Index: sys/arch/evbarm/dev/plcom.c
===================================================================
RCS file: /cvsroot/src/sys/arch/evbarm/dev/plcom.c,v
retrieving revision 1.40
diff -u -p -u -r1.40 plcom.c
--- sys/arch/evbarm/dev/plcom.c	25 Jul 2012 07:26:17 -0000	1.40
+++ sys/arch/evbarm/dev/plcom.c	11 Aug 2012 08:58:25 -0000
@@ -485,11 +485,16 @@ plcom_attach_subr(struct plcom_softc *sc
 			 * The PL010 has a 16-byte fifo, but the tx interrupt
 			 * triggers when there is space for 8 more bytes.
 			*/
-			sc->sc_fifolen = 8;
+			sc->sc_fifolen = 8;	/* XXX bump to 16? */
+			sc->sc_fifotrigger = 8;
 			break;
 		case PLCOM_TYPE_PL011:
 			/* Some revisions have a 32 byte TX FIFO */
 			sc->sc_fifolen = 16;
+			sc->sc_fifotrigger = 8;
+			PWRITE4(pi, PL011COM_IFLS,
+			    PL011_IFLS_RXIFLS(PL011_IFLS_1HALF) |
+			    PL011_IFLS_TXIFLS(PL011_IFLS_1HALF));
 			break;
 		}
 	}
@@ -2201,8 +2206,8 @@ plcomintr(void *arg)
 				int n;
 
 				n = sc->sc_tbc;
-				if (n > sc->sc_fifolen)
-					n = sc->sc_fifolen;
+				if (n > sc->sc_fifotrigger)
+					n = sc->sc_fifotrigger;
 				PWRITEM1(pi, PL01XCOM_DR, sc->sc_tba, n);
 				sc->sc_tbc -= n;
 				sc->sc_tba += n;
Index: sys/arch/evbarm/dev/plcomreg.h
===================================================================
RCS file: /cvsroot/src/sys/arch/evbarm/dev/plcomreg.h,v
retrieving revision 1.4
diff -u -p -u -r1.4 plcomreg.h
--- sys/arch/evbarm/dev/plcomreg.h	25 Jul 2012 07:26:17 -0000	1.4
+++ sys/arch/evbarm/dev/plcomreg.h	11 Aug 2012 08:58:25 -0000
@@ -106,6 +106,15 @@
 #define	PL01X_MSR_CTS		PL01X_FR_CTS
 #define	PL011_MSR_RI		PL011_FR_RI
 
+/* ifls */
+#define	PL011_IFLS_1EIGTH	0
+#define	PL011_IFLS_1QUARTER	1
+#define	PL011_IFLS_1HALF	2
+#define	PL011_IFLS_3QUARTERS	3
+#define	PL011_IFLS_7EIGTHS	4
+#define	PL011_IFLS_RXIFLS(x)	(((x) & 0x7) << 3)
+#define	PL011_IFLS_TXIFLS(x)	(((x) & 0x7) << 0)
+
 /* All interrupt status/clear registers */
 #define	PL011_INT_OE	0x400
 #define	PL011_INT_BE	0x200
Index: sys/arch/evbarm/dev/plcomvar.h
===================================================================
RCS file: /cvsroot/src/sys/arch/evbarm/dev/plcomvar.h,v
retrieving revision 1.11
diff -u -p -u -r1.11 plcomvar.h
--- sys/arch/evbarm/dev/plcomvar.h	25 Jul 2012 07:26:18 -0000	1.11
+++ sys/arch/evbarm/dev/plcomvar.h	11 Aug 2012 08:58:25 -0000
@@ -112,7 +112,8 @@ struct plcom_softc {
 
 	int sc_hwflags,
 	    sc_swflags;
-	u_int sc_fifolen;
+	u_int sc_fifolen,
+	       sc_fifotrigger;
 
 	u_int sc_r_hiwat,
 	      sc_r_lowat;