the previous cycle and if we actually have to buffer them because the receiver is not ready
`FFL(data_rsp_q, data_rdata, tag_handshake && !data_ready, '0, clk_i, rst_ni)
assign out_data_o = tag_handshake ? data_rdata : data_rsp_q;
`FFL(data_rsp_q, proper_rdata, tag_handshake && !data_ready, '0, clk_i, rst_ni)
assign proper_rdata = refill_hit_q && !data_req_q.hit ? refill_wdata_q : data_rdata;
assign out_data_o = tag_handshake ? proper_rdata : data_rsp_q;

// Check immediate refill for possible match
assign refill_hit_d = write_valid_i &&
write_tag_i == required_tag &&
write_addr_i == data_req_d.addr[CFG.LINE_ALIGN +: CFG.COUNT_ALIGN];
`FFL(refill_hit_q, refill_hit_d, tag_valid && tag_ready, '0, clk_i, rst_ni)
`FFL(refill_wdata_q, write_data_i, refill_hit_d, '0, clk_i, rst_ni)
`FFL(write_set_q, write_set_i, refill_hit_d, '0, clk_i, rst_ni)
`FFL(write_error_q, write_error_i, refill_hit_d, '0, clk_i, rst_ni)

// Generate the remaining output signals.
assign out_addr_o = data_req_q.addr;
assign out_id_o = data_req_q.id;
assign out_set_o = data_req_q.cset;
assign out_hit_o = data_req_q.hit;
assign out_error_o = data_req_q.error;
assign out_set_o = refill_hit_q && !data_req_q.hit ? write_set_q : data_req_q.cset;
assign out_hit_o = refill_hit_q || data_req_q.hit;
assign out_error_o = refill_hit_q && !data_req_q.hit ? write_error_q : data_req_q.error;
assign out_valid_o = data_valid;
assign data_ready = out_ready_i;

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