In article <200501142046.j0EKkTdd021953@egsner.cirr.com>
smj@cirr.com wrote:

> fxp1: WARNING: SCB timed out!
> fxp1: device timeout

How about the attached patch?
---
Izumi Tsutsui
tsutsui@ceres.dti.ne.jp

--- i82557.c.orig	2005-01-19 00:24:59.000000000 +0900
+++ i82557.c	2005-01-19 00:25:10.000000000 +0900
@@ -916,7 +916,7 @@
 			break;
 		m = NULL;
 
-		if (sc->sc_txpending == FXP_NTXCB) {
+		if (sc->sc_txpending == FXP_NTXCB - 1) {
 			FXP_EVCNT_INCR(&sc->sc_ev_txstall);
 			break;
 		}
@@ -1070,7 +1070,7 @@
 #endif
 	}
 
-	if (sc->sc_txpending == FXP_NTXCB) {
+	if (sc->sc_txpending == FXP_NTXCB - 1) {
 		/* No more slots; notify upper layer. */
 		ifp->if_flags |= IFF_OACTIVE;
 	}
@@ -1087,9 +1087,23 @@
 		 * Cause the chip to interrupt and suspend command
 		 * processing once the last packet we've enqueued
 		 * has been transmitted.
+		 *
+		 * To avoid a race between updating status bits
+		 * by the fxp chip and clearing command bits
+		 * by this function on machines which don't have
+		 * atomic methods to clear/set bits in memory
+		 * smaller than 32bits (both cb_status and cb_command
+		 * members are uint16_t and in the same 32bit word),
+		 * we have to prepare a dummy TX descriptor which has
+		 * NOP command and just causes a TX completion interrupt.
 		 */
-		FXP_CDTX(sc, sc->sc_txlast)->txd_txcb.cb_command |=
-		    htole16(FXP_CB_COMMAND_I | FXP_CB_COMMAND_S);
+		sc->sc_txpending++;
+		sc->sc_txlast = FXP_NEXTTX(sc->sc_txlast);
+		txd = FXP_CDTX(sc, sc->sc_txlast);
+		/* BIG_ENDIAN: no need to swap to store 0 */
+		txd->txd_txcb.cb_status = 0;
+		txd->txd_txcb.cb_command = htole16(FXP_CB_COMMAND_NOP |
+		    FXP_CB_COMMAND_I | FXP_CB_COMMAND_S);
 		FXP_CDTXSYNC(sc, sc->sc_txlast,
 		    BUS_DMASYNC_PREREAD|BUS_DMASYNC_PREWRITE);
 
@@ -1221,6 +1235,11 @@
 		FXP_CDTXSYNC(sc, i,
 		    BUS_DMASYNC_POSTREAD|BUS_DMASYNC_POSTWRITE);
 
+		/* skip dummy NOP TX descriptor */
+		if ((le16toh(txd->txd_txcb.cb_command) & FXP_CB_COMMAND_CMD)
+		    == FXP_CB_COMMAND_NOP)
+			continue;
+
 		txstat = le16toh(txd->txd_txcb.cb_status);
 
 		if ((txstat & FXP_CB_STATUS_C) == 0)
--- i82557reg.h.orig	2005-01-19 00:25:22.000000000 +0900
+++ i82557reg.h	2005-01-19 00:25:26.000000000 +0900
@@ -368,6 +368,7 @@
 #define FXP_CB_STATUS_C		0x8000
 
 /* commands */
+#define FXP_CB_COMMAND_CMD	0x0007	/* XXX how about FXPF_IPCB case? */
 #define FXP_CB_COMMAND_NOP	0x0
 #define FXP_CB_COMMAND_IAS	0x1
 #define FXP_CB_COMMAND_CONFIG	0x2