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rocket-chip/rocket/src/main/scala/icache.scala

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5.3 KiB
Scala
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package Top {
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import Chisel._;
import Node._;
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import Constants._;
import scala.math._;
// interface between I$ and pipeline/ITLB (32 bits wide)
class ioImem(view: List[String] = null) extends Bundle (view)
{
val invalidate = Bool(INPUT);
val itlb_miss = Bool(INPUT);
val req_val = Bool(INPUT);
val req_idx = Bits(PGIDX_BITS, INPUT);
val req_ppn = Bits(PPN_BITS, INPUT);
val resp_data = Bits(32, OUTPUT);
val resp_val = Bool(OUTPUT);
}
// interface between I$ and memory (128 bits wide)
class ioIcache(view: List[String] = null) extends Bundle (view)
{
val req_addr = UFix(PADDR_BITS - OFFSET_BITS, INPUT);
val req_val = Bool(INPUT);
val req_rdy = Bool(OUTPUT);
val resp_data = Bits(MEM_DATA_BITS, OUTPUT);
val resp_val = Bool(OUTPUT);
}
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class ioICache extends Bundle()
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{
val cpu = new ioImem();
val mem = new ioIcache().flip();
}
// basic direct mapped instruction cache
// 32 bit wide cpu port, 128 bit wide memory port, 64 byte cachelines
// parameters :
// lines = # cache lines
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class rocketICache(sets: Int, assoc: Int) extends Component {
val io = new ioICache();
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val lines = sets * assoc;
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val addrbits = PADDR_BITS;
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val indexbits = log2up(sets);
val offsetbits = OFFSET_BITS;
val tagmsb = addrbits - 1;
val taglsb = indexbits+offsetbits;
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val tagbits = addrbits-taglsb;
val indexmsb = taglsb-1;
val indexlsb = offsetbits;
val offsetmsb = indexlsb-1;
val databits = 32;
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val offsetlsb = log2up(databits/8);
val rf_cnt_bits = log2up(REFILL_CYCLES);
require(PGIDX_BITS >= taglsb); // virtually-indexed, physically-tagged constraint
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require(ispow2(sets) && ispow2(assoc));
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val s_reset :: s_ready :: s_request :: s_refill_wait :: s_refill :: Nil = Enum(5) { UFix() };
val state = Reg(resetVal = s_reset);
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val r_cpu_req_idx = Reg { Bits() }
val r_cpu_req_ppn = Reg { Bits() }
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val r_cpu_req_val = Reg(resetVal = Bool(false));
val rdy = Wire() { Bool() }
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val tag_hit = Wire() { Bool() }
when (io.cpu.req_val && rdy) {
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r_cpu_req_val <== Bool(true)
r_cpu_req_idx <== io.cpu.req_idx
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}
otherwise {
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r_cpu_req_val <== Bool(false)
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}
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when (state === s_ready && r_cpu_req_val && !io.cpu.itlb_miss) {
r_cpu_req_ppn <== io.cpu.req_ppn
}
val r_cpu_hit_addr = Cat(io.cpu.req_ppn, r_cpu_req_idx)
val r_cpu_hit_tag = r_cpu_hit_addr(tagmsb,taglsb)
val r_cpu_miss_addr = Cat(r_cpu_req_ppn, r_cpu_req_idx)
val r_cpu_miss_tag = r_cpu_miss_addr(tagmsb,taglsb)
// refill counter
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val refill_count = Reg(resetVal = UFix(0, rf_cnt_bits));
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when (io.mem.resp_val) {
refill_count <== refill_count + UFix(1);
}
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val repl_way = LFSR16(state === s_ready && r_cpu_req_val && !io.cpu.itlb_miss && !tag_hit)(log2up(assoc)-1,0)
val word_shift = Cat(r_cpu_req_idx(offsetmsb-rf_cnt_bits,offsetlsb), UFix(0, log2up(databits))).toUFix
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val tag_addr =
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Mux((state === s_refill_wait), r_cpu_req_idx(indexmsb,indexlsb),
io.cpu.req_idx(indexmsb,indexlsb)).toUFix;
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val tag_we = (state === s_refill_wait) && io.mem.resp_val;
val data_addr =
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Mux((state === s_refill_wait) || (state === s_refill), Cat(r_cpu_req_idx(indexmsb,offsetbits), refill_count),
io.cpu.req_idx(indexmsb, offsetbits-rf_cnt_bits)).toUFix;
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val data_mux = (new Mux1H(assoc)){Bits(width = MEM_DATA_BITS)}
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var any_hit = Bool(false)
for (i <- 0 until assoc)
{
val repl_me = (repl_way === UFix(i))
val tag_array = Mem4(lines, r_cpu_miss_tag);
tag_array.setReadLatency(1);
tag_array.setTarget('inst);
val tag_rdata = tag_array.rw(tag_addr, r_cpu_miss_tag, tag_we && repl_me);
// valid bit array
val vb_array = Reg(resetVal = Bits(0, lines));
when (io.cpu.invalidate) {
vb_array <== Bits(0,lines);
}
when (tag_we && repl_me) {
vb_array <== vb_array.bitSet(r_cpu_req_idx(indexmsb,indexlsb).toUFix, UFix(1,1));
}
val valid = vb_array(r_cpu_req_idx(indexmsb,indexlsb)).toBool;
val hit = valid && (tag_rdata === r_cpu_hit_addr(tagmsb,taglsb))
// data array
val data_array = Mem4(lines*REFILL_CYCLES, io.mem.resp_data);
data_array.setReadLatency(1);
data_array.setTarget('inst);
val data_out = data_array.rw(data_addr, io.mem.resp_data, io.mem.resp_val && repl_me)
data_mux.io.sel(i) := hit
data_mux.io.in(i) := (data_out >> word_shift)(databits-1,0);
any_hit = any_hit || hit
}
tag_hit := any_hit
// output signals
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io.cpu.resp_val := !io.cpu.itlb_miss && (state === s_ready) && r_cpu_req_val && tag_hit;
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rdy := !io.cpu.itlb_miss && (state === s_ready) && (!r_cpu_req_val || tag_hit);
io.cpu.resp_data := data_mux.io.out
io.mem.req_val := (state === s_request);
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io.mem.req_addr := r_cpu_miss_addr(tagmsb,indexlsb).toUFix
// control state machine
switch (state) {
is (s_reset) {
state <== s_ready;
}
is (s_ready) {
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when (io.cpu.itlb_miss) {
state <== s_ready;
}
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when (r_cpu_req_val && !tag_hit) {
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state <== s_request;
}
}
is (s_request)
{
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when (io.mem.req_rdy) {
state <== s_refill_wait;
}
}
is (s_refill_wait) {
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when (io.mem.resp_val) {
state <== s_refill;
}
}
is (s_refill) {
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when (io.mem.resp_val && (~refill_count === UFix(0))) {
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state <== s_ready;
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}
}
}
}
}