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Data cache can now be used without writeback stage

This commit is contained in:
Charles Papon 2019-09-23 15:20:20 +02:00
parent ace963b542
commit bf82829e9e
2 changed files with 31 additions and 22 deletions
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19
src/main/scala/vexriscv/ip/DataCache.scala
View File

@ -24,8 +24,9 @@ case class DataCacheConfig(cacheSize : Int,
earlyDataMux : Boolean = false,
tagSizeShift : Int = 0, //Used to force infering ram
withLrSc : Boolean = false,
withAmo : Boolean = false){
withAmo : Boolean = false,
mergeExecuteMemory : Boolean = false){
assert(!(mergeExecuteMemory && (earlyDataMux || earlyWaysHits)))
assert(!(earlyDataMux && !earlyWaysHits))
def burstSize = bytePerLine*8/memDataWidth
val burstLength = bytePerLine/(memDataWidth/8)
@ -446,7 +447,7 @@ class DataCache(p : DataCacheConfig) extends Component{
}
val stageA = new Area{
def stagePipe[T <: Data](that : T) = RegNextWhen(that, !io.cpu.memory.isStuck)
def stagePipe[T <: Data](that : T) = if(mergeExecuteMemory) CombInit(that) else RegNextWhen(that, !io.cpu.memory.isStuck)
val request = stagePipe(io.cpu.execute.args)
val mask = stagePipe(stage0.mask)
io.cpu.memory.mmuBus.cmd.isValid := io.cpu.memory.isValid
@ -457,16 +458,22 @@ class DataCache(p : DataCacheConfig) extends Component{
val wayHits = earlyWaysHits generate ways.map(way => (io.cpu.memory.mmuBus.rsp.physicalAddress(tagRange) === way.tagsReadRsp.address && way.tagsReadRsp.valid))
val dataMux = earlyDataMux generate MuxOH(wayHits, ways.map(_.dataReadRsp))
val colisions = stagePipe(stage0.colisions) | collisionProcess(io.cpu.memory.address(lineRange.high downto wordRange.low), mask) //Assume the writeback stage will never be unstall memory acces while memory stage is stalled
val colisions = if(mergeExecuteMemory){
stagePipe(stage0.colisions)
} else {
//Assume the writeback stage will never be unstall memory acces while memory stage is stalled
stagePipe(stage0.colisions) | collisionProcess(io.cpu.memory.address(lineRange.high downto wordRange.low), mask)
}
}
val stageB = new Area {
def stagePipe[T <: Data](that : T) = RegNextWhen(that, !io.cpu.writeBack.isStuck)
def ramPipe[T <: Data](that : T) = if(mergeExecuteMemory) CombInit(that) else RegNextWhen(that, !io.cpu.writeBack.isStuck)
val request = RegNextWhen(stageA.request, !io.cpu.writeBack.isStuck)
val mmuRspFreeze = False
val mmuRsp = RegNextWhen(io.cpu.memory.mmuBus.rsp, !io.cpu.writeBack.isStuck && !mmuRspFreeze)
val tagsReadRsp = ways.map(w => stagePipe(w.tagsReadRsp))
val dataReadRsp = !earlyDataMux generate ways.map(w => stagePipe(w.dataReadRsp))
val tagsReadRsp = ways.map(w => ramPipe(w.tagsReadRsp))
val dataReadRsp = !earlyDataMux generate ways.map(w => ramPipe(w.dataReadRsp))
val waysHits = if(earlyWaysHits) stagePipe(B(stageA.wayHits)) else B(tagsReadRsp.map(tag => mmuRsp.physicalAddress(tagRange) === tag.address && tag.valid).asBits())
val waysHit = waysHits.orR
val dataMux = if(earlyDataMux) stagePipe(stageA.dataMux) else MuxOH(waysHits, dataReadRsp)

34
src/main/scala/vexriscv/plugin/DBusCachedPlugin.scala
View File

@ -148,7 +148,7 @@ class DBusCachedPlugin(val config : DataCacheConfig,
redoBranch = pipeline.service(classOf[JumpService]).createJumpInterface(if(pipeline.writeBack != null) pipeline.writeBack else pipeline.execute)
if(catchSomething)
exceptionBus = pipeline.service(classOf[ExceptionService]).newExceptionPort(pipeline.writeBack)
exceptionBus = pipeline.service(classOf[ExceptionService]).newExceptionPort(if(pipeline.writeBack == null) pipeline.memory else pipeline.writeBack)
if(pipeline.serviceExist(classOf[PrivilegeService]))
privilegeService = pipeline.service(classOf[PrivilegeService])
@ -162,7 +162,9 @@ class DBusCachedPlugin(val config : DataCacheConfig,
dBus = master(DataCacheMemBus(this.config)).setName("dBus")
val cache = new DataCache(this.config)
val cache = new DataCache(this.config.copy(
mergeExecuteMemory = writeBack == null
))
//Interconnect the plugin dBus with the cache dBus with some optional pipelining
def optionPipe[T](cond : Boolean, on : T)(f : T => T) : T = if(cond) f(on) else on
@ -226,22 +228,22 @@ class DBusCachedPlugin(val config : DataCacheConfig,
if(relaxedMemoryTranslationRegister) insert(MEMORY_VIRTUAL_ADDRESS) := cache.io.cpu.execute.address
}
val flushStage = if(memory != null) memory else execute
flushStage plug new Area {
import flushStage._
val mmuAndBufferStage = if(writeBack != null) memory else execute
mmuAndBufferStage plug new Area {
import mmuAndBufferStage._
cache.io.cpu.memory.isValid := arbitration.isValid && input(MEMORY_ENABLE)
cache.io.cpu.memory.isStuck := arbitration.isStuck
cache.io.cpu.memory.isRemoved := arbitration.removeIt
cache.io.cpu.memory.address := (if(relaxedMemoryTranslationRegister) input(MEMORY_VIRTUAL_ADDRESS) else U(input(REGFILE_WRITE_DATA)))
cache.io.cpu.memory.address := (if(relaxedMemoryTranslationRegister) input(MEMORY_VIRTUAL_ADDRESS) else if(mmuAndBufferStage == execute) cache.io.cpu.execute.address else U(input(REGFILE_WRITE_DATA)))
cache.io.cpu.memory.mmuBus <> mmuBus
cache.io.cpu.memory.mmuBus.rsp.isIoAccess setWhen(pipeline(DEBUG_BYPASS_CACHE) && !cache.io.cpu.memory.isWrite)
}
val fenceStage = stages.last
fenceStage plug new Area{
import fenceStage._
val managementStage = stages.last
managementStage plug new Area{
import managementStage._
cache.io.cpu.writeBack.isValid := arbitration.isValid && input(MEMORY_ENABLE)
cache.io.cpu.writeBack.isStuck := arbitration.isStuck
cache.io.cpu.writeBack.isUser := (if(privilegeService != null) privilegeService.isUser() else False)
@ -326,10 +328,10 @@ class DBusCachedPlugin(val config : DataCacheConfig,
execute.insert(IS_DBUS_SHARING) := dBusAccess.cmd.fire
mmuBus.cmd.bypassTranslation setWhen(flushStage.input(IS_DBUS_SHARING))
cache.io.cpu.memory.isValid setWhen(flushStage.input(IS_DBUS_SHARING))
cache.io.cpu.writeBack.isValid setWhen(fenceStage.input(IS_DBUS_SHARING))
dBusAccess.rsp.valid := fenceStage.input(IS_DBUS_SHARING) && !cache.io.cpu.writeBack.isWrite && (cache.io.cpu.redo || !cache.io.cpu.writeBack.haltIt)
mmuBus.cmd.bypassTranslation setWhen(mmuAndBufferStage.input(IS_DBUS_SHARING))
if(mmuAndBufferStage != execute) (cache.io.cpu.memory.isValid setWhen(mmuAndBufferStage.input(IS_DBUS_SHARING)))
cache.io.cpu.writeBack.isValid setWhen(managementStage.input(IS_DBUS_SHARING))
dBusAccess.rsp.valid := managementStage.input(IS_DBUS_SHARING) && !cache.io.cpu.writeBack.isWrite && (cache.io.cpu.redo || !cache.io.cpu.writeBack.haltIt)
dBusAccess.rsp.data := cache.io.cpu.writeBack.data
dBusAccess.rsp.error := cache.io.cpu.writeBack.unalignedAccess || cache.io.cpu.writeBack.accessError
dBusAccess.rsp.redo := cache.io.cpu.redo
@ -337,10 +339,10 @@ class DBusCachedPlugin(val config : DataCacheConfig,
when(forceDatapath){
execute.output(REGFILE_WRITE_DATA) := dBusAccess.cmd.address.asBits
}
flushStage.input(IS_DBUS_SHARING) init(False)
fenceStage.input(IS_DBUS_SHARING) init(False)
if(mmuAndBufferStage != execute) mmuAndBufferStage.input(IS_DBUS_SHARING) init(False)
managementStage.input(IS_DBUS_SHARING) init(False)
when(dBusAccess.rsp.valid){
fenceStage.input(IS_DBUS_SHARING).getDrivingReg := False
managementStage.input(IS_DBUS_SHARING).getDrivingReg := False
}
}
}