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tilelink2: Fragmenter should not cut Acquire parameters

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The correct response to misuse is to fail a requirement check.
Pretending that things are not caches could lead to inconsistency.
This commit is contained in:
Wesley W. Terpstra 2016-10-10 11:46:26 -07:00
parent 6336f94fa2
commit 4caa543ad7
1 changed files with 4 additions and 11 deletions
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15
src/main/scala/uncore/tilelink2/Fragmenter.scala
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@ -12,7 +12,7 @@ import scala.math.{min,max}
// alwaysMin: fragment all requests down to minSize (else fragment to maximum supported by manager) // alwaysMin: fragment all requests down to minSize (else fragment to maximum supported by manager)
// Fragmenter modifies: PutFull, PutPartial, LogicalData, Get, Hint // Fragmenter modifies: PutFull, PutPartial, LogicalData, Get, Hint
// Fragmenter passes: ArithmeticData (truncated to minSize if alwaysMin) // Fragmenter passes: ArithmeticData (truncated to minSize if alwaysMin)
// Fragmenter breaks: Acquire (and thus cuts BCE channels) // Fragmenter cannot modify acquire (could livelock); thus it is unsafe to put caches on both sides
class TLFragmenter(minSize: Int, maxSize: Int, alwaysMin: Boolean = false) extends LazyModule class TLFragmenter(minSize: Int, maxSize: Int, alwaysMin: Boolean = false) extends LazyModule
{ {
require (isPow2 (maxSize)) require (isPow2 (maxSize))
@ -30,7 +30,6 @@ class TLFragmenter(minSize: Int, maxSize: Int, alwaysMin: Boolean = false) exten
if (x.min <= minSize) TransferSizes(x.min, min(minSize, x.max)) else if (x.min <= minSize) TransferSizes(x.min, min(minSize, x.max)) else
TransferSizes.none TransferSizes.none
def mapManager(m: TLManagerParameters) = m.copy( def mapManager(m: TLManagerParameters) = m.copy(
supportsAcquire = TransferSizes.none, // this adapter breaks acquires
supportsArithmetic = shrinkTransfer(m.supportsArithmetic), supportsArithmetic = shrinkTransfer(m.supportsArithmetic),
supportsLogical = expandTransfer(m.supportsLogical), supportsLogical = expandTransfer(m.supportsLogical),
supportsGet = expandTransfer(m.supportsGet), supportsGet = expandTransfer(m.supportsGet),
@ -38,15 +37,7 @@ class TLFragmenter(minSize: Int, maxSize: Int, alwaysMin: Boolean = false) exten
supportsPutPartial = expandTransfer(m.supportsPutPartial), supportsPutPartial = expandTransfer(m.supportsPutPartial),
supportsHint = expandTransfer(m.supportsHint)) supportsHint = expandTransfer(m.supportsHint))
def mapClient(c: TLClientParameters) = c.copy( def mapClient(c: TLClientParameters) = c.copy(
sourceId = IdRange(c.sourceId.start << fragmentBits, c.sourceId.end << fragmentBits), sourceId = IdRange(c.sourceId.start << fragmentBits, c.sourceId.end << fragmentBits))
// since we break Acquires, none of these work either:
supportsProbe = TransferSizes.none,
supportsArithmetic = TransferSizes.none,
supportsLogical = TransferSizes.none,
supportsGet = TransferSizes.none,
supportsPutFull = TransferSizes.none,
supportsPutPartial = TransferSizes.none,
supportsHint = TransferSizes.none)
// Because the Fragmenter stalls inner A while serving outer, it can wipe away inner latency // Because the Fragmenter stalls inner A while serving outer, it can wipe away inner latency
val node = TLAdapterNode( val node = TLAdapterNode(
@ -70,6 +61,8 @@ class TLFragmenter(minSize: Int, maxSize: Int, alwaysMin: Boolean = false) exten
// We don't support fragmenting to sub-beat accesses // We don't support fragmenting to sub-beat accesses
require (minSize >= beatBytes) require (minSize >= beatBytes)
// We can't support devices which are cached on both sides of us
require (!edgeOut.manager.anySupportAcquire || !edgeIn.client.anySupportProbe)
/* The Fragmenter is a bit tricky, because there are 5 sizes in play: /* The Fragmenter is a bit tricky, because there are 5 sizes in play:
* max size -- the maximum transfer size possible * max size -- the maximum transfer size possible