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CacheCork: better document edge conditions

This commit is contained in:
Wesley W. Terpstra 2018-02-15 19:14:30 -08:00
parent ecd069dca4
commit dcfbdabe60
1 changed files with 12 additions and 5 deletions
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17
src/main/scala/tilelink/CacheCork.scala
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@ -26,10 +26,10 @@ class TLCacheCork(unsafe: Boolean = false)(implicit p: Parameters) extends LazyM
(node.in zip node.out) foreach { case ((in, edgeIn), (out, edgeOut)) =>
val clients = edgeIn.client.clients
val caches = clients.filter(_.supportsProbe)
require (clients.size == 1 || caches.size == 0 || unsafe, "Only one client can safely use a TLCacheCork")
require (caches.size <= 1 || unsafe, "Only one caching client allowed")
require (clients.size == 1 || caches.size == 0 || unsafe, s"Only one client can safely use a TLCacheCork; ${clients.map(_.name)}")
require (caches.size <= 1 || unsafe, s"Only one caching client allowed; ${clients.map(_.name)}")
edgeOut.manager.managers.foreach { case m =>
require (!m.supportsAcquireB || unsafe, "Cannot support caches beyond the Cork")
require (!m.supportsAcquireB || unsafe, s"Cannot support caches beyond the Cork; ${m.name}")
require (m.regionType <= RegionType.UNCACHED)
}
@ -39,8 +39,15 @@ class TLCacheCork(unsafe: Boolean = false)(implicit p: Parameters) extends LazyM
// A caveat is that we get Acquire+Release with the same source and must keep the
// source unique after transformation onto the A channel.
// The coding scheme is:
// Put: 1, Release: 0 => AccessAck
// *: 0, Acquire: 1 => AccessAckData
// Release, AcquireBlock.BtoT, AcquirePerm => instant response
// Put{Full,Partial}Data: 1, ReleaseData: 0 => AccessAck
// {Arithmetic,Logical}Data,Get: 0, Acquire: 1 => AccessAckData
// Hint:0 => HintAck
// The CacheCork can potentially send the same source twice if a client sends
// simultaneous Release and AMO/Get with the same source. It will still correctly
// decode the messages based on the D.opcode, but the double use violates the spec.
// Fortunately, no masters we know of behave this way!
// Take requests from A to A or D (if BtoT Acquire)
val a_a = Wire(out.a)