From 3dfb6ab8c07bd8b539a15af413e79518f506c2ba Mon Sep 17 00:00:00 2001
From: pk <pk@NetBSD.org>
Date: Mon, 3 Jun 1996 23:48:41 +0000
Subject: [PATCH] Code the residual computation a bit differently.

---
 sys/arch/sparc/dev/dma.c | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/sys/arch/sparc/dev/dma.c b/sys/arch/sparc/dev/dma.c
index e87f0bc923ae..f5fb6f588dd5 100644
--- a/sys/arch/sparc/dev/dma.c
+++ b/sys/arch/sparc/dev/dma.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: dma.c,v 1.28 1996/05/21 19:07:30 pk Exp $ */
+/*	$NetBSD: dma.c,v 1.29 1996/06/03 23:48:41 pk Exp $ */
 
 /*
  * Copyright (c) 1994 Paul Kranenburg.  All rights reserved.
@@ -394,7 +394,7 @@ int
 espdmaintr(sc)
 	struct dma_softc *sc;
 {
-	int trans = 0, resid = 0;
+	int trans, resid;
 	u_long csr;
 	csr = DMACSR(sc);
 
@@ -434,20 +434,35 @@ espdmaintr(sc)
 		return 0;
 	}
 
+	resid = 0;
+	/*
+	 * If a transfer onto the SCSI bus gets interrupted by the device
+	 * (e.g. for a SAVEPOINTER message), the data in the FIFO counts
+	 * as residual since the ESP counter registers get decremented as
+	 * bytes are clocked into the FIFO.
+	 */
 	if (!(csr & D_WRITE) &&
 	    (resid = (ESP_READ_REG(sc->sc_esp, ESP_FFLAG) & ESPFIFO_FF)) != 0) {
 		ESP_DMA(("dmaintr: empty esp FIFO of %d ", resid));
 		ESPCMD(sc->sc_esp, ESPCMD_FLUSH);
 	}
 
-	resid += ESP_READ_REG(sc->sc_esp, ESP_TCL) |
-		 (ESP_READ_REG(sc->sc_esp, ESP_TCM) << 8) |
-		 (sc->sc_esp->sc_rev > ESP100A
-			? (ESP_READ_REG(sc->sc_esp, ESP_TCH) << 16) : 0);
+	if ((sc->sc_esp->sc_espstat & ESPSTAT_TC) == 0) {
+		/*
+		 * `Terminal count' is off, so read the residue
+		 * out of the ESP counter registers.
+		 */
+		resid += ( ESP_READ_REG(sc->sc_esp, ESP_TCL) |
+			  (ESP_READ_REG(sc->sc_esp, ESP_TCM) << 8) |
+			   (sc->sc_esp->sc_rev > ESP100A
+				? (ESP_READ_REG(sc->sc_esp, ESP_TCH) << 16)
+				: 0));
 
-	if (resid == 0 && (sc->sc_esp->sc_rev <= ESP100A) &&
-	    (sc->sc_esp->sc_espstat & ESPSTAT_TC) == 0)
-		resid = 65536;
+		if (resid == 0 && sc->sc_dmasize == 65536 &&
+		    sc->sc_esp->sc_rev <= ESP100A)
+			/* A transfer of 64K is encoded as `TCL=TCM=0' */
+			resid = 65536;
+	}
 
 	trans = sc->sc_dmasize - resid;
 	if (trans < 0) {			/* transferred < 0 ? */