Add support for per-way cache metadata
Exposes new parameter field SplitMetadata to determine whether the metadata array in a particular cache is stored in a single SeqMem or with one SeqMem per way. Closes #14
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@ -20,6 +20,7 @@ case object CacheBlockOffsetBits extends Field[Int]
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case object ECCCode extends Field[Option[Code]]
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case object CacheIdBits extends Field[Int]
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case object CacheId extends Field[Int]
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case object SplitMetadata extends Field[Boolean]
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trait HasCacheParameters {
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implicit val p: Parameters
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@ -36,6 +37,7 @@ trait HasCacheParameters {
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val rowBytes = rowBits/8
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val rowOffBits = log2Up(rowBytes)
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val code = p(ECCCode).getOrElse(new IdentityCode)
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val hasSplitMetadata = p(SplitMetadata)
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}
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abstract class CacheModule(implicit val p: Parameters) extends Module
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@ -128,10 +130,10 @@ abstract class Metadata(implicit p: Parameters) extends CacheBundle()(p) {
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class MetaReadReq(implicit p: Parameters) extends CacheBundle()(p) {
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val idx = Bits(width = idxBits)
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val way_en = Bits(width = nWays)
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}
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class MetaWriteReq[T <: Metadata](gen: T)(implicit p: Parameters) extends MetaReadReq()(p) {
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val way_en = Bits(width = nWays)
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val data = gen.cloneType
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override def cloneType = new MetaWriteReq(gen)(p).asInstanceOf[this.type]
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}
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@ -148,16 +150,31 @@ class MetadataArray[T <: Metadata](onReset: () => T)(implicit p: Parameters) ext
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val waddr = Mux(rst, rst_cnt, io.write.bits.idx)
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val wdata = Mux(rst, rstVal, io.write.bits.data).toBits
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val wmask = Mux(rst, SInt(-1), io.write.bits.way_en.toSInt).toBools
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val rmask = Mux(rst, SInt(-1), io.read.bits.way_en.toSInt).toBools
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when (rst) { rst_cnt := rst_cnt+UInt(1) }
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val metabits = rstVal.getWidth
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val tag_arr = SeqMem(nSets, Vec(nWays, UInt(width = metabits)))
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when (rst || io.write.valid) {
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tag_arr.write(waddr, Vec.fill(nWays)(wdata), wmask)
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if (hasSplitMetadata) {
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val tag_arrs = List.fill(nWays){ SeqMem(nSets, UInt(width = metabits)) }
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val tag_readout = Wire(Vec(nWays,rstVal.cloneType))
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val tags_vec = Wire(Vec.fill(nWays)(UInt(width = metabits)))
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(0 until nWays).foreach { (i) =>
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when (rst || (io.write.valid && wmask(i))) {
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tag_arrs(i).write(waddr, wdata)
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}
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tags_vec(i) := tag_arrs(i).read(io.read.bits.idx, io.read.valid && rmask(i))
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}
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io.resp := io.resp.fromBits(tags_vec.toBits)
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} else {
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val tag_arr = SeqMem(nSets, Vec(nWays, UInt(width = metabits)))
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when (rst || io.write.valid) {
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tag_arr.write(waddr, Vec.fill(nWays)(wdata), wmask)
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}
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val tags = tag_arr.read(io.read.bits.idx, io.read.valid).toBits
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io.resp := io.resp.fromBits(tags)
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}
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val tags = tag_arr.read(io.read.bits.idx, io.read.valid).toBits
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io.resp := io.resp.fromBits(tags)
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io.read.ready := !rst && !io.write.valid // so really this could be a 6T RAM
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io.write.ready := !rst
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}
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@ -268,13 +285,16 @@ class L2MetadataArray(implicit p: Parameters) extends L2HellaCacheModule()(p) {
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val meta = Module(new MetadataArray(onReset _))
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meta.io.read <> io.read
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meta.io.write <> io.write
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val way_en_1h = (Vec.fill(nWays){Bool(true)}).toBits
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val s1_way_en_1h = RegEnable(way_en_1h, io.read.valid)
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meta.io.read.bits.way_en := way_en_1h
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val s1_tag = RegEnable(io.read.bits.tag, io.read.valid)
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val s1_id = RegEnable(io.read.bits.id, io.read.valid)
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def wayMap[T <: Data](f: Int => T) = Vec((0 until nWays).map(f))
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val s1_clk_en = Reg(next = io.read.fire())
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val s1_tag_eq_way = wayMap((w: Int) => meta.io.resp(w).tag === s1_tag)
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val s1_tag_match_way = wayMap((w: Int) => s1_tag_eq_way(w) && meta.io.resp(w).coh.outer.isValid()).toBits
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val s1_tag_match_way = wayMap((w: Int) => s1_tag_eq_way(w) && meta.io.resp(w).coh.outer.isValid() && s1_way_en_1h(w).toBool).toBits
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val s1_idx = RegEnable(io.read.bits.idx, io.read.valid) // deal with stalls?
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val s2_tag_match_way = RegEnable(s1_tag_match_way, s1_clk_en)
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val s2_tag_match = s2_tag_match_way.orR
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