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Merge pull request #837 from freechipsproject/plic_recode

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plic: Recode to use OH knowledge
This commit is contained in:
Megan Wachs 2017-06-30 16:05:32 -07:00 committed by GitHub
commit 69ab3626ca
1 changed files with 37 additions and 14 deletions
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49
src/main/scala/uncore/devices/Plic.scala
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@ -147,12 +147,6 @@ class TLPLIC(params: PLICParams)(implicit p: Parameters) extends LazyModule
val pending = Reg(init=Vec.fill(nDevices+1){Bool(false)})
val enables = Reg(Vec(nHarts, Vec(nDevices+1, Bool())))
for ((p, g) <- pending zip gateways) {
g.ready := !p
g.complete := false
when (g.valid) { p := true }
}
def findMax(x: Seq[UInt]): (UInt, UInt) = {
if (x.length > 1) {
val half = 1 << (log2Ceil(x.length) - 1)
@ -181,21 +175,50 @@ class TLPLIC(params: PLICParams)(implicit p: Parameters) extends LazyModule
PLICConsts.enableBase(i) -> e.map(b => RegField(1, b))
}
// When a hart reads a claim/complete register, then the
// device which is currently its highest priority is no longer pending.
// 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.
val claimer = Wire(Vec(nHarts, Bool()))
assert((claimer.asUInt & (claimer.asUInt - UInt(1))) === UInt(0)) // One-Hot
val claiming = Vec.tabulate(nHarts){i => Mux(claimer(i), UIntToOH(maxDevs(i), nDevices+1), UInt(0))}
val claimedDevs = Vec(claiming.reduceLeft( _ | _ ).toBools)
((pending zip gateways) zip claimedDevs) foreach { case ((p, g), c) =>
g.ready := !p
when (c || g.valid) { p := !c }
}
// 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 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 completedDevs = Mux(completer.reduce(_ || _), UIntToOH(completerDev, nDevices+1), UInt(0))
(gateways zip completedDevs.toBools) foreach { case (g, c) =>
g.complete := c
}
val hartRegFields = Seq.tabulate(nHarts) { i =>
PLICConsts.hartBase(i) -> Seq(
priorityRegField(threshold(i)),
RegField(32,
RegReadFn { valid =>
when (valid) {
pending(maxDevs(i)) := Bool(false)
}
claimer(i) := valid
(Bool(true), maxDevs(i))
},
RegWriteFn { (valid, data) =>
val irq = data.extract(log2Ceil(nDevices+1)-1, 0)
when (valid && enables(i)(irq)) {
gateways(irq).complete := Bool(true)
}
assert(completerDev === data.extract(log2Ceil(nDevices+1)-1, 0),
"completerDev should be consistent for all harts")
completerDev := data.extract(log2Ceil(nDevices+1)-1, 0)
completer(i) := valid && enables(i)(completerDev)
Bool(true)
}
)