diff --git a/sys/dev/rtwn/if_rtwnvar.h b/sys/dev/rtwn/if_rtwnvar.h
--- a/sys/dev/rtwn/if_rtwnvar.h
+++ b/sys/dev/rtwn/if_rtwnvar.h
@@ -408,6 +408,7 @@
 
 	uint16_t			bcn_status_reg[RTWN_PORT_COUNT];
 	uint32_t			rcr;	/* Rx filter */
+	uint8_t				chan_flag;
 };
 MALLOC_DECLARE(M_RTWN_PRIV);
 
diff --git a/sys/dev/rtwn/rtl8188e/r88e_reg.h b/sys/dev/rtwn/rtl8188e/r88e_reg.h
--- a/sys/dev/rtwn/rtl8188e/r88e_reg.h
+++ b/sys/dev/rtwn/rtl8188e/r88e_reg.h
@@ -121,5 +121,6 @@
 
 /* Bits for R88E_XCK_OUT_CTRL. */
 #define R88E_XCK_OUT_CTRL_EN	1
+#define R88E_USB_DELAY_US_DEF	1000
 
 #endif	/* R88E_REG_H */
diff --git a/sys/dev/rtwn/rtl8188e/usb/r88eu_attach.c b/sys/dev/rtwn/rtl8188e/usb/r88eu_attach.c
--- a/sys/dev/rtwn/rtl8188e/usb/r88eu_attach.c
+++ b/sys/dev/rtwn/rtl8188e/usb/r88eu_attach.c
@@ -58,6 +58,7 @@
 #include <dev/rtwn/rtl8188e/r88e_rom_image.h>	/* for 'macaddr' field */
 
 #include <dev/rtwn/rtl8188e/usb/r88eu.h>
+#include <dev/rtwn/rtl8188e/r88e_reg.h>
 
 static struct rtwn_r88e_txpwr r88e_txpwr;
 
@@ -122,6 +123,7 @@
 	/* USB part. */
 	uc->uc_align_rx			= r92cu_align_rx;
 	uc->tx_agg_desc_num		= 6;
+	uc->uc_delay_us			= R88E_USB_DELAY_US_DEF;
 
 	/* Common part. */
 	sc->sc_flags			= RTWN_FLAG_EXT_HDR;
diff --git a/sys/dev/rtwn/rtl8188e/usb/r88eu_init.c b/sys/dev/rtwn/rtl8188e/usb/r88eu_init.c
--- a/sys/dev/rtwn/rtl8188e/usb/r88eu_init.c
+++ b/sys/dev/rtwn/rtl8188e/usb/r88eu_init.c
@@ -48,6 +48,8 @@
 #include <dev/rtwn/rtl8192c/r92c.h>
 #include <dev/rtwn/rtl8192c/r92c_var.h>
 
+#include <dev/rtwn/usb/rtwn_usb_var.h>
+
 #include <dev/rtwn/rtl8188e/usb/r88eu.h>
 #include <dev/rtwn/rtl8188e/usb/r88eu_reg.h>
 
@@ -76,8 +78,12 @@
 	if (res != 0)		\
 		return (EIO);	\
 } while(0)
+	struct rtwn_usb_softc *uc;
 	int ntries;
 
+	if ((uc = RTWN_USB_SOFTC(sc)) != NULL)
+		uc->uc_write_delay = 1;
+
 	/* Wait for power ready bit. */
 	for (ntries = 0; ntries < 5000; ntries++) {
 		if (rtwn_read_4(sc, R92C_APS_FSMCO) & R92C_APS_FSMCO_SUS_HOST)
@@ -85,6 +91,8 @@
 		rtwn_delay(sc, 10);
 	}
 	if (ntries == 5000) {
+		if (uc != NULL)
+			uc->uc_write_delay = 0;
 		device_printf(sc->sc_dev,
 		    "timeout waiting for chip power up\n");
 		return (ETIMEDOUT);
@@ -112,8 +120,11 @@
 			break;
 		rtwn_delay(sc, 10);
 	}
-	if (ntries == 5000)
+	if (ntries == 5000) {
+		if (uc != NULL)
+			uc->uc_write_delay = 0;
 		return (ETIMEDOUT);
+	}
 
 	/* Enable LDO normal mode. */
 	RTWN_CHK(rtwn_setbits_1(sc, R92C_LPLDO_CTRL,
@@ -128,6 +139,8 @@
 	    ((sc->sc_hwcrypto != RTWN_CRYPTO_SW) ? R92C_CR_ENSEC : 0) |
 	    R92C_CR_CALTMR_EN));
 
+	if (uc != NULL)
+		uc->uc_write_delay = 0;
 	return (0);
 #undef RTWN_CHK
 }
diff --git a/sys/dev/rtwn/rtl8192c/r92c_chan.c b/sys/dev/rtwn/rtl8192c/r92c_chan.c
--- a/sys/dev/rtwn/rtl8192c/r92c_chan.c
+++ b/sys/dev/rtwn/rtl8192c/r92c_chan.c
@@ -364,6 +364,7 @@
 	u_int chan;
 	int i;
 
+	sc->chan_flag = 1;
 	chan = rtwn_chan2centieee(c);
 
 	/* Set Tx power for this new channel. */
@@ -377,6 +378,8 @@
 		r92c_set_bw40(sc, chan, IEEE80211_IS_CHAN_HT40U(c));
 	else
 		rtwn_r92c_set_bw20(sc, chan);
+
+	sc->chan_flag = 0;
 }
 
 void
diff --git a/sys/dev/rtwn/rtl8192c/r92c_reg.h b/sys/dev/rtwn/rtl8192c/r92c_reg.h
--- a/sys/dev/rtwn/rtl8192c/r92c_reg.h
+++ b/sys/dev/rtwn/rtl8192c/r92c_reg.h
@@ -926,4 +926,6 @@
 #define R92C_RF_T_METER_VAL_M	0x1f
 #define R92C_RF_T_METER_VAL_S	0
 
+#define R92C_USB_DELAY_US_DEF	1000
+
 #endif	/* R92C_REG_H */
diff --git a/sys/dev/rtwn/rtl8192c/usb/r92cu_attach.c b/sys/dev/rtwn/rtl8192c/usb/r92cu_attach.c
--- a/sys/dev/rtwn/rtl8192c/usb/r92cu_attach.c
+++ b/sys/dev/rtwn/rtl8192c/usb/r92cu_attach.c
@@ -151,6 +151,7 @@
 	/* USB part. */
 	uc->uc_align_rx			= r92cu_align_rx;
 	uc->tx_agg_desc_num		= 6;
+	uc->uc_delay_us			= R92C_USB_DELAY_US_DEF;
 
 	/* Common part. */
 	sc->sc_flags			= RTWN_FLAG_CAM_FIXED;
diff --git a/sys/dev/rtwn/rtl8192e/r92e_chan.c b/sys/dev/rtwn/rtl8192e/r92e_chan.c
--- a/sys/dev/rtwn/rtl8192e/r92e_chan.c
+++ b/sys/dev/rtwn/rtl8192e/r92e_chan.c
@@ -238,6 +238,7 @@
 	u_int chan;
 	int i;
 
+	sc->chan_flag = 1;
 	chan = rtwn_chan2centieee(c);
 
 	for (i = 0; i < sc->nrxchains; i++) {
@@ -252,4 +253,5 @@
 
 	/* Set Tx power for this new channel. */
 	r92e_set_txpower(sc, c);
+	sc->chan_flag = 0;
 }
diff --git a/sys/dev/rtwn/rtl8192e/r92e_init.c b/sys/dev/rtwn/rtl8192e/r92e_init.c
--- a/sys/dev/rtwn/rtl8192e/r92e_init.c
+++ b/sys/dev/rtwn/rtl8192e/r92e_init.c
@@ -53,6 +53,8 @@
 
 #include <dev/rtwn/if_rtwn_debug.h>
 
+#include <dev/rtwn/usb/rtwn_usb_var.h>
+
 #include <dev/rtwn/rtl8192c/r92c.h>
 
 #include <dev/rtwn/rtl8192e/r92e.h>
@@ -224,8 +226,12 @@
 	if (res != 0)		\
 		return (EIO);	\
 } while(0)
+	struct rtwn_usb_softc *uc;
 	int ntries;
 
+	if ((uc = RTWN_USB_SOFTC(sc)) != NULL)
+		uc->uc_write_delay = 1;
+
 	if (rtwn_read_4(sc, R92C_SYS_CFG) & R92C_SYS_CFG_TRP_BT_EN)
 		RTWN_CHK(rtwn_write_1(sc, R92C_LDO_SWR_CTRL, 0xc3));
 	else {
@@ -252,6 +258,8 @@
 		rtwn_delay(sc, 10);
 	}
 	if (ntries == 5000) {
+		if (uc != NULL)
+			uc->uc_write_delay = 0;
 		device_printf(sc->sc_dev,
 		    "timeout waiting for chip power up\n");
 		return (ETIMEDOUT);
@@ -269,8 +277,11 @@
 			break;
 		rtwn_delay(sc, 10);
 	}
-	if (ntries == 5000)
+	if (ntries == 5000) {
+		if (uc != NULL)
+			uc->uc_write_delay = 0;
 		return (ETIMEDOUT);
+	}
 
 	/* Enable MAC DMA/WMAC/SCHEDULE/SEC blocks. */
 	RTWN_CHK(rtwn_write_2(sc, R92C_CR, 0));
@@ -281,18 +292,27 @@
 	    ((sc->sc_hwcrypto != RTWN_CRYPTO_SW) ? R92C_CR_ENSEC : 0) |
 	    R92C_CR_CALTMR_EN));
 
+	if (uc != NULL)
+		uc->uc_write_delay = 0;
 	return (0);
 }
 
 void
 r92e_power_off(struct rtwn_softc *sc)
 {
+	struct rtwn_usb_softc *uc;
 	int error, ntries;
 
+	if ((uc = RTWN_USB_SOFTC(sc)) != NULL)
+		uc->uc_write_delay = 1;
+
 	/* Stop Rx. */
 	error = rtwn_write_1(sc, R92C_CR, 0);
-	if (error == ENXIO)	/* hardware gone */
+	if (error == ENXIO) {	/* hardware gone */
+		if (uc != NULL)
+			uc->uc_write_delay = 0;
 		return;
+	}
 
 	/* Move card to Low Power state. */
 	/* Block all Tx queues. */
@@ -306,6 +326,8 @@
 		rtwn_delay(sc, 10);
 	}
 	if (ntries == 5000) {
+		if (uc != NULL)
+			uc->uc_write_delay = 0;
 		device_printf(sc->sc_dev, "%s: failed to block Tx queues\n",
 		    __func__);
 		return;
@@ -363,6 +385,8 @@
 		rtwn_delay(sc, 10);
 	}
 	if (ntries == 5000) {
+		if (uc != NULL)
+			uc->uc_write_delay = 0;
 		device_printf(sc->sc_dev, "%s: could not turn off MAC\n",
 		    __func__);
 		return;
@@ -385,4 +409,7 @@
 	/* Enable SW LPS. */
 	rtwn_setbits_1_shift(sc, R92C_APS_FSMCO, 0,
 	    R92C_APS_FSMCO_APFM_RSM, 1);
+
+	if (uc != NULL)
+		uc->uc_write_delay = 0;
 }
diff --git a/sys/dev/rtwn/rtl8192e/r92e_reg.h b/sys/dev/rtwn/rtl8192e/r92e_reg.h
--- a/sys/dev/rtwn/rtl8192e/r92e_reg.h
+++ b/sys/dev/rtwn/rtl8192e/r92e_reg.h
@@ -41,5 +41,6 @@
 /* Bits for R92E_AFE_XTAL_CTRL. */
 #define R92E_AFE_XTAL_CTRL_ADDR_M	0x00fff000
 #define R92E_AFE_XTAL_CTRL_ADDR_S	12
+#define R92E_USB_DELAY_US_DEF		1000
 
 #endif	/* R92E_REG_H */
diff --git a/sys/dev/rtwn/rtl8192e/usb/r92eu_attach.c b/sys/dev/rtwn/rtl8192e/usb/r92eu_attach.c
--- a/sys/dev/rtwn/rtl8192e/usb/r92eu_attach.c
+++ b/sys/dev/rtwn/rtl8192e/usb/r92eu_attach.c
@@ -100,6 +100,7 @@
 	/* USB part. */
 	uc->uc_align_rx			= r12au_align_rx;
 	uc->tx_agg_desc_num		= 3;
+	uc->uc_delay_us			= R92E_USB_DELAY_US_DEF;
 
 	/* Common part. */
 	sc->sc_flags			= RTWN_FLAG_EXT_HDR;
diff --git a/sys/dev/rtwn/usb/rtwn_usb_attach.c b/sys/dev/rtwn/usb/rtwn_usb_attach.c
--- a/sys/dev/rtwn/usb/rtwn_usb_attach.c
+++ b/sys/dev/rtwn/usb/rtwn_usb_attach.c
@@ -377,6 +377,11 @@
 		uc->uc_rx_buf_size = RTWN_USB_RXBUFSZ_MIN;
 	if (uc->uc_rx_buf_size > RTWN_USB_RXBUFSZ_MAX)
 		uc->uc_rx_buf_size = RTWN_USB_RXBUFSZ_MAX;
+
+	uc->uc_delay_us = RTWN_USB_DELAY_US_DEF;
+	SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(tree), OID_AUTO,
+	    "delay_us", CTLFLAG_RWTUN, &uc->uc_delay_us,
+	    uc->uc_delay_us, "RTWN USB set channel delay microseconds");
 }
 
 static int
@@ -419,6 +424,7 @@
 	if (error != 0)
 		goto detach;
 
+	sc->chan_flag = 0;
 	return (0);
 
 detach:
diff --git a/sys/dev/rtwn/usb/rtwn_usb_reg.c b/sys/dev/rtwn/usb/rtwn_usb_reg.c
--- a/sys/dev/rtwn/usb/rtwn_usb_reg.c
+++ b/sys/dev/rtwn/usb/rtwn_usb_reg.c
@@ -88,12 +88,16 @@
     int len)
 {
 	usb_device_request_t req;
+	struct rtwn_usb_softc *uc;
 
 	req.bmRequestType = UT_WRITE_VENDOR_DEVICE;
 	req.bRequest = R92C_REQ_REGS;
 	USETW(req.wValue, addr);
 	USETW(req.wIndex, 0);
 	USETW(req.wLength, len);
+	uc = RTWN_USB_SOFTC(sc);
+	if (uc->uc_write_delay == 1 || sc->chan_flag == 1)
+		rtwn_delay(sc,uc->uc_delay_us);
 	return (rtwn_do_request(sc, &req, buf));
 }
 
diff --git a/sys/dev/rtwn/usb/rtwn_usb_var.h b/sys/dev/rtwn/usb/rtwn_usb_var.h
--- a/sys/dev/rtwn/usb/rtwn_usb_var.h
+++ b/sys/dev/rtwn/usb/rtwn_usb_var.h
@@ -27,6 +27,7 @@
 #define RTWN_USB_RXBUFSZ_DEF		(24)
 #define RTWN_USB_RXBUFSZ_MAX		(64)
 #define RTWN_USB_TXBUFSZ		(16 * 1024)
+#define RTWN_USB_DELAY_US_DEF		0
 
 #define RTWN_IFACE_INDEX		0
 
@@ -82,6 +83,9 @@
 	int			tx_agg_desc_num;
 
 	uint8_t			wme2qid[4];
+
+	int			uc_delay_us;
+	int			uc_write_delay;
 };
 #define RTWN_USB_SOFTC(sc)	((struct rtwn_usb_softc *)(sc))