diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 1dbc185..ea5c28d 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -942,6 +942,40 @@ u32 mmc_select_voltage(struct mmc_host *host, u32 ocr)
 	return ocr;
 }
 
+int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage)
+{
+	struct mmc_command cmd;
+	int err = 0;
+
+	BUG_ON(!host);
+
+	/*
+	 * Send CMD11 only if the request is to switch the card to
+	 * 1.8V signalling.
+	 */
+	if (signal_voltage == MMC_SIGNAL_VOLTAGE_180) {
+		memset(&cmd, 0, sizeof(struct mmc_command));
+
+		cmd.opcode = SD_SWITCH_VOLTAGE;
+		cmd.arg = 0;
+		cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
+
+		err = mmc_wait_for_cmd(host, &cmd, 0);
+		if (err)
+			return err;
+
+		if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR))
+			return -EIO;
+	}
+
+	host->ios.signal_voltage = signal_voltage;
+
+	if (host->ops->start_signal_voltage_switch)
+		err = host->ops->start_signal_voltage_switch(host, &host->ios);
+
+	return err;
+}
+
 /*
  * Select timing parameters for host.
  */
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index ca1fdde..7745dea 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -41,6 +41,7 @@ void mmc_set_bus_width(struct mmc_host *host, unsigned int width);
 void mmc_set_bus_width_ddr(struct mmc_host *host, unsigned int width,
 			   unsigned int ddr);
 u32 mmc_select_voltage(struct mmc_host *host, u32 ocr);
+int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage);
 void mmc_set_timing(struct mmc_host *host, unsigned int timing);
 
 static inline void mmc_delay(unsigned int ms)
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 6dac89f..b0cd285 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -403,6 +403,7 @@ struct device_type sd_type = {
 int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid)
 {
 	int err;
+	u32 rocr;
 
 	/*
 	 * Since we're changing the OCR value, we seem to
@@ -420,12 +421,38 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid)
 	 */
 	err = mmc_send_if_cond(host, ocr);
 	if (!err)
-		ocr |= 1 << 30;
+		ocr |= SD_OCR_CCS;
 
-	err = mmc_send_app_op_cond(host, ocr, NULL);
+	/*
+	 * If the host supports one of UHS-I modes, request the card
+	 * to switch to 1.8V signaling level.
+	 */
+	if (host->caps & (MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 |
+	    MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 | MMC_CAP_UHS_DDR50))
+		ocr |= SD_OCR_S18R;
+
+	/* If the host can supply more than 150mA, XPC should be set to 1. */
+	if (host->caps & (MMC_CAP_SET_XPC_330 | MMC_CAP_SET_XPC_300 |
+	    MMC_CAP_SET_XPC_180))
+		ocr |= SD_OCR_XPC;
+
+try_again:
+	err = mmc_send_app_op_cond(host, ocr, &rocr);
 	if (err)
 		return err;
 
+	/*
+	 * In case CCS and S18A in the response is set, start Signal Voltage
+	 * Switch procedure. SPI mode doesn't support CMD11.
+	 */
+	if (!mmc_host_is_spi(host) && ((rocr & 0x41000000) == 0x41000000)) {
+		err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180);
+		if (err) {
+			ocr &= ~SD_OCR_S18R;
+			goto try_again;
+		}
+	}
+
 	if (mmc_host_is_spi(host))
 		err = mmc_send_cid(host, cid);
 	else
@@ -773,6 +800,11 @@ int mmc_attach_sd(struct mmc_host *host)
 	BUG_ON(!host);
 	WARN_ON(!host->claimed);
 
+	/* Make sure we are at 3.3V signalling voltage */
+	err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_330);
+	if (err)
+		return err;
+
 	err = mmc_send_app_op_cond(host, 0, &ocr);
 	if (err)
 		return err;
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index e5cfe70..52faa50 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -83,6 +83,8 @@ static void sdhci_dumpregs(struct sdhci_host *host)
 	printk(KERN_DEBUG DRIVER_NAME ": Cmd:      0x%08x | Max curr: 0x%08x\n",
 		sdhci_readw(host, SDHCI_COMMAND),
 		sdhci_readl(host, SDHCI_MAX_CURRENT));
+	printk(KERN_DEBUG DRIVER_NAME ": Host ctl2: 0x%08x\n",
+		sdhci_readw(host, SDHCI_HOST_CONTROL2));
 
 	if (host->flags & SDHCI_USE_ADMA)
 		printk(KERN_DEBUG DRIVER_NAME ": ADMA Err: 0x%08x | ADMA Ptr: 0x%08x\n",
@@ -1323,11 +1325,115 @@ out:
 	spin_unlock_irqrestore(&host->lock, flags);
 }
 
+static int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
+	struct mmc_ios *ios)
+{
+	struct sdhci_host *host;
+	u8 pwr;
+	u16 clk, ctrl;
+	u32 present_state;
+
+	host = mmc_priv(mmc);
+
+	/*
+	 * Signal Voltage Switching is only applicable for Host Controllers
+	 * v3.00 and above.
+	 */
+	if (host->version < SDHCI_SPEC_300)
+		return 0;
+
+	/*
+	 * We first check whether the request is to set signalling voltage
+	 * to 3.3V. If so, we change the voltage to 3.3V and return quickly.
+	 */
+	ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+	if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_330) {
+		/* Set 1.8V Signal Enable in the Host Control2 register to 0 */
+		ctrl &= ~SDHCI_CTRL_VDD_180;
+		sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
+
+		/* Wait for 5ms */
+		usleep_range(5000, 5500);
+
+		/* 3.3V regulator output should be stable within 5 ms */
+		ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+		if (!(ctrl & SDHCI_CTRL_VDD_180))
+			return 0;
+		else {
+			printk(KERN_INFO DRIVER_NAME ": Switching to 3.3V "
+				"signalling voltage failed\n");
+			return -EIO;
+		}
+	} else if (!(ctrl & SDHCI_CTRL_VDD_180) &&
+		  (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_180)) {
+		/* Stop SDCLK */
+		clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+		clk &= ~SDHCI_CLOCK_CARD_EN;
+		sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
+
+		/* Check whether DAT[3:0] is 0000 */
+		present_state = sdhci_readl(host, SDHCI_PRESENT_STATE);
+		if (!((present_state & SDHCI_DATA_LVL_MASK) >>
+		       SDHCI_DATA_LVL_SHIFT)) {
+			/*
+			 * Enable 1.8V Signal Enable in the Host Control2
+			 * register
+			 */
+			ctrl |= SDHCI_CTRL_VDD_180;
+			sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
+
+			/* Wait for 5ms */
+			usleep_range(5000, 5500);
+
+			ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+			if (ctrl & SDHCI_CTRL_VDD_180) {
+				/* Provide SDCLK again and wait for 1ms*/
+				clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+				clk |= SDHCI_CLOCK_CARD_EN;
+				sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
+				usleep_range(1000, 1500);
+
+				/*
+				 * If DAT[3:0] level is 1111b, then the card
+				 * was successfully switched to 1.8V signaling.
+				 */
+				present_state = sdhci_readl(host,
+							SDHCI_PRESENT_STATE);
+				if ((present_state & SDHCI_DATA_LVL_MASK) ==
+				     SDHCI_DATA_LVL_MASK) {
+					return 0;
+				}
+			}
+		}
+
+		/*
+		 * If we are here, that means the switch to 1.8V signaling
+		 * failed. We power cycle the card, and retry initialization
+		 * sequence by setting S18R to 0.
+		 */
+		pwr = sdhci_readb(host, SDHCI_POWER_CONTROL);
+		pwr &= ~SDHCI_POWER_ON;
+		sdhci_writeb(host, pwr, SDHCI_POWER_CONTROL);
+
+		/* Wait for 1ms as per the spec */
+		usleep_range(1000, 1500);
+		pwr |= SDHCI_POWER_ON;
+		sdhci_writeb(host, pwr, SDHCI_POWER_CONTROL);
+
+		printk(KERN_INFO DRIVER_NAME ": Switching to 1.8V signalling "
+			"voltage failed, retrying with S18R set to 0\n");
+		return -EAGAIN;
+	} else
+		/* No signal voltage switch required */
+		return 0;
+}
+
 static const struct mmc_host_ops sdhci_ops = {
 	.request	= sdhci_request,
 	.set_ios	= sdhci_set_ios,
 	.get_ro		= sdhci_get_ro,
 	.enable_sdio_irq = sdhci_enable_sdio_irq,
+	.start_signal_voltage_switch	= sdhci_start_signal_voltage_switch,
 };
 
 /*****************************************************************************\
@@ -1808,7 +1914,9 @@ EXPORT_SYMBOL_GPL(sdhci_alloc_host);
 int sdhci_add_host(struct sdhci_host *host)
 {
 	struct mmc_host *mmc;
-	unsigned int caps, ocr_avail;
+	u32 caps[2];
+	u32 max_current_caps;
+	unsigned int ocr_avail;
 	int ret;
 
 	WARN_ON(host == NULL);
@@ -1831,12 +1939,15 @@ int sdhci_add_host(struct sdhci_host *host)
 			host->version);
 	}
 
-	caps = (host->quirks & SDHCI_QUIRK_MISSING_CAPS) ? host->caps :
+	caps[0] = (host->quirks & SDHCI_QUIRK_MISSING_CAPS) ? host->caps :
 		sdhci_readl(host, SDHCI_CAPABILITIES);
 
+	caps[1] = (host->version >= SDHCI_SPEC_300) ?
+		sdhci_readl(host, SDHCI_CAPABILITIES_1) : 0;
+
 	if (host->quirks & SDHCI_QUIRK_FORCE_DMA)
 		host->flags |= SDHCI_USE_SDMA;
-	else if (!(caps & SDHCI_CAN_DO_SDMA))
+	else if (!(caps[0] & SDHCI_CAN_DO_SDMA))
 		DBG("Controller doesn't have SDMA capability\n");
 	else
 		host->flags |= SDHCI_USE_SDMA;
@@ -1847,7 +1958,8 @@ int sdhci_add_host(struct sdhci_host *host)
 		host->flags &= ~SDHCI_USE_SDMA;
 	}
 
-	if ((host->version >= SDHCI_SPEC_200) && (caps & SDHCI_CAN_DO_ADMA2))
+	if ((host->version >= SDHCI_SPEC_200) &&
+		(caps[0] & SDHCI_CAN_DO_ADMA2))
 		host->flags |= SDHCI_USE_ADMA;
 
 	if ((host->quirks & SDHCI_QUIRK_BROKEN_ADMA) &&
@@ -1897,10 +2009,10 @@ int sdhci_add_host(struct sdhci_host *host)
 	}
 
 	if (host->version >= SDHCI_SPEC_300)
-		host->max_clk = (caps & SDHCI_CLOCK_V3_BASE_MASK)
+		host->max_clk = (caps[0] & SDHCI_CLOCK_V3_BASE_MASK)
 			>> SDHCI_CLOCK_BASE_SHIFT;
 	else
-		host->max_clk = (caps & SDHCI_CLOCK_BASE_MASK)
+		host->max_clk = (caps[0] & SDHCI_CLOCK_BASE_MASK)
 			>> SDHCI_CLOCK_BASE_SHIFT;
 
 	host->max_clk *= 1000000;
@@ -1916,7 +2028,7 @@ int sdhci_add_host(struct sdhci_host *host)
 	}
 
 	host->timeout_clk =
-		(caps & SDHCI_TIMEOUT_CLK_MASK) >> SDHCI_TIMEOUT_CLK_SHIFT;
+		(caps[0] & SDHCI_TIMEOUT_CLK_MASK) >> SDHCI_TIMEOUT_CLK_SHIFT;
 	if (host->timeout_clk == 0) {
 		if (host->ops->get_timeout_clock) {
 			host->timeout_clk = host->ops->get_timeout_clock(host);
@@ -1928,7 +2040,7 @@ int sdhci_add_host(struct sdhci_host *host)
 			return -ENODEV;
 		}
 	}
-	if (caps & SDHCI_TIMEOUT_CLK_UNIT)
+	if (caps[0] & SDHCI_TIMEOUT_CLK_UNIT)
 		host->timeout_clk *= 1000;
 
 	/*
@@ -1955,21 +2067,76 @@ int sdhci_add_host(struct sdhci_host *host)
 	if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA))
 		mmc->caps |= MMC_CAP_4_BIT_DATA;
 
-	if (caps & SDHCI_CAN_DO_HISPD)
+	if (caps[0] & SDHCI_CAN_DO_HISPD)
 		mmc->caps |= MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED;
 
 	if ((host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION) &&
 	    mmc_card_is_removable(mmc))
 		mmc->caps |= MMC_CAP_NEEDS_POLL;
 
+	/* UHS-I mode(s) supported by the host controller. */
+	if (host->version >= SDHCI_SPEC_300)
+		mmc->caps |= MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25;
+
+	/* SDR104 supports also implies SDR50 support */
+	if (caps[1] & SDHCI_SUPPORT_SDR104)
+		mmc->caps |= MMC_CAP_UHS_SDR104 | MMC_CAP_UHS_SDR50;
+	else if (caps[1] & SDHCI_SUPPORT_SDR50)
+		mmc->caps |= MMC_CAP_UHS_SDR50;
+
+	if (caps[1] & SDHCI_SUPPORT_DDR50)
+		mmc->caps |= MMC_CAP_UHS_DDR50;
+
 	ocr_avail = 0;
-	if (caps & SDHCI_CAN_VDD_330)
+	/*
+	 * According to SD Host Controller spec v3.00, if the Host System
+	 * can afford more than 150mA, Host Driver should set XPC to 1. Also
+	 * the value is meaningful only if Voltage Support in the Capabilities
+	 * register is set. The actual current value is 4 times the register
+	 * value.
+	 */
+	max_current_caps = sdhci_readl(host, SDHCI_MAX_CURRENT);
+
+	if (caps[0] & SDHCI_CAN_VDD_330) {
+		int max_current_330;
+
 		ocr_avail |= MMC_VDD_32_33 | MMC_VDD_33_34;
-	if (caps & SDHCI_CAN_VDD_300)
+
+		max_current_330 = ((max_current_caps &
+				   SDHCI_MAX_CURRENT_330_MASK) >>
+				   SDHCI_MAX_CURRENT_330_SHIFT) *
+				   SDHCI_MAX_CURRENT_MULTIPLIER;
+
+		if (max_current_330 > 150)
+			mmc->caps |= MMC_CAP_SET_XPC_330;
+	}
+	if (caps[0] & SDHCI_CAN_VDD_300) {
+		int max_current_300;
+
 		ocr_avail |= MMC_VDD_29_30 | MMC_VDD_30_31;
-	if (caps & SDHCI_CAN_VDD_180)
+
+		max_current_300 = ((max_current_caps &
+				   SDHCI_MAX_CURRENT_300_MASK) >>
+				   SDHCI_MAX_CURRENT_300_SHIFT) *
+				   SDHCI_MAX_CURRENT_MULTIPLIER;
+
+		if (max_current_300 > 150)
+			mmc->caps |= MMC_CAP_SET_XPC_300;
+	}
+	if (caps[0] & SDHCI_CAN_VDD_180) {
+		int max_current_180;
+
 		ocr_avail |= MMC_VDD_165_195;
 
+		max_current_180 = ((max_current_caps &
+				   SDHCI_MAX_CURRENT_180_MASK) >>
+				   SDHCI_MAX_CURRENT_180_SHIFT) *
+				   SDHCI_MAX_CURRENT_MULTIPLIER;
+
+		if (max_current_180 > 150)
+			mmc->caps |= MMC_CAP_SET_XPC_180;
+	}
+
 	mmc->ocr_avail = ocr_avail;
 	mmc->ocr_avail_sdio = ocr_avail;
 	if (host->ocr_avail_sdio)
@@ -2029,7 +2196,7 @@ int sdhci_add_host(struct sdhci_host *host)
 	if (host->quirks & SDHCI_QUIRK_FORCE_BLK_SZ_2048) {
 		mmc->max_blk_size = 2;
 	} else {
-		mmc->max_blk_size = (caps & SDHCI_MAX_BLOCK_MASK) >>
+		mmc->max_blk_size = (caps[0] & SDHCI_MAX_BLOCK_MASK) >>
 				SDHCI_MAX_BLOCK_SHIFT;
 		if (mmc->max_blk_size >= 3) {
 			printk(KERN_WARNING "%s: Invalid maximum block size, "
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index c6e25a7..5cba2fe 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -68,6 +68,8 @@
 #define  SDHCI_DATA_AVAILABLE	0x00000800
 #define  SDHCI_CARD_PRESENT	0x00010000
 #define  SDHCI_WRITE_PROTECT	0x00080000
+#define  SDHCI_DATA_LVL_MASK	0x00F00000
+#define   SDHCI_DATA_LVL_SHIFT	20
 
 #define SDHCI_HOST_CONTROL 	0x28
 #define  SDHCI_CTRL_LED		0x01
@@ -146,7 +148,8 @@
 
 #define SDHCI_ACMD12_ERR	0x3C
 
-/* 3E-3F reserved */
+#define SDHCI_HOST_CONTROL2		0x3E
+#define  SDHCI_CTRL_VDD_180		0x0008
 
 #define SDHCI_CAPABILITIES	0x40
 #define  SDHCI_TIMEOUT_CLK_MASK	0x0000003F
@@ -167,9 +170,20 @@
 #define  SDHCI_CAN_VDD_180	0x04000000
 #define  SDHCI_CAN_64BIT	0x10000000
 
+#define  SDHCI_SUPPORT_SDR50	0x00000001
+#define  SDHCI_SUPPORT_SDR104	0x00000002
+#define  SDHCI_SUPPORT_DDR50	0x00000004
+
 #define SDHCI_CAPABILITIES_1	0x44
 
-#define SDHCI_MAX_CURRENT	0x48
+#define SDHCI_MAX_CURRENT		0x48
+#define  SDHCI_MAX_CURRENT_330_MASK	0x0000FF
+#define  SDHCI_MAX_CURRENT_330_SHIFT	0
+#define  SDHCI_MAX_CURRENT_300_MASK	0x00FF00
+#define  SDHCI_MAX_CURRENT_300_SHIFT	8
+#define  SDHCI_MAX_CURRENT_180_MASK	0xFF0000
+#define  SDHCI_MAX_CURRENT_180_SHIFT	16
+#define   SDHCI_MAX_CURRENT_MULTIPLIER	4
 
 /* 4C-4F reserved for more max current */
 
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 0fffa5c..bde5a0b 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -56,6 +56,11 @@ struct mmc_ios {
 #define MMC_SDR_MODE		0
 #define MMC_1_2V_DDR_MODE	1
 #define MMC_1_8V_DDR_MODE	2
+
+	unsigned char	signal_voltage;		/* signalling voltage (1.8V or 3.3V) */
+
+#define MMC_SIGNAL_VOLTAGE_330	0
+#define MMC_SIGNAL_VOLTAGE_180	1
 };
 
 struct mmc_host_ops {
@@ -117,6 +122,8 @@ struct mmc_host_ops {
 
 	/* optional callback for HC quirks */
 	void	(*init_card)(struct mmc_host *host, struct mmc_card *card);
+
+	int	(*start_signal_voltage_switch)(struct mmc_host *host, struct mmc_ios *ios);
 };
 
 struct mmc_card;
@@ -173,6 +180,14 @@ struct mmc_host {
 						/* DDR mode at 1.2V */
 #define MMC_CAP_POWER_OFF_CARD	(1 << 13)	/* Can power off after boot */
 #define MMC_CAP_BUS_WIDTH_TEST	(1 << 14)	/* CMD14/CMD19 bus width ok */
+#define MMC_CAP_UHS_SDR12	(1 << 15)	/* Host supports UHS SDR12 mode */
+#define MMC_CAP_UHS_SDR25	(1 << 16)	/* Host supports UHS SDR25 mode */
+#define MMC_CAP_UHS_SDR50	(1 << 17)	/* Host supports UHS SDR50 mode */
+#define MMC_CAP_UHS_SDR104	(1 << 18)	/* Host supports UHS SDR104 mode */
+#define MMC_CAP_UHS_DDR50	(1 << 19)	/* Host supports UHS DDR50 mode */
+#define MMC_CAP_SET_XPC_330	(1 << 20)	/* Host supports >150mA current at 3.3V */
+#define MMC_CAP_SET_XPC_300	(1 << 21)	/* Host supports >150mA current at 3.0V */
+#define MMC_CAP_SET_XPC_180	(1 << 22)	/* Host supports >150mA current at 1.8V */
 
 	mmc_pm_flag_t		pm_caps;	/* supported pm features */
 
diff --git a/include/linux/mmc/sd.h b/include/linux/mmc/sd.h
index 3fd85e0..c648878 100644
--- a/include/linux/mmc/sd.h
+++ b/include/linux/mmc/sd.h
@@ -17,6 +17,7 @@
 /* This is basically the same command as for MMC with some quirks. */
 #define SD_SEND_RELATIVE_ADDR     3   /* bcr                     R6  */
 #define SD_SEND_IF_COND           8   /* bcr  [11:0] See below   R7  */
+#define SD_SWITCH_VOLTAGE         11  /* ac                      R1  */
 
   /* class 10 */
 #define SD_SWITCH                 6   /* adtc [31:0] See below   R1  */
@@ -32,6 +33,12 @@
 #define SD_APP_OP_COND           41   /* bcr  [31:0] OCR         R3  */
 #define SD_APP_SEND_SCR          51   /* adtc                    R1  */
 
+/* OCR bit definitions */
+#define SD_OCR_S18R		(1 << 24)    /* 1.8V switching request */
+#define SD_ROCR_S18A		SD_OCR_S18R  /* 1.8V switching accepted by card */
+#define SD_OCR_XPC		(1 << 28)    /* SDXC power control */
+#define SD_OCR_CCS		(1 << 30)    /* Card Capacity Status */
+
 /*
  * SD_SWITCH argument format:
  *
