From 8aa3fb3eb707e6a3c72979d870f393398f022479 Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Fri, 1 May 2015 15:58:10 +0200
Subject: [PATCH] com/uart: add tx and rx fifos.

Since ressource usage is low with default depth of 16 (implemented in RAM LUTs) we don't keep old behaviour.
Tested successfully with BIOS and flterm.
---
 misoclib/com/uart/__init__.py | 49 +++++++++++++++++++++++------------
 software/libbase/uart.c       | 15 ++++++-----
 2 files changed, 41 insertions(+), 23 deletions(-)

diff --git a/misoclib/com/uart/__init__.py b/misoclib/com/uart/__init__.py
index bc5c6cd4..16160ebb 100644
--- a/misoclib/com/uart/__init__.py
+++ b/misoclib/com/uart/__init__.py
@@ -3,30 +3,45 @@ from migen.bank.description import *
 from migen.bank.eventmanager import *
 from migen.genlib.record import Record
 from migen.flow.actor import Sink, Source
+from migen.actorlib.fifo import SyncFIFO
 
 
 class UART(Module, AutoCSR):
-    def __init__(self, phy):
+    def __init__(self, phy,
+                 tx_fifo_depth=16,
+                 rx_fifo_depth=16):
         self._rxtx = CSR(8)
+        self._txfull = CSRStatus()
+        self._rxempty = CSRStatus()
 
         self.submodules.ev = EventManager()
-        self.ev.tx = EventSourcePulse()
-        self.ev.rx = EventSourcePulse()
+        self.ev.tx = EventSourceProcess()
+        self.ev.rx = EventSourceProcess()
         self.ev.finalize()
-        ###
-        self.sync += [
-            If(self._rxtx.re,
-                phy.sink.stb.eq(1),
-                phy.sink.data.eq(self._rxtx.r),
-            ).Elif(phy.sink.ack,
-                phy.sink.stb.eq(0)
-            ),
-            If(phy.source.stb,
-                self._rxtx.w.eq(phy.source.data)
-            )
+
+        # # #
+
+        tx_fifo = SyncFIFO([("data", 8)], tx_fifo_depth)
+        self.submodules += tx_fifo
+        self.comb += [
+            tx_fifo.sink.stb.eq(self._rxtx.re),
+            tx_fifo.sink.data.eq(self._rxtx.r),
+            self._txfull.status.eq(~tx_fifo.sink.ack),
+            Record.connect(tx_fifo.source, phy.sink)
         ]
+
+        rx_fifo = SyncFIFO([("data", 8)], rx_fifo_depth)
+        self.submodules += rx_fifo
+        self.comb += [
+            Record.connect(phy.source, rx_fifo.sink),
+            self._rxempty.status.eq(~rx_fifo.source.stb),
+            self._rxtx.w.eq(rx_fifo.source.data),
+            rx_fifo.source.ack.eq(self.ev.rx.clear)
+        ]
+
         self.comb += [
-            self.ev.tx.trigger.eq(phy.sink.stb & phy.sink.ack),
-            self.ev.rx.trigger.eq(phy.source.stb & phy.source.ack),
-            phy.source.ack.eq(~self.ev.rx.pending)
+            # Generate TX IRQ when tx_fifo becomes empty
+            self.ev.tx.trigger.eq(tx_fifo.source.stb),
+            # Generate RX IRQ when rx_fifo becomes non-empty
+            self.ev.rx.trigger.eq(~rx_fifo.source.stb),
         ]
diff --git a/software/libbase/uart.c b/software/libbase/uart.c
index 13dfe3b1..30ea5ef3 100644
--- a/software/libbase/uart.c
+++ b/software/libbase/uart.c
@@ -31,19 +31,22 @@ void uart_isr(void)
 	stat = uart_ev_pending_read();
 
 	if(stat & UART_EV_RX) {
-		rx_buf[rx_produce] = uart_rxtx_read();
-		rx_produce = (rx_produce + 1) & UART_RINGBUFFER_MASK_RX;
-		uart_ev_pending_write(UART_EV_RX);
+		while(!uart_rxempty_read()) {
+			rx_buf[rx_produce] = uart_rxtx_read();
+			rx_produce = (rx_produce + 1) & UART_RINGBUFFER_MASK_RX;
+			uart_ev_pending_write(UART_EV_RX);
+		}
 	}
 
 	if(stat & UART_EV_TX) {
 		uart_ev_pending_write(UART_EV_TX);
-		if(tx_level > 0) {
+		if(tx_level == 0)
+			tx_cts = 1;
+		while(tx_level > 0 && !uart_txfull_read()) {
 			uart_rxtx_write(tx_buf[tx_consume]);
 			tx_consume = (tx_consume + 1) & UART_RINGBUFFER_MASK_TX;
 			tx_level--;
-		} else
-			tx_cts = 1;
+		}
 	}
 }
 
-- 
2.30.2