mmc: dw_mmc: Support voltage changes

For UHS cards we need the ability to switch voltages from 3.3V to
1.8V.  Add support to the dw_mmc driver to handle this.  Note that
dw_mmc needs a little bit of extra code since the interface needs a
special bit programmed to the CMD register while CMD11 is progressing.
This means adding a few extra states to the state machine to track.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/dw_mmc.c

@@ -29,6 +29,7 @@
 #include <linux/irq.h>
 #include <linux/mmc/host.h>
 #include <linux/mmc/mmc.h>
+#include <linux/mmc/sd.h>
 #include <linux/mmc/sdio.h>
 #include <linux/mmc/dw_mmc.h>
 #include <linux/bitops.h>
@@ -234,10 +235,13 @@ err:
 }
 #endif /* defined(CONFIG_DEBUG_FS) */
 
+static void mci_send_cmd(struct dw_mci_slot *slot, u32 cmd, u32 arg);
+
 static u32 dw_mci_prepare_command(struct mmc_host *mmc, struct mmc_command *cmd)
 {
 	struct mmc_data	*data;
 	struct dw_mci_slot *slot = mmc_priv(mmc);
+	struct dw_mci *host = slot->host;
 	const struct dw_mci_drv_data *drv_data = slot->host->drv_data;
 	u32 cmdr;
 	cmd->error = -EINPROGRESS;
@@ -253,6 +257,34 @@ static u32 dw_mci_prepare_command(struct mmc_host *mmc, struct mmc_command *cmd)
 	else if (cmd->opcode != MMC_SEND_STATUS && cmd->data)
 		cmdr |= SDMMC_CMD_PRV_DAT_WAIT;
 
+	if (cmd->opcode == SD_SWITCH_VOLTAGE) {
+		u32 clk_en_a;
+
+		/* Special bit makes CMD11 not die */
+		cmdr |= SDMMC_CMD_VOLT_SWITCH;
+
+		/* Change state to continue to handle CMD11 weirdness */
+		WARN_ON(slot->host->state != STATE_SENDING_CMD);
+		slot->host->state = STATE_SENDING_CMD11;
+
+		/*
+		 * We need to disable low power mode (automatic clock stop)
+		 * while doing voltage switch so we don't confuse the card,
+		 * since stopping the clock is a specific part of the UHS
+		 * voltage change dance.
+		 *
+		 * Note that low power mode (SDMMC_CLKEN_LOW_PWR) will be
+		 * unconditionally turned back on in dw_mci_setup_bus() if it's
+		 * ever called with a non-zero clock.  That shouldn't happen
+		 * until the voltage change is all done.
+		 */
+		clk_en_a = mci_readl(host, CLKENA);
+		clk_en_a &= ~(SDMMC_CLKEN_LOW_PWR << slot->id);
+		mci_writel(host, CLKENA, clk_en_a);
+		mci_send_cmd(slot, SDMMC_CMD_UPD_CLK |
+			     SDMMC_CMD_PRV_DAT_WAIT, 0);
+	}
+
 	if (cmd->flags & MMC_RSP_PRESENT) {
 		/* We expect a response, so set this bit */
 		cmdr |= SDMMC_CMD_RESP_EXP;
@@ -775,11 +807,15 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
 	unsigned int clock = slot->clock;
 	u32 div;
 	u32 clk_en_a;
+	u32 sdmmc_cmd_bits = SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT;
+
+	/* We must continue to set bit 28 in CMD until the change is complete */
+	if (host->state == STATE_WAITING_CMD11_DONE)
+		sdmmc_cmd_bits |= SDMMC_CMD_VOLT_SWITCH;
 
 	if (!clock) {
 		mci_writel(host, CLKENA, 0);
-		mci_send_cmd(slot,
-			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
+		mci_send_cmd(slot, sdmmc_cmd_bits, 0);
 	} else if (clock != host->current_speed || force_clkinit) {
 		div = host->bus_hz / clock;
 		if (host->bus_hz % clock && host->bus_hz > clock)
@@ -803,15 +839,13 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
 		mci_writel(host, CLKSRC, 0);
 
 		/* inform CIU */
-		mci_send_cmd(slot,
-			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
+		mci_send_cmd(slot, sdmmc_cmd_bits, 0);
 
 		/* set clock to desired speed */
 		mci_writel(host, CLKDIV, div);
 
 		/* inform CIU */
-		mci_send_cmd(slot,
-			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
+		mci_send_cmd(slot, sdmmc_cmd_bits, 0);
 
 		/* enable clock; only low power if no SDIO */
 		clk_en_a = SDMMC_CLKEN_ENABLE << slot->id;
@@ -820,8 +854,7 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
 		mci_writel(host, CLKENA, clk_en_a);
 
 		/* inform CIU */
-		mci_send_cmd(slot,
-			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
+		mci_send_cmd(slot, sdmmc_cmd_bits, 0);
 
 		/* keep the clock with reflecting clock dividor */
 		slot->__clk_old = clock << div;
@@ -897,6 +930,17 @@ static void dw_mci_queue_request(struct dw_mci *host, struct dw_mci_slot *slot,
 
 	slot->mrq = mrq;
 
+	if (host->state == STATE_WAITING_CMD11_DONE) {
+		dev_warn(&slot->mmc->class_dev,
+			 "Voltage change didn't complete\n");
+		/*
+		 * this case isn't expected to happen, so we can
+		 * either crash here or just try to continue on
+		 * in the closest possible state
+		 */
+		host->state = STATE_IDLE;
+	}
+
 	if (host->state == STATE_IDLE) {
 		host->state = STATE_SENDING_CMD;
 		dw_mci_start_request(host, slot);
@@ -973,6 +1017,9 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 	/* Slot specific timing and width adjustment */
 	dw_mci_setup_bus(slot, false);
 
+	if (slot->host->state == STATE_WAITING_CMD11_DONE && ios->clock != 0)
+		slot->host->state = STATE_IDLE;
+
 	switch (ios->power_mode) {
 	case MMC_POWER_UP:
 		if (!IS_ERR(mmc->supply.vmmc)) {
@@ -1016,6 +1063,59 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 	}
 }
 
+static int dw_mci_card_busy(struct mmc_host *mmc)
+{
+	struct dw_mci_slot *slot = mmc_priv(mmc);
+	u32 status;
+
+	/*
+	 * Check the busy bit which is low when DAT[3:0]
+	 * (the data lines) are 0000
+	 */
+	status = mci_readl(slot->host, STATUS);
+
+	return !!(status & SDMMC_STATUS_BUSY);
+}
+
+static int dw_mci_switch_voltage(struct mmc_host *mmc, struct mmc_ios *ios)
+{
+	struct dw_mci_slot *slot = mmc_priv(mmc);
+	struct dw_mci *host = slot->host;
+	u32 uhs;
+	u32 v18 = SDMMC_UHS_18V << slot->id;
+	int min_uv, max_uv;
+	int ret;
+
+	/*
+	 * Program the voltage.  Note that some instances of dw_mmc may use
+	 * the UHS_REG for this.  For other instances (like exynos) the UHS_REG
+	 * does no harm but you need to set the regulator directly.  Try both.
+	 */
+	uhs = mci_readl(host, UHS_REG);
+	if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_330) {
+		min_uv = 2700000;
+		max_uv = 3600000;
+		uhs &= ~v18;
+	} else {
+		min_uv = 1700000;
+		max_uv = 1950000;
+		uhs |= v18;
+	}
+	if (!IS_ERR(mmc->supply.vqmmc)) {
+		ret = regulator_set_voltage(mmc->supply.vqmmc, min_uv, max_uv);
+
+		if (ret) {
+			dev_err(&mmc->class_dev,
+					 "Regulator set error %d: %d - %d\n",
+					 ret, min_uv, max_uv);
+			return ret;
+		}
+	}
+	mci_writel(host, UHS_REG, uhs);
+
+	return 0;
+}
+
 static int dw_mci_get_ro(struct mmc_host *mmc)
 {
 	int read_only;
@@ -1158,6 +1258,9 @@ static const struct mmc_host_ops dw_mci_ops = {
 	.get_cd			= dw_mci_get_cd,
 	.enable_sdio_irq	= dw_mci_enable_sdio_irq,
 	.execute_tuning		= dw_mci_execute_tuning,
+	.card_busy		= dw_mci_card_busy,
+	.start_signal_voltage_switch = dw_mci_switch_voltage,
+
 };
 
 static void dw_mci_request_end(struct dw_mci *host, struct mmc_request *mrq)
@@ -1181,7 +1284,11 @@ static void dw_mci_request_end(struct dw_mci *host, struct mmc_request *mrq)
 		dw_mci_start_request(host, slot);
 	} else {
 		dev_vdbg(host->dev, "list empty\n");
-		host->state = STATE_IDLE;
+
+		if (host->state == STATE_SENDING_CMD11)
+			host->state = STATE_WAITING_CMD11_DONE;
+		else
+			host->state = STATE_IDLE;
 	}
 
 	spin_unlock(&host->lock);
@@ -1292,8 +1399,10 @@ static void dw_mci_tasklet_func(unsigned long priv)
 
 		switch (state) {
 		case STATE_IDLE:
+		case STATE_WAITING_CMD11_DONE:
 			break;
 
+		case STATE_SENDING_CMD11:
 		case STATE_SENDING_CMD:
 			if (!test_and_clear_bit(EVENT_CMD_COMPLETE,
 						&host->pending_events))
@@ -1894,6 +2003,14 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
 	}
 
 	if (pending) {
+		/* Check volt switch first, since it can look like an error */
+		if ((host->state == STATE_SENDING_CMD11) &&
+		    (pending & SDMMC_INT_VOLT_SWITCH)) {
+			mci_writel(host, RINTSTS, SDMMC_INT_VOLT_SWITCH);
+			pending &= ~SDMMC_INT_VOLT_SWITCH;
+			dw_mci_cmd_interrupt(host, pending);
+		}
+
 		if (pending & DW_MCI_CMD_ERROR_FLAGS) {
 			mci_writel(host, RINTSTS, DW_MCI_CMD_ERROR_FLAGS);
 			host->cmd_status = pending;
@@ -1999,7 +2116,9 @@ static void dw_mci_work_routine_card(struct work_struct *work)
 
 					switch (host->state) {
 					case STATE_IDLE:
+					case STATE_WAITING_CMD11_DONE:
 						break;
+					case STATE_SENDING_CMD11:
 					case STATE_SENDING_CMD:
 						mrq->cmd->error = -ENOMEDIUM;
 						if (!mrq->data)

drivers/mmc/host/dw_mmc.h

@@ -99,6 +99,7 @@
 #define SDMMC_INT_HLE			BIT(12)
 #define SDMMC_INT_FRUN			BIT(11)
 #define SDMMC_INT_HTO			BIT(10)
+#define SDMMC_INT_VOLT_SWITCH		BIT(10) /* overloads bit 10! */
 #define SDMMC_INT_DRTO			BIT(9)
 #define SDMMC_INT_RTO			BIT(8)
 #define SDMMC_INT_DCRC			BIT(7)
@@ -113,6 +114,7 @@
 /* Command register defines */
 #define SDMMC_CMD_START			BIT(31)
 #define SDMMC_CMD_USE_HOLD_REG	BIT(29)
+#define SDMMC_CMD_VOLT_SWITCH		BIT(28)
 #define SDMMC_CMD_CCS_EXP		BIT(23)
 #define SDMMC_CMD_CEATA_RD		BIT(22)
 #define SDMMC_CMD_UPD_CLK		BIT(21)
@@ -130,6 +132,7 @@
 /* Status register defines */
 #define SDMMC_GET_FCNT(x)		(((x)>>17) & 0x1FFF)
 #define SDMMC_STATUS_DMA_REQ		BIT(31)
+#define SDMMC_STATUS_BUSY		BIT(9)
 /* FIFOTH register defines */
 #define SDMMC_SET_FIFOTH(m, r, t)	(((m) & 0x7) << 28 | \
 					 ((r) & 0xFFF) << 16 | \
@@ -150,7 +153,7 @@
 #define SDMMC_GET_VERID(x)		((x) & 0xFFFF)
 /* Card read threshold */
 #define SDMMC_SET_RD_THLD(v, x)		(((v) & 0x1FFF) << 16 | (x))
-
+#define SDMMC_UHS_18V			BIT(0)
 /* All ctrl reset bits */
 #define SDMMC_CTRL_ALL_RESET_FLAGS \
 	(SDMMC_CTRL_RESET | SDMMC_CTRL_FIFO_RESET | SDMMC_CTRL_DMA_RESET)

include/linux/mmc/dw_mmc.h

@@ -26,6 +26,8 @@ enum dw_mci_state {
 	STATE_DATA_BUSY,
 	STATE_SENDING_STOP,
 	STATE_DATA_ERROR,
+	STATE_SENDING_CMD11,
+	STATE_WAITING_CMD11_DONE,
 };
 
 enum {