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plic: Clean up comments and simplify checking

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This commit is contained in:
Megan Wachs
2017-06-30 14:15:26 -07:00
parent 76f8de75e3
commit f31ae008f3
1 changed files with 4 additions and 9 deletions
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13
src/main/scala/uncore/devices/Plic.scala
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@@ -178,7 +178,7 @@ class TLPLIC(params: PLICParams)(implicit p: Parameters) extends LazyModule
// When a hart reads a claim/complete register, then the
// device which is currently its highest priority is no longer pending.
// This code expolits the fact that, practically, only one claim/complete
// This code exploits the fact that, practically, only one claim/complete
// register can be read at a time. We check for this because if the address map
// were to change, it may no longer be true.
// Note: PLIC doesn't care which hart reads the register.
@@ -195,14 +195,13 @@ class TLPLIC(params: PLICParams)(implicit p: Parameters) extends LazyModule
// When a hart writes a claim/complete register, then
// the written device (as long as it is actually enabled for that
// hart) is marked complete.
// This code expolits the fact that, practically, only one claim/complete register
// This code exploits the fact that, practically, only one claim/complete register
// can be written at a time. We check for this because if the address map
// were to change, it may no longer be true.
// Note -- PLIC doesn't care which hart writes the register.
val completer = Wire(Vec(nHarts, Bool()))
assert((completer.asUInt & (completer.asUInt - UInt(1))) === UInt(0)) // One-Hot
val completerDev = Wire(UInt(width = log2Up(nDevices + 1)))
val checkCompleterDev = Wire(Vec(nHarts, UInt(width = log2Up(nDevices + 1)))) // For assertion purposes only.
val completedDevs = Mux(completer.reduce(_ || _), UIntToOH(completerDev, nDevices+1), UInt(0))
(gateways zip completedDevs.toBools) foreach { case (g, c) =>
g.complete := c
@@ -217,19 +216,15 @@ class TLPLIC(params: PLICParams)(implicit p: Parameters) extends LazyModule
(Bool(true), maxDevs(i))
},
RegWriteFn { (valid, data) =>
if (i > 0) {
assert(checkCompleterDev(i-1) === data.extract(log2Ceil(nDevices+1)-1, 0))
}
checkCompleterDev(i) := data.extract(log2Ceil(nDevices+1)-1, 0)
completer(i) := valid && enables(i)(completerDev)
assert(completerDev === data.extract(log2Ceil(nDevices+1)-1, 0), "completerDev should be constant for all harts")
completerDev := data.extract(log2Ceil(nDevices+1)-1, 0)
completer(i) := valid && enables(i)(completerDev)
Bool(true)
}
)
)
}
node.regmap((priorityRegFields ++ pendingRegFields ++ enableRegFields ++ hartRegFields):_*)
priority(0) := 0