From 5e51e1e93172b5c5b6c436196f8dad68678eb93d Mon Sep 17 00:00:00 2001
From: Yunsup Lee <yunsup@sifive.com>
Date: Tue, 25 Jul 2017 00:56:22 -0700
Subject: [PATCH] uart: use PeripheryBusParams.frequency to calculate default
 divisor (#28)

---
 src/main/scala/devices/uart/UART.scala          | 8 ++++----
 src/main/scala/devices/uart/UARTPeriphery.scala | 7 ++++---
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/main/scala/devices/uart/UART.scala b/src/main/scala/devices/uart/UART.scala
index 1a19be8..58722e1 100644
--- a/src/main/scala/devices/uart/UART.scala
+++ b/src/main/scala/devices/uart/UART.scala
@@ -3,8 +3,6 @@ package sifive.blocks.devices.uart
 
 import Chisel._
 import freechips.rocketchip.config.Parameters
-import freechips.rocketchip.coreplex.RTCPeriod
-import freechips.rocketchip.diplomacy.DTSTimebase
 import freechips.rocketchip.regmapper._
 import freechips.rocketchip.tilelink._
 import freechips.rocketchip.util._
@@ -15,6 +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,
@@ -25,6 +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
@@ -34,6 +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)
 }
@@ -205,8 +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 = p(DTSTimebase) * BigInt(p(RTCPeriod).getOrElse(1)) / 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
diff --git a/src/main/scala/devices/uart/UARTPeriphery.scala b/src/main/scala/devices/uart/UARTPeriphery.scala
index c925a38..677394f 100644
--- a/src/main/scala/devices/uart/UARTPeriphery.scala
+++ b/src/main/scala/devices/uart/UARTPeriphery.scala
@@ -3,7 +3,7 @@ package sifive.blocks.devices.uart
 
 import Chisel._
 import freechips.rocketchip.config.Field
-import freechips.rocketchip.coreplex.{HasPeripheryBus, HasInterruptBus}
+import freechips.rocketchip.coreplex.{HasPeripheryBus, PeripheryBusParams, HasInterruptBus}
 import freechips.rocketchip.diplomacy.{LazyModule, LazyMultiIOModuleImp}
 import sifive.blocks.devices.gpio.{GPIOPin, GPIOOutputPinCtrl, GPIOInputPinCtrl}
 import sifive.blocks.util.ShiftRegisterInit
@@ -11,9 +11,10 @@ import sifive.blocks.util.ShiftRegisterInit
 case object PeripheryUARTKey extends Field[Seq[UARTParams]]
 
 trait HasPeripheryUART extends HasPeripheryBus with HasInterruptBus {
-  val uartParams = p(PeripheryUARTKey)  
+  val uartParams = p(PeripheryUARTKey)
+  val divinit = (p(PeripheryBusParams).frequency / 115200).toInt
   val uarts = uartParams map { params =>
-    val uart = LazyModule(new TLUART(pbus.beatBytes, params))
+    val uart = LazyModule(new TLUART(pbus.beatBytes, params.copy(divisorInit = divinit)))
     uart.node := pbus.toVariableWidthSlaves
     ibus.fromSync := uart.intnode
     uart
-- 
2.30.2