From 6c9c0a2af89f60227cbe3f88edd6cb3c42f87823 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Thu, 19 Jul 2001 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2001-07-19

---
 pc/uarti8250.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/pc/uarti8250.c b/pc/uarti8250.c
index 508df314b62ad4ec23d72df1266755e7890775a5..b2ca39d58a0a3a1f00f37dde8c9d5863308c41a3 100644
--- a/pc/uarti8250.c
+++ b/pc/uarti8250.c
@@ -445,7 +445,7 @@ i8250interrupt(Ureg*, void* arg)
 {
 	Ctlr *ctlr;
 	Uart *uart;
-	int iir, old, r;
+	int iir, lsr, old, r;
 
 	uart = arg;
 
@@ -480,16 +480,24 @@ i8250interrupt(Ureg*, void* arg)
 			break;
 		case Irda:		/* Received Data Available */
 		case Ictoi:		/* Character Time-out Indication */
-			uartrecv(uart, csr8r(ctlr, Rbr));
-			break;
-		case Irls:		/* Receiver Line Status */
-			r = csr8r(ctlr, Lsr);
-			if(r & Oe)
-				uart->oerr++;
-			if(r & Pe)
-				uart->perr++;
-			if(r & Fe)
-				uart->ferr++;
+			/*
+			 * Consume any received data.
+			 * If the received byte came in with a break,
+			 * parity or framing error, throw it away;
+			 * overrun is an indication that something has
+			 * already been tossed.
+			 */
+			while((lsr = csr8r(ctlr, Lsr)) & Dr){
+				if(lsr & Oe)
+					uart->oerr++;
+				if(lsr & Pe)
+					uart->perr++;
+				if(lsr & Fe)
+					uart->ferr++;
+				r = csr8r(ctlr, Rbr);
+				if(!(lsr & (Bi|Fe|Pe)))
+					uartrecv(uart, r);
+			}
 			break;
 		default:
 			iprint("weird uart interrupt 0x%2.2uX\n", iir);
@@ -532,7 +540,7 @@ i8250enable(Uart* uart, int ie)
 			intrenable(ctlr->irq, i8250interrupt, uart, ctlr->tbdf, uart->name);
 			ctlr->iena = 1;
 		}
-		ctlr->sticky[Ier] = Erls|Ethre|Erda;
+		ctlr->sticky[Ier] = Ethre|Erda;
 		ctlr->sticky[Mcr] |= Ie;
 	}
 	else{