Index: head/sys/dev/flash/mx25l.c
===================================================================
--- head/sys/dev/flash/mx25l.c
+++ head/sys/dev/flash/mx25l.c
@@ -56,6 +56,8 @@
 #define	FL_NONE			0x00
 #define	FL_ERASE_4K		0x01
 #define	FL_ERASE_32K		0x02
+#define	FL_ENABLE_4B_ADDR	0x04
+#define	FL_DISABLE_4B_ADDR	0x08
 
 /*
  * Define the sectorsize to be a smaller size rather than the flash
@@ -113,6 +115,7 @@
 	{ "mx25ll32",	0xc2, 0x2016, 64 * 1024, 64, FL_NONE },
 	{ "mx25ll64",	0xc2, 0x2017, 64 * 1024, 128, FL_NONE },
 	{ "mx25ll128",	0xc2, 0x2018, 64 * 1024, 256, FL_ERASE_4K | FL_ERASE_32K },
+	{ "mx25ll256",	0xc2, 0x2019, 64 * 1024, 512, FL_ERASE_4K | FL_ERASE_32K | FL_ENABLE_4B_ADDR },
 	{ "s25fl032",	0x01, 0x0215, 64 * 1024, 64, FL_NONE },
 	{ "s25fl064",	0x01, 0x0216, 64 * 1024, 128, FL_NONE },
 	{ "s25fl128",	0x01, 0x2018, 64 * 1024, 256, FL_NONE },
@@ -219,10 +222,13 @@
 static void
 mx25l_erase_cmd(device_t dev, off_t sector, uint8_t ecmd)
 {
-	uint8_t txBuf[4], rxBuf[4];
+	struct mx25l_softc *sc;
+	uint8_t txBuf[5], rxBuf[5];
 	struct spi_command cmd;
 	int err;
 
+	sc = device_get_softc(dev);
+
 	mx25l_wait_for_device_ready(dev);
 	mx25l_set_writable(dev, 1);
 
@@ -233,11 +239,20 @@
 	txBuf[0] = ecmd;
 	cmd.tx_cmd = txBuf;
 	cmd.rx_cmd = rxBuf;
-	cmd.rx_cmd_sz = 4;
-	cmd.tx_cmd_sz = 4;
-	txBuf[1] = ((sector >> 16) & 0xff);
-	txBuf[2] = ((sector >> 8) & 0xff);
-	txBuf[3] = (sector & 0xff);
+	if (sc->sc_flags & FL_ENABLE_4B_ADDR) {
+		cmd.rx_cmd_sz = 5;
+		cmd.tx_cmd_sz = 5;
+		txBuf[1] = ((sector >> 24) & 0xff);
+		txBuf[2] = ((sector >> 16) & 0xff);
+		txBuf[3] = ((sector >> 8) & 0xff);
+		txBuf[4] = (sector & 0xff);
+	} else {
+		cmd.rx_cmd_sz = 4;
+		cmd.tx_cmd_sz = 4;
+		txBuf[1] = ((sector >> 16) & 0xff);
+		txBuf[2] = ((sector >> 8) & 0xff);
+		txBuf[3] = (sector & 0xff);
+	}
 	err = SPIBUS_TRANSFER(device_get_parent(dev), dev, &cmd);
 }
 
@@ -255,8 +270,13 @@
 	pdev = device_get_parent(dev);
 	sc = device_get_softc(dev);
 
-	cmd.tx_cmd_sz = 4;
-	cmd.rx_cmd_sz = 4;
+	if (sc->sc_flags & FL_ENABLE_4B_ADDR) {
+		cmd.tx_cmd_sz = 5;
+		cmd.rx_cmd_sz = 5;
+	} else {
+		cmd.tx_cmd_sz = 4;
+		cmd.rx_cmd_sz = 4;
+	}
 
 	bytes_writen = 0;
 	write_offset = offset;
@@ -290,9 +310,16 @@
 			mx25l_erase_cmd(dev, offset + bytes_writen, CMD_SECTOR_ERASE);
 
 		txBuf[0] = CMD_PAGE_PROGRAM;
-		txBuf[1] = ((write_offset >> 16) & 0xff);
-		txBuf[2] = ((write_offset >> 8) & 0xff);
-		txBuf[3] = (write_offset & 0xff);
+		if (sc->sc_flags & FL_ENABLE_4B_ADDR) {
+			txBuf[1] = ((write_offset >> 24) & 0xff);
+			txBuf[2] = ((write_offset >> 16) & 0xff);
+			txBuf[3] = ((write_offset >> 8) & 0xff);
+			txBuf[4] = (write_offset & 0xff);
+		} else {
+			txBuf[1] = ((write_offset >> 16) & 0xff);
+			txBuf[2] = ((write_offset >> 8) & 0xff);
+			txBuf[3] = (write_offset & 0xff);
+		}
 
 		bytes_to_write = MIN(FLASH_PAGE_SIZE,
 		    count - bytes_writen);
@@ -344,14 +371,26 @@
 		return (EIO);
 
 	txBuf[0] = CMD_FAST_READ;
-	cmd.tx_cmd_sz = 5;
-	cmd.rx_cmd_sz = 5;
-
-	txBuf[1] = ((offset >> 16) & 0xff);
-	txBuf[2] = ((offset >> 8) & 0xff);
-	txBuf[3] = (offset & 0xff);
-	/* Dummy byte */
-	txBuf[4] = 0;
+	if (sc->sc_flags & FL_ENABLE_4B_ADDR) {
+		cmd.tx_cmd_sz = 6;
+		cmd.rx_cmd_sz = 6;
+
+		txBuf[1] = ((offset >> 24) & 0xff);
+		txBuf[2] = ((offset >> 16) & 0xff);
+		txBuf[3] = ((offset >> 8) & 0xff);
+		txBuf[4] = (offset & 0xff);
+		/* Dummy byte */
+		txBuf[5] = 0;
+	} else {
+		cmd.tx_cmd_sz = 5;
+		cmd.rx_cmd_sz = 5;
+
+		txBuf[1] = ((offset >> 16) & 0xff);
+		txBuf[2] = ((offset >> 8) & 0xff);
+		txBuf[3] = (offset & 0xff);
+		/* Dummy byte */
+		txBuf[4] = 0;
+	}
 
 	cmd.tx_cmd = txBuf;
 	cmd.rx_cmd = rxBuf;
@@ -366,6 +405,34 @@
 }
 
 static int
+mx25l_set_4b_mode(device_t dev, uint8_t command)
+{
+	uint8_t txBuf[1], rxBuf[1];
+	struct spi_command cmd;
+	device_t pdev;
+	int err;
+
+	memset(&cmd, 0, sizeof(cmd));
+	memset(txBuf, 0, sizeof(txBuf));
+	memset(rxBuf, 0, sizeof(rxBuf));
+
+	pdev = device_get_parent(dev);
+
+	cmd.tx_cmd_sz = cmd.rx_cmd_sz = 1;
+
+	cmd.tx_cmd = txBuf;
+	cmd.rx_cmd = rxBuf;
+
+	txBuf[0] = command;
+
+	err = SPIBUS_TRANSFER(pdev, dev, &cmd);
+
+	mx25l_wait_for_device_ready(dev);
+
+	return (err);
+}
+
+static int
 mx25l_probe(device_t dev)
 {
 
@@ -413,6 +480,12 @@
 	sc->sc_sectorsize =  ident->sectorsize;
 	sc->sc_flags = ident->flags;
 
+	if (sc->sc_flags & FL_ENABLE_4B_ADDR)
+		mx25l_set_4b_mode(dev, CMD_ENTER_4B_MODE);
+
+	if (sc->sc_flags & FL_DISABLE_4B_ADDR)
+		mx25l_set_4b_mode(dev, CMD_EXIT_4B_MODE);
+
         /* NB: use stripesize to hold the erase/region size for RedBoot */
 	sc->sc_disk->d_stripesize = ident->sectorsize;
 
Index: head/sys/dev/flash/mx25lreg.h
===================================================================
--- head/sys/dev/flash/mx25lreg.h
+++ head/sys/dev/flash/mx25lreg.h
@@ -45,6 +45,8 @@
 #define CMD_BULK_ERASE		0xC7
 #define	CMD_BLOCK_4K_ERASE	0x20
 #define	CMD_BLOCK_32K_ERASE	0x52
+#define	CMD_ENTER_4B_MODE	0xB7
+#define	CMD_EXIT_4B_MODE	0xE9
 
 /*
  * Status register flags