xref: /freebsd-10-stable/sys/arm/freescale/imx/imx_sdhci.c

/*-
 * Copyright (c) 2013 Ian Lepore <ian@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: stable/10/sys/arm/freescale/imx/imx_sdhci.c 266152 2014-05-15 16:11:06Z ian $");

/*
 * SDHCI driver glue for Freescale i.MX SoC family.
 *
 * This supports both eSDHC (earlier SoCs) and uSDHC (more recent SoCs).
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/resource.h>
#include <sys/rman.h>
#include <sys/taskqueue.h>

#include <machine/bus.h>
#include <machine/resource.h>
#include <machine/intr.h>

#include <arm/freescale/imx/imx51_ccmvar.h>

#include <dev/ofw/ofw_bus.h>
#include <dev/ofw/ofw_bus_subr.h>

#include <dev/mmc/bridge.h>
#include <dev/mmc/mmcreg.h>
#include <dev/mmc/mmcbrvar.h>

#include <dev/sdhci/sdhci.h>
#include "sdhci_if.h"

struct imx_sdhci_softc {
	device_t		dev;
	struct resource *	mem_res;
	struct resource *	irq_res;
	void *			intr_cookie;
	struct sdhci_slot	slot;
	uint32_t		baseclk_hz;
	uint32_t		sdclockreg_freq_bits;
	uint32_t		cmd_and_mode;
	uint32_t		r1bfix_intmask;
	uint8_t			r1bfix_type;
	uint8_t			hwtype;
};

#define	R1BFIX_NONE	0	/* No fix needed at next interrupt. */
#define	R1BFIX_NODATA	1	/* Synthesize DATA_END for R1B w/o data. */
#define	R1BFIX_AC12	2	/* Wait for busy after auto command 12. */

#define	HWTYPE_NONE	0	/* Hardware not recognized/supported. */
#define	HWTYPE_ESDHC	1	/* imx5x and earlier. */
#define	HWTYPE_USDHC	2	/* imx6. */

#define	SDHC_WTMK_LVL		0x44	/* Watermark Level register. */
#define	USDHC_MIX_CONTROL	0x48	/* Mix(ed) Control register. */
#define	SDHC_VEND_SPEC		0xC0	/* Vendor-specific register. */
#define	 SDHC_VEND_FRC_SDCLK_ON	(1 <<  8)
#define	 SDHC_VEND_IPGEN	(1 << 11)
#define	 SDHC_VEND_HCKEN	(1 << 12)
#define	 SDHC_VEND_PEREN	(1 << 13)

#define	SDHC_PROT_CTRL		0x28
#define	 SDHC_PROT_LED		(1 << 0)
#define	 SDHC_PROT_WIDTH_1BIT	(0 << 1)
#define	 SDHC_PROT_WIDTH_4BIT	(1 << 1)
#define	 SDHC_PROT_WIDTH_8BIT	(2 << 1)
#define	 SDHC_PROT_WIDTH_MASK	(3 << 1)
#define	 SDHC_PROT_D3CD		(1 << 3)
#define	 SDHC_PROT_EMODE_BIG	(0 << 4)
#define	 SDHC_PROT_EMODE_HALF	(1 << 4)
#define	 SDHC_PROT_EMODE_LITTLE	(2 << 4)
#define	 SDHC_PROT_EMODE_MASK	(3 << 4)
#define	 SDHC_PROT_SDMA		(0 << 8)
#define	 SDHC_PROT_ADMA1	(1 << 8)
#define	 SDHC_PROT_ADMA2	(2 << 8)
#define	 SDHC_PROT_ADMA264	(3 << 8)
#define	 SDHC_PROT_DMA_MASK	(3 << 8)
#define	 SDHC_PROT_CDTL		(1 << 6)
#define	 SDHC_PROT_CDSS		(1 << 7)

#define	SDHC_CLK_IPGEN		(1 << 0)
#define	SDHC_CLK_HCKEN		(1 << 1)
#define	SDHC_CLK_PEREN		(1 << 2)
#define	SDHC_CLK_DIVISOR_MASK	0x000000f0
#define	SDHC_CLK_DIVISOR_SHIFT	4
#define	SDHC_CLK_PRESCALE_MASK	0x0000ff00
#define	SDHC_CLK_PRESCALE_SHIFT	8

static struct ofw_compat_data compat_data[] = {
	{"fsl,imx6q-usdhc",	HWTYPE_USDHC},
	{"fsl,imx6sl-usdhc",	HWTYPE_USDHC},
	{"fsl,imx53-esdhc",	HWTYPE_ESDHC},
	{"fsl,imx51-esdhc",	HWTYPE_ESDHC},
	{NULL,			HWTYPE_NONE},
};;

static void imx_sdhc_set_clock(struct imx_sdhci_softc *sc, int enable);

static inline uint32_t
RD4(struct imx_sdhci_softc *sc, bus_size_t off)
{

	return (bus_read_4(sc->mem_res, off));
}

static inline void
WR4(struct imx_sdhci_softc *sc, bus_size_t off, uint32_t val)
{

	bus_write_4(sc->mem_res, off, val);
}

static uint8_t
imx_sdhci_read_1(device_t dev, struct sdhci_slot *slot, bus_size_t off)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);
	uint32_t val32, wrk32;

	/*
	 * Most of the things in the standard host control register are in the
	 * hardware's wider protocol control register, but some of the bits are
	 * moved around.
	 */
	if (off == SDHCI_HOST_CONTROL) {
		wrk32 = RD4(sc, SDHC_PROT_CTRL);
                val32 = wrk32 & (SDHCI_CTRL_LED | SDHCI_CTRL_CARD_DET |
		    SDHCI_CTRL_FORCE_CARD);
		switch (wrk32 & SDHC_PROT_WIDTH_MASK) {
		case SDHC_PROT_WIDTH_1BIT:
			/* Value is already 0. */
			break;
		case SDHC_PROT_WIDTH_4BIT:
			val32 |= SDHCI_CTRL_4BITBUS;
			break;
		case SDHC_PROT_WIDTH_8BIT:
			val32 |= SDHCI_CTRL_8BITBUS;
			break;
		}
		switch (wrk32 & SDHC_PROT_DMA_MASK) {
		case SDHC_PROT_SDMA:
			/* Value is already 0. */
			break;
		case SDHC_PROT_ADMA1:
                        /* This value is deprecated, should never appear. */
			break;
		case SDHC_PROT_ADMA2:
			val32 |= SDHCI_CTRL_ADMA2;
			break;
		case SDHC_PROT_ADMA264:
			val32 |= SDHCI_CTRL_ADMA264;
			break;
		}
		return val32;
	}

	/*
	 * XXX can't find the bus power on/off knob.  For now we have to say the
	 * power is always on and always set to the same voltage.
	 */
	if (off == SDHCI_POWER_CONTROL) {
                return (SDHCI_POWER_ON | SDHCI_POWER_300);
	}


	return ((RD4(sc, off & ~3) >> (off & 3) * 8) & 0xff);
}

static uint16_t
imx_sdhci_read_2(device_t dev, struct sdhci_slot *slot, bus_size_t off)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);
	uint32_t val32, wrk32;

	if (sc->hwtype == HWTYPE_USDHC) {
		/*
		 * The USDHC hardware has nothing in the version register, but
		 * it's v3 compatible with all our translation code.
		 */
		if (off == SDHCI_HOST_VERSION) {
			return (SDHCI_SPEC_300 << SDHCI_SPEC_VER_SHIFT);
		}
		/*
		 * The USDHC hardware moved the transfer mode bits to the mixed
		 * control register, fetch them from there.
		 */
		if (off == SDHCI_TRANSFER_MODE)
			return (RD4(sc, USDHC_MIX_CONTROL) & 0x37);

	} else if (sc->hwtype == HWTYPE_ESDHC) {

		/*
		 * The ESDHC hardware has the typical 32-bit combined "command
		 * and mode" register that we have to cache so that command
		 * isn't written until after mode.  On a read, just retrieve the
		 * cached values last written.
		 */
		if (off == SDHCI_TRANSFER_MODE) {
			return (sc->cmd_and_mode >> 16);
		} else if (off == SDHCI_COMMAND_FLAGS) {
			return (sc->cmd_and_mode & 0x0000ffff);
		}
	}

	/*
	 * This hardware only manages one slot.  Synthesize a slot interrupt
	 * status register... if there are any enabled interrupts active they
	 * must be coming from our one and only slot.
	 */
	if (off == SDHCI_SLOT_INT_STATUS) {
		val32  = RD4(sc, SDHCI_INT_STATUS);
		val32 &= RD4(sc, SDHCI_SIGNAL_ENABLE);
		return (val32 ? 1 : 0);
	}

	/*
	 * The clock enable bit is in the vendor register and the clock-stable
	 * bit is in the present state register.  Transcribe them as if they
	 * were in the clock control register where they should be.
	 * XXX Is it important that we distinguish between "internal" and "card"
	 * clocks?  Probably not; transcribe the card clock status to both bits.
	 */
	if (off == SDHCI_CLOCK_CONTROL) {
		val32 = 0;
		wrk32 = RD4(sc, SDHC_VEND_SPEC);
		if (wrk32 & SDHC_VEND_FRC_SDCLK_ON)
			val32 |= SDHCI_CLOCK_INT_EN | SDHCI_CLOCK_CARD_EN;
		wrk32 = RD4(sc, SDHCI_PRESENT_STATE);
		if (wrk32 & 0x08)
			val32 |= SDHCI_CLOCK_INT_STABLE;
		val32 |= sc->sdclockreg_freq_bits;
		return (val32);
	}

	return ((RD4(sc, off & ~3) >> (off & 3) * 8) & 0xffff);
}

static uint32_t
imx_sdhci_read_4(device_t dev, struct sdhci_slot *slot, bus_size_t off)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);
	uint32_t val32;

	/*
	 * The hardware leaves the base clock frequency out of the capabilities
	 * register; fill it in.  The timeout clock is the same as the active
	 * output sdclock; we indicate that with a quirk setting so don't
	 * populate the timeout frequency bits.
	 *
	 * XXX Turn off (for now) features the hardware can do but this driver
	 * doesn't yet handle (1.8v, suspend/resume, etc).
	 */
	if (off == SDHCI_CAPABILITIES) {
		val32 = RD4(sc, off);
		val32 &= ~SDHCI_CAN_VDD_180;
		val32 &= ~SDHCI_CAN_DO_SUSPEND;
		val32 |= SDHCI_CAN_DO_8BITBUS;
		val32 |= (sc->baseclk_hz / 1000000) << SDHCI_CLOCK_BASE_SHIFT;
		return (val32);
	}

	val32 = RD4(sc, off);

	/*
	 * imx_sdhci_intr() can synthesize a DATA_END interrupt following a
	 * command with an R1B response, mix it into the hardware status.
	 */
	if (off == SDHCI_INT_STATUS) {
		val32 |= sc->r1bfix_intmask;
	}

	return val32;
}

static void
imx_sdhci_read_multi_4(device_t dev, struct sdhci_slot *slot, bus_size_t off,
    uint32_t *data, bus_size_t count)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);

	bus_read_multi_4(sc->mem_res, off, data, count);
}

static void
imx_sdhci_write_1(device_t dev, struct sdhci_slot *slot, bus_size_t off, uint8_t val)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);
	uint32_t val32;

	/*
	 * Most of the things in the standard host control register are in the
	 * hardware's wider protocol control register, but some of the bits are
	 * moved around.
	 */
	if (off == SDHCI_HOST_CONTROL) {
		val32 = RD4(sc, SDHC_PROT_CTRL);
		val32 &= ~(SDHC_PROT_LED | SDHC_PROT_DMA_MASK |
		    SDHC_PROT_WIDTH_MASK | SDHC_PROT_CDTL | SDHC_PROT_CDSS);
		val32 |= (val & SDHCI_CTRL_LED);
		if (val & SDHCI_CTRL_8BITBUS)
			val32 |= SDHC_PROT_WIDTH_8BIT;
		else
			val32 |= (val & SDHCI_CTRL_4BITBUS);
		val32 |= (val & (SDHCI_CTRL_SDMA | SDHCI_CTRL_ADMA2)) << 4;
		val32 |= (val & (SDHCI_CTRL_CARD_DET | SDHCI_CTRL_FORCE_CARD));
		WR4(sc, SDHC_PROT_CTRL, val32);
		return;
	}

	/* XXX I can't find the bus power on/off knob; do nothing. */
	if (off == SDHCI_POWER_CONTROL) {
		return;
	}

	val32 = RD4(sc, off & ~3);
	val32 &= ~(0xff << (off & 3) * 8);
	val32 |= (val << (off & 3) * 8);

	WR4(sc, off & ~3, val32);
}

static void
imx_sdhci_write_2(device_t dev, struct sdhci_slot *slot, bus_size_t off, uint16_t val)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);
	uint32_t val32;

	/* The USDHC hardware moved the transfer mode bits to mixed control. */
	if (sc->hwtype == HWTYPE_USDHC) {
		if (off == SDHCI_TRANSFER_MODE) {
			val32 = RD4(sc, USDHC_MIX_CONTROL);
			val32 &= ~0x3f;
			val32 |= val & 0x37;
			// XXX acmd23 not supported here (or by sdhci driver)
			WR4(sc, USDHC_MIX_CONTROL, val32);
			return;
		}
	}

	/*
	 * The clock control stuff is complex enough to have its own routine
	 * that can both change speeds and en/disable the clock output. Also,
	 * save the register bits in SDHCI format so that we can play them back
	 * in the read2 routine without complex decoding.
	 */
	if (off == SDHCI_CLOCK_CONTROL) {
		sc->sdclockreg_freq_bits = val & 0xffc0;
		if (val & SDHCI_CLOCK_CARD_EN) {
			imx_sdhc_set_clock(sc, true);
		} else {
			imx_sdhc_set_clock(sc, false);
		}
	}

	/*
	 * Figure out whether we need to check the DAT0 line for busy status at
	 * interrupt time.  The controller should be doing this, but for some
	 * reason it doesn't.  There are two cases:
	 *  - R1B response with no data transfer should generate a DATA_END (aka
	 *    TRANSFER_COMPLETE) interrupt after waiting for busy, but if
	 *    there's no data transfer there's no DATA_END interrupt.  This is
	 *    documented; they seem to think it's a feature.
	 *  - R1B response after Auto-CMD12 appears to not work, even though
	 *    there's a control bit for it (bit 3) in the vendor register.
	 * When we're starting a command that needs a manual DAT0 line check at
	 * interrupt time, we leave ourselves a note in r1bfix_type so that we
	 * can do the extra work in imx_sdhci_intr().
	 */
	if (off == SDHCI_COMMAND_FLAGS) {
		if (val & SDHCI_CMD_DATA) {
			const uint32_t MBAUTOCMD = SDHCI_TRNS_ACMD12 | SDHCI_TRNS_MULTI;
			val32 = RD4(sc, USDHC_MIX_CONTROL);
			if ((val32 & MBAUTOCMD) == MBAUTOCMD)
				sc->r1bfix_type = R1BFIX_AC12;
		} else {
			if ((val & SDHCI_CMD_RESP_MASK) == SDHCI_CMD_RESP_SHORT_BUSY) {
				WR4(sc, SDHCI_INT_ENABLE, slot->intmask | SDHCI_INT_RESPONSE);
				WR4(sc, SDHCI_SIGNAL_ENABLE, slot->intmask | SDHCI_INT_RESPONSE);
				sc->r1bfix_type = R1BFIX_NODATA;
			}
		}
	}

	val32 = RD4(sc, off & ~3);
	val32 &= ~(0xffff << (off & 3) * 8);
	val32 |= ((val & 0xffff) << (off & 3) * 8);
	WR4(sc, off & ~3, val32);
}

static void
imx_sdhci_write_4(device_t dev, struct sdhci_slot *slot, bus_size_t off, uint32_t val)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);

	/* Clear synthesized interrupts, then pass the value to the hardware. */
	if (off == SDHCI_INT_STATUS) {
		sc->r1bfix_intmask &= ~val;
	}

	WR4(sc, off, val);
}

static void
imx_sdhci_write_multi_4(device_t dev, struct sdhci_slot *slot, bus_size_t off,
    uint32_t *data, bus_size_t count)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);

	bus_write_multi_4(sc->mem_res, off, data, count);
}

static void
imx_sdhc_set_clock(struct imx_sdhci_softc *sc, int enable)
{
	uint32_t divisor, enable_bits, enable_reg, freq, prescale, val32;

	if (sc->hwtype == HWTYPE_ESDHC) {
		divisor = (sc->sdclockreg_freq_bits >> SDHCI_DIVIDER_SHIFT) &
		    SDHCI_DIVIDER_MASK;
		enable_reg = SDHCI_CLOCK_CONTROL;
		enable_bits = SDHC_CLK_IPGEN | SDHC_CLK_HCKEN |
		    SDHC_CLK_PEREN;
	} else {
		divisor = (sc->sdclockreg_freq_bits >> SDHCI_DIVIDER_SHIFT) &
		    SDHCI_DIVIDER_MASK;
		divisor |= ((sc->sdclockreg_freq_bits >>
		    SDHCI_DIVIDER_HI_SHIFT) &
		    SDHCI_DIVIDER_HI_MASK) << SDHCI_DIVIDER_MASK_LEN;
		enable_reg = SDHCI_CLOCK_CONTROL;
		enable_bits = SDHC_VEND_IPGEN | SDHC_VEND_HCKEN |
		   SDHC_VEND_PEREN;
	}

	WR4(sc, SDHC_VEND_SPEC,
	    RD4(sc, SDHC_VEND_SPEC) & ~SDHC_VEND_FRC_SDCLK_ON);
	WR4(sc, enable_reg, RD4(sc, enable_reg) & ~enable_bits);

	if (!enable)
		return;

	if (divisor == 0)
		freq = sc->baseclk_hz;
	else
		freq = sc->baseclk_hz / (2 * divisor);

	for (prescale = 2; prescale < freq / prescale / 16;)
		prescale <<= 1;

	for (divisor = 1; freq < freq / prescale / divisor;)
		++divisor;

	prescale >>= 1;
	divisor -= 1;

	val32 = RD4(sc, SDHCI_CLOCK_CONTROL);
	val32 &= ~SDHC_CLK_DIVISOR_MASK;
	val32 |= divisor << SDHC_CLK_DIVISOR_SHIFT;
	val32 &= ~SDHC_CLK_PRESCALE_MASK;
	val32 |= prescale << SDHC_CLK_PRESCALE_SHIFT;
	WR4(sc, SDHCI_CLOCK_CONTROL, val32);

	WR4(sc, enable_reg, RD4(sc, enable_reg) | enable_bits);
	WR4(sc, SDHC_VEND_SPEC,
	    RD4(sc, SDHC_VEND_SPEC) | SDHC_VEND_FRC_SDCLK_ON);
}

static void
imx_sdhci_intr(void *arg)
{
	struct imx_sdhci_softc *sc = arg;
	uint32_t intmask;

	intmask = RD4(sc, SDHCI_INT_STATUS);

	/*
	 * Manually check the DAT0 line for R1B response types that the
	 * controller fails to handle properly.
	 *
	 * To do the NODATA fix, when the RESPONSE (COMMAND_COMPLETE) interrupt
	 * occurs, we have to wait for the DAT0 line to be released, then
	 * synthesize a DATA_END (TRANSFER_COMPLETE) interrupt, which we do by
	 * storing SDHCI_INT_DATA_END into a variable that gets ORed into the
	 * return value when the SDHCI_INT_STATUS register is read.
	 *
	 * For the AC12 fix, when the DATA_END interrupt occurs we wait for the
	 * DAT0 line to be released, and the waiting is all the fix we need.
	 */
	if ((sc->r1bfix_type == R1BFIX_NODATA &&
	    (intmask & SDHCI_INT_RESPONSE)) ||
	    (sc->r1bfix_type == R1BFIX_AC12 &&
	    (intmask & SDHCI_INT_DATA_END))) {
		uint32_t count;
		count = 0;
		/* XXX use a callout or something instead of busy-waiting. */
		while (count < 250000 &&
		       (RD4(sc, SDHCI_PRESENT_STATE) & SDHCI_DAT_ACTIVE)) {
			++count;
			DELAY(1);
		}
		if (count >= 250000)
			sc->r1bfix_intmask = SDHCI_INT_DATA_TIMEOUT;
		else if (sc->r1bfix_type == R1BFIX_NODATA)
			sc->r1bfix_intmask = SDHCI_INT_DATA_END;
		sc->r1bfix_type = R1BFIX_NONE;
	}

	sdhci_generic_intr(&sc->slot);
}

static int
imx_sdhci_get_ro(device_t bus, device_t child)
{

	return (false);
}

static int
imx_sdhci_detach(device_t dev)
{

	return (EBUSY);
}

static int
imx_sdhci_attach(device_t dev)
{
	struct imx_sdhci_softc *sc = device_get_softc(dev);
	int rid, err;

	sc->dev = dev;

	sc->hwtype = ofw_bus_search_compatible(dev, compat_data)->ocd_data;
	if (sc->hwtype == HWTYPE_NONE)
		panic("Impossible: not compatible in imx_sdhci_attach()");

	rid = 0;
	sc->mem_res = bus_alloc_resource_any(dev, SYS_RES_MEMORY, &rid,
	    RF_ACTIVE);
	if (!sc->mem_res) {
		device_printf(dev, "cannot allocate memory window\n");
		err = ENXIO;
		goto fail;
	}

	rid = 0;
	sc->irq_res = bus_alloc_resource_any(dev, SYS_RES_IRQ, &rid,
	    RF_ACTIVE);
	if (!sc->irq_res) {
		device_printf(dev, "cannot allocate interrupt\n");
		err = ENXIO;
		goto fail;
	}

	if (bus_setup_intr(dev, sc->irq_res, INTR_TYPE_BIO | INTR_MPSAFE,
	    NULL, imx_sdhci_intr, sc, &sc->intr_cookie)) {
		device_printf(dev, "cannot setup interrupt handler\n");
		err = ENXIO;
		goto fail;
	}

	sc->slot.quirks |= SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK;

	/*
	 * DMA is not really broken, I just haven't implemented it yet.
	 */
	sc->slot.quirks |= SDHCI_QUIRK_BROKEN_DMA;

	/*
	 * Set the buffer watermark level to 128 words (512 bytes) for both read
	 * and write.  The hardware has a restriction that when the read or
	 * write ready status is asserted, that means you can read exactly the
	 * number of words set in the watermark register before you have to
	 * re-check the status and potentially wait for more data.  The main
	 * sdhci driver provides no hook for doing status checking on less than
	 * a full block boundary, so we set the watermark level to be a full
	 * block.  Reads and writes where the block size is less than the
	 * watermark size will work correctly too, no need to change the
	 * watermark for different size blocks.  However, 128 is the maximum
	 * allowed for the watermark, so PIO is limitted to 512 byte blocks
	 * (which works fine for SD cards, may be a problem for SDIO some day).
	 *
	 * XXX need named constants for this stuff.
	 */
	WR4(sc, SDHC_WTMK_LVL, 0x08800880);

	/* XXX get imx6 clock frequency from CCM */
	if (sc->hwtype == HWTYPE_USDHC) {
		sc->baseclk_hz = 200000000;
	} else if (sc->hwtype == HWTYPE_ESDHC) {
		sc->baseclk_hz = imx51_get_clock(IMX51CLK_PERCLK_ROOT);
	}

	sdhci_init_slot(dev, &sc->slot, 0);

	bus_generic_probe(dev);
	bus_generic_attach(dev);

	sdhci_start_slot(&sc->slot);

	return (0);

fail:
	if (sc->intr_cookie)
		bus_teardown_intr(dev, sc->irq_res, sc->intr_cookie);
	if (sc->irq_res)
		bus_release_resource(dev, SYS_RES_IRQ, 0, sc->irq_res);
	if (sc->mem_res)
		bus_release_resource(dev, SYS_RES_MEMORY, 0, sc->mem_res);

	return (err);
}

static int
imx_sdhci_probe(device_t dev)
{

        if (!ofw_bus_status_okay(dev))
		return (ENXIO);

	switch (ofw_bus_search_compatible(dev, compat_data)->ocd_data) {
	case HWTYPE_ESDHC:
		device_set_desc(dev, "Freescale eSDHC controller");
		return (BUS_PROBE_DEFAULT);
	case HWTYPE_USDHC:
		device_set_desc(dev, "Freescale uSDHC controller");
		return (BUS_PROBE_DEFAULT);
	default:
		break;
	}
	return (ENXIO);
}

static device_method_t imx_sdhci_methods[] = {
	/* Device interface */
	DEVMETHOD(device_probe,		imx_sdhci_probe),
	DEVMETHOD(device_attach,	imx_sdhci_attach),
	DEVMETHOD(device_detach,	imx_sdhci_detach),

	/* Bus interface */
	DEVMETHOD(bus_read_ivar,	sdhci_generic_read_ivar),
	DEVMETHOD(bus_write_ivar,	sdhci_generic_write_ivar),
	DEVMETHOD(bus_print_child,	bus_generic_print_child),

	/* MMC bridge interface */
	DEVMETHOD(mmcbr_update_ios,	sdhci_generic_update_ios),
	DEVMETHOD(mmcbr_request,	sdhci_generic_request),
	DEVMETHOD(mmcbr_get_ro,		imx_sdhci_get_ro),
	DEVMETHOD(mmcbr_acquire_host,	sdhci_generic_acquire_host),
	DEVMETHOD(mmcbr_release_host,	sdhci_generic_release_host),

	/* SDHCI registers accessors */
	DEVMETHOD(sdhci_read_1,		imx_sdhci_read_1),
	DEVMETHOD(sdhci_read_2,		imx_sdhci_read_2),
	DEVMETHOD(sdhci_read_4,		imx_sdhci_read_4),
	DEVMETHOD(sdhci_read_multi_4,	imx_sdhci_read_multi_4),
	DEVMETHOD(sdhci_write_1,	imx_sdhci_write_1),
	DEVMETHOD(sdhci_write_2,	imx_sdhci_write_2),
	DEVMETHOD(sdhci_write_4,	imx_sdhci_write_4),
	DEVMETHOD(sdhci_write_multi_4,	imx_sdhci_write_multi_4),

	{ 0, 0 }
};

static devclass_t imx_sdhci_devclass;

static driver_t imx_sdhci_driver = {
	"sdhci_imx",
	imx_sdhci_methods,
	sizeof(struct imx_sdhci_softc),
};

DRIVER_MODULE(sdhci_imx, simplebus, imx_sdhci_driver, imx_sdhci_devclass, 0, 0);
MODULE_DEPEND(sdhci_imx, sdhci, 1, 1, 1);