[clocking] Add a fragment to set bus clock-sink freqs more intuitively

generators/chipyard/src/main/scala/ConfigFragments.scala

@@ -1,5 +1,6 @@
 package chipyard.config
 
+import scala.util.matching.Regex
 import chisel3._
 import chisel3.util.{log2Up}
 
@@ -11,6 +12,7 @@ import freechips.rocketchip.devices.debug.{Debug, ExportDebug, DebugModuleKey, D
 import freechips.rocketchip.groundtest.{GroundTestSubsystem}
 import freechips.rocketchip.tile._
 import freechips.rocketchip.rocket.{RocketCoreParams, MulDivParams, DCacheParams, ICacheParams}
+import freechips.rocketchip.tilelink.{HasTLBusParams}
 import freechips.rocketchip.util.{AsyncResetReg, Symmetric}
 import freechips.rocketchip.prci._
 
@@ -183,6 +185,34 @@ class WithPeripheryBusFrequencyAsDefault extends Config((site, here, up) => {
   case DefaultClockFrequencyKey => (site(PeripheryBusKey).dtsFrequency.get / (1000 * 1000)).toDouble
 })
 
+class WithSystemBusFrequencyAsDefault extends Config((site, here, up) => {
+  case DefaultClockFrequencyKey => (site(SystemBusKey).dtsFrequency.get / (1000 * 1000)).toDouble
+})
+
+class BusFrequencyAssignment[T <: HasTLBusParams](re: Regex, key: Field[T]) extends Config((site, here, up) => {
+  case ClockFrequencyAssignersKey => up(ClockFrequencyAssignersKey, site) ++
+    Seq((cName: String) => site(key).dtsFrequency.flatMap { f =>
+      re.findFirstIn(cName).map {_ => (f / (1000 * 1000)).toDouble }
+    })
+})
+
+/**
+  * Provides a diplomatic frequency for all clock sinks with an unspecified
+  * frequency bound to each bus.
+  *
+  * For example, the L2 cache, when bound to the sbus, receives a separate
+  * clock that appears as "subsystem_sbus_<num>".  This fragment ensures that
+  * clock requests the same frequency as the sbus itself.
+  */
+
+class WithInheritBusFrequencyAssignments extends Config(
+  new BusFrequencyAssignment("subsystem_sbus_\\d+".r, SystemBusKey) ++
+  new BusFrequencyAssignment("subsystem_pbus_\\d+".r, PeripheryBusKey) ++
+  new BusFrequencyAssignment("subsystem_cbus_\\d+".r, ControlBusKey) ++
+  new BusFrequencyAssignment("subsystem_fbus_\\d+".r, FrontBusKey) ++
+  new BusFrequencyAssignment("subsystem_mbus_\\d+".r, MemoryBusKey)
+)
+
 /**
   * Mixins to specify crossing types between the 5 traditional TL buses
   *

generators/chipyard/src/main/scala/Subsystem.scala

@@ -69,7 +69,7 @@ class ChipyardSubsystem(implicit p: Parameters) extends BaseSubsystem
   // driveClockFromMaster = Some(true) results in all cbus-attached device and
   // bus clocks to be given names of the form "subsystem_sbus_[0-9]*".
   // Conversly, if an async crossing is used, they instead receive names of the
-  // form "subsystem_cbus_[0-9]*". The assignment below the latter names in all cases.
+  // form "subsystem_cbus_[0-9]*". The assignment below provides the latter names in all cases.
   Seq(PBUS, FBUS, MBUS, CBUS).foreach { loc =>
     tlBusWrapperLocationMap.lift(loc).foreach { _.clockGroupNode := asyncClockGroupsNode }
   }