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
@@ -122,6 +122,7 @@
 	/* USB part. */
 	uc->uc_align_rx			= r92cu_align_rx;
 	uc->tx_agg_desc_num		= 6;
+	uc->uc_write_delay		= 1;
 
 	/* 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
@@ -50,6 +50,7 @@
 
 #include <dev/rtwn/rtl8188e/usb/r88eu.h>
 #include <dev/rtwn/rtl8188e/usb/r88eu_reg.h>
+#include <dev/rtwn/usb/rtwn_usb_var.h>
 
 void
 r88eu_init_bb(struct rtwn_softc *sc)
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_write_delay		= 1;
 
 	/* Common part. */
 	sc->sc_flags			= RTWN_FLAG_CAM_FIXED;
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_write_delay		= 1;
 
 	/* 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 +377,10 @@
 		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;
+
+	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
@@ -390,6 +394,8 @@
 
 	device_set_usb_desc(self);
 	uc->uc_udev = uaa->device;
+	uc->uc_write_delay = 1;
+	uc->uc_delay_us = RTWN_USB_DELAY_US_DEF;
 	sc->sc_dev = self;
 	ic->ic_name = device_get_nameunit(self);
 
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->sc_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		1000
 
 #define RTWN_IFACE_INDEX		0
 
@@ -82,6 +83,8 @@
 	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))