Index: sys/dev/ichiic/ig4_iic.c
===================================================================
--- sys/dev/ichiic/ig4_iic.c
+++ sys/dev/ichiic/ig4_iic.c
@@ -49,6 +49,7 @@
 #include <sys/errno.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
+#include <sys/sx.h>
 #include <sys/syslog.h>
 #include <sys/bus.h>
 #include <sys/sysctl.h>
@@ -115,7 +116,7 @@
 			error = 0;
 			break;
 		}
-		mtx_sleep(sc, &sc->mutex, 0, "i2cslv", 1);
+		mtx_sleep(sc, &sc->ig4_io_lock, 0, "i2cslv", 1);
 	}
 	return (error);
 }
@@ -179,7 +180,7 @@
 		 * work, otherwise poll with the lock held.
 		 */
 		if (status & IG4_STATUS_RX_NOTEMPTY) {
-			mtx_sleep(sc, &sc->mutex, PZERO, "i2cwait",
+			mtx_sleep(sc, &sc->ig4_io_lock, PZERO, "i2cwait",
 				  (hz + 99) / 100); /* sleep up to 10ms */
 			count_us += 10000;
 		} else {
@@ -551,12 +552,12 @@
 	 */
 	reg_write(sc, IG4_REG_INTR_MASK, IG4_INTR_STOP_DET |
 					 IG4_INTR_RX_FULL);
-	mtx_lock(&sc->mutex);
+	mtx_lock(&sc->ig4_io_lock);
 	if (set_controller(sc, 0))
 		device_printf(sc->dev, "controller error during attach-1\n");
 	if (set_controller(sc, IG4_I2C_ENABLE))
 		device_printf(sc->dev, "controller error during attach-2\n");
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
 	error = bus_setup_intr(sc->dev, sc->intr_res, INTR_TYPE_MISC | INTR_MPSAFE,
 			       NULL, ig4iic_intr, sc, &sc->intr_handle);
 	if (error) {
@@ -615,7 +616,8 @@
 	if (sc->intr_handle)
 		bus_teardown_intr(sc->dev, sc->intr_res, sc->intr_handle);
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	sc->smb = NULL;
 	sc->intr_handle = NULL;
@@ -623,7 +625,8 @@
 	reg_read(sc, IG4_REG_CLR_INTR);
 	set_controller(sc, 0);
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (0);
 }
 
@@ -633,7 +636,8 @@
 	ig4iic_softc_t *sc = device_get_softc(dev);
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	switch (index) {
 	case SMB_REQUEST_BUS:
@@ -647,8 +651,8 @@
 		break;
 	}
 
-	mtx_unlock(&sc->mutex);
-
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -663,7 +667,8 @@
 	ig4iic_softc_t *sc = device_get_softc(dev);
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	switch (how) {
 	case SMB_QREAD:
@@ -676,8 +681,9 @@
 		error = SMB_ENOTSUPP;
 		break;
 	}
-	mtx_unlock(&sc->mutex);
 
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -695,7 +701,8 @@
 	uint32_t cmd;
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	cmd = byte;
@@ -706,7 +713,8 @@
 		error = SMB_ETIMEOUT;
 	}
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -721,7 +729,8 @@
 	ig4iic_softc_t *sc = device_get_softc(dev);
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	reg_write(sc, IG4_REG_DATA_CMD, IG4_DATA_COMMAND_RD);
@@ -733,7 +742,8 @@
 		error = SMB_ETIMEOUT;
 	}
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -746,13 +756,15 @@
 	ig4iic_softc_t *sc = device_get_softc(dev);
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	error = smb_transaction(sc, cmd, SMB_TRANS_NOCNT,
 				&byte, 1, NULL, 0, NULL);
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -766,7 +778,8 @@
 	char buf[2];
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	buf[0] = word & 0xFF;
@@ -774,7 +787,8 @@
 	error = smb_transaction(sc, cmd, SMB_TRANS_NOCNT,
 				buf, 2, NULL, 0, NULL);
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -787,13 +801,15 @@
 	ig4iic_softc_t *sc = device_get_softc(dev);
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	error = smb_transaction(sc, cmd, SMB_TRANS_NOCNT,
 				NULL, 0, byte, 1, NULL);
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -807,7 +823,8 @@
 	char buf[2];
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	if ((error = smb_transaction(sc, cmd, SMB_TRANS_NOCNT,
@@ -815,7 +832,8 @@
 		*word = (u_char)buf[0] | ((u_char)buf[1] << 8);
 	}
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -831,7 +849,8 @@
 	char wbuf[2];
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	wbuf[0] = sdata & 0xFF;
@@ -841,7 +860,8 @@
 		*rdata = (u_char)rbuf[0] | ((u_char)rbuf[1] << 8);
 	}
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -852,13 +872,15 @@
 	ig4iic_softc_t *sc = device_get_softc(dev);
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	error = smb_transaction(sc, cmd, 0,
 				buf, wcount, NULL, 0, NULL);
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -870,14 +892,16 @@
 	int rcount = *countp_char;
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, 0);
 	error = smb_transaction(sc, cmd, 0,
 				NULL, 0, buf, rcount, &rcount);
 	*countp_char = rcount;
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -889,13 +913,15 @@
 	ig4iic_softc_t *sc = device_get_softc(dev);
 	int error;
 
-	mtx_lock(&sc->mutex);
+	sx_xlock(&sc->ig4_call_lock);
+	mtx_lock(&sc->ig4_io_lock);
 
 	set_slave_addr(sc, slave, op);
 	error = smb_transaction(sc, cmd, op,
 				wbuf, wcount, rbuf, rcount, actualp);
 
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
+	sx_xunlock(&sc->ig4_call_lock);
 	return (error);
 }
 
@@ -908,7 +934,7 @@
 	ig4iic_softc_t *sc = cookie;
 	uint32_t status;
 
-	mtx_lock(&sc->mutex);
+	mtx_lock(&sc->ig4_io_lock);
 /*	reg_write(sc, IG4_REG_INTR_MASK, IG4_INTR_STOP_DET);*/
 	status = reg_read(sc, IG4_REG_I2C_STA);
 	while (status & IG4_STATUS_RX_NOTEMPTY) {
@@ -919,7 +945,7 @@
 	}
 	reg_read(sc, IG4_REG_CLR_INTR);
 	wakeup(sc);
-	mtx_unlock(&sc->mutex);
+	mtx_unlock(&sc->ig4_io_lock);
 }
 
 #define REGDUMP(sc, reg)	\
Index: sys/dev/ichiic/ig4_pci.c
===================================================================
--- sys/dev/ichiic/ig4_pci.c
+++ sys/dev/ichiic/ig4_pci.c
@@ -49,6 +49,7 @@
 #include <sys/errno.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
+#include <sys/sx.h>
 #include <sys/syslog.h>
 #include <sys/bus.h>
 
@@ -94,7 +95,8 @@
 
 	bzero(sc, sizeof(*sc));
 
-	mtx_init(&sc->mutex, device_get_nameunit(dev), "ig4iic", MTX_DEF);
+	mtx_init(&sc->ig4_io_lock, "IG4 I/O lock", NULL, MTX_DEF);
+	sx_init(&sc->ig4_call_lock, "IG4 call lock");
 
 	sc->dev = dev;
 	sc->regs_rid = PCIR_BAR(0);
@@ -150,7 +152,10 @@
 				     sc->regs_rid, sc->regs_res);
 		sc->regs_res = NULL;
 	}
-	mtx_destroy(&sc->mutex);
+	if (mtx_initialized(&sc->ig4_io_lock)) {
+		mtx_destroy(&sc->ig4_io_lock);
+		sx_destroy(&sc->ig4_call_lock);
+	}
 
 	return (0);
 }
@@ -179,9 +184,9 @@
 };
 
 static driver_t ig4iic_pci_driver = {
-        "ig4iic",
-        ig4iic_pci_methods,
-        sizeof(struct ig4iic_softc)
+	"ig4iic",
+	ig4iic_pci_methods,
+	sizeof(struct ig4iic_softc)
 };
 
 static devclass_t ig4iic_pci_devclass;
Index: sys/dev/ichiic/ig4_var.h
===================================================================
--- sys/dev/ichiic/ig4_var.h
+++ sys/dev/ichiic/ig4_var.h
@@ -70,7 +70,8 @@
 	int		slave_valid : 1;
 	int		read_started : 1;
 	int		write_started : 1;
-	struct mtx	mutex;
+	struct mtx	ig4_io_lock;
+	struct sx	ig4_call_lock;
 };
 
 typedef struct ig4iic_softc ig4iic_softc_t;