uart: use PeripheryBusParams.frequency to calculate default divisor (#28)

[sifive-blocks.git] / src / main / scala / devices / uart / UART.scala

diff --git a/src/main/scala/devices/uart/UART.scala b/src/main/scala/devices/uart/UART.scala
index 9b3dfaa37110cb6bdd7c93f7baf99fbda52908c8..58722e112eaafe5edebaf9b121b6162b2edd853b 100644 (file)
--- a/src/main/scala/devices/uart/UART.scala
+++ b/src/main/scala/devices/uart/UART.scala
@@ -2,10 +2,10 @@
 package sifive.blocks.devices.uart
 
 import Chisel._
-import config._
-import regmapper._
-import uncore.tilelink2._
-import util._
+import freechips.rocketchip.config.Parameters
+import freechips.rocketchip.regmapper._
+import freechips.rocketchip.tilelink._
+import freechips.rocketchip.util._
 
 import sifive.blocks.util.{NonBlockingEnqueue, NonBlockingDequeue}
 
@@ -13,6 +13,7 @@ case class UARTParams(
   address: BigInt,
   dataBits: Int = 8,
   stopBits: Int = 2,
+  divisorInit: Int = 0,
   divisorBits: Int = 16,
   oversample: Int = 4,
   nSamples: Int = 3,
@@ -23,6 +24,7 @@ trait HasUARTParameters {
   def c: UARTParams
   def uartDataBits = c.dataBits
   def uartStopBits = c.stopBits
+  def uartDivisorInit = c.divisorInit
   def uartDivisorBits = c.divisorBits
 
   def uartOversample = c.oversample
@@ -32,6 +34,7 @@ trait HasUARTParameters {
   def uartNTxEntries = c.nTxEntries
   def uartNRxEntries = c.nRxEntries
 
+  require(uartDivisorInit != 0) // should have been initialized during instantiation
   require(uartDivisorBits > uartOversample)
   require(uartOversampleFactor > uartNSamples)
 }
@@ -203,8 +206,7 @@ trait HasUARTTopModuleContents extends Module with HasUARTParameters with HasReg
   val rxm = Module(new UARTRx(params))
   val rxq = Module(new Queue(rxm.io.out.bits, uartNRxEntries))
 
-  val divinit = 542 // (62.5MHz / 115200)
-  val div = Reg(init = UInt(divinit, uartDivisorBits))
+  val div = Reg(init = UInt(uartDivisorInit, uartDivisorBits))
 
   private val stopCountBits = log2Up(uartStopBits)
   private val txCountBits = log2Floor(uartNTxEntries) + 1