linux/drivers/mmc/core/core.c

/*
 *  linux/drivers/mmc/core/core.c
 *
 *  Copyright (C) 2003-2004 Russell King, All Rights Reserved.
 *  SD support Copyright (C) 2004 Ian Molton, All Rights Reserved.
 *  Copyright (C) 2005-2008 Pierre Ossman, All Rights Reserved.
 *  MMCv4 support Copyright (C) 2006 Philip Langdale, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/pagemap.h>
#include <linux/err.h>
#include <linux/leds.h>
#include <linux/scatterlist.h>
#include <linux/log2.h>
#include <linux/regulator/consumer.h>

#include <linux/mmc/card.h>
#include <linux/mmc/host.h>
#include <linux/mmc/mmc.h>
#include <linux/mmc/sd.h>

#include "core.h"
#include "bus.h"
#include "host.h"
#include "sdio_bus.h"

#include "mmc_ops.h"
#include "sd_ops.h"
#include "sdio_ops.h"

static struct workqueue_struct *workqueue;

/*
 * Enabling software CRCs on the data blocks can be a significant (30%)
 * performance cost, and for other reasons may not always be desired.
 * So we allow it it to be disabled.
 */
int use_spi_crc = 1;
module_param(use_spi_crc, bool, 0);

/*
 * Internal function. Schedule delayed work in the MMC work queue.
 */
static int mmc_schedule_delayed_work(struct delayed_work *work,
				     unsigned long delay)
{
	return queue_delayed_work(workqueue, work, delay);
}

/*
 * Internal function. Flush all scheduled work from the MMC work queue.
 */
static void mmc_flush_scheduled_work(void)
{
	flush_workqueue(workqueue);
}

/**
 *	mmc_request_done - finish processing an MMC request
 *	@host: MMC host which completed request
 *	@mrq: MMC request which request
 *
 *	MMC drivers should call this function when they have completed
 *	their processing of a request.
 */
void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
{
	struct mmc_command *cmd = mrq->cmd;
	int err = cmd->error;

	if (err && cmd->retries && mmc_host_is_spi(host)) {
		if (cmd->resp[0] & R1_SPI_ILLEGAL_COMMAND)
			cmd->retries = 0;
	}

	if (err && cmd->retries) {
		pr_debug("%s: req failed (CMD%u): %d, retrying...\n",
			mmc_hostname(host), cmd->opcode, err);

		cmd->retries--;
		cmd->error = 0;
		host->ops->request(host, mrq);
	} else {
		led_trigger_event(host->led, LED_OFF);

		pr_debug("%s: req done (CMD%u): %d: %08x %08x %08x %08x\n",
			mmc_hostname(host), cmd->opcode, err,
			cmd->resp[0], cmd->resp[1],
			cmd->resp[2], cmd->resp[3]);

		if (mrq->data) {
			pr_debug("%s:     %d bytes transferred: %d\n",
				mmc_hostname(host),
				mrq->data->bytes_xfered, mrq->data->error);
		}

		if (mrq->stop) {
			pr_debug("%s:     (CMD%u): %d: %08x %08x %08x %08x\n",
				mmc_hostname(host), mrq->stop->opcode,
				mrq->stop->error,
				mrq->stop->resp[0], mrq->stop->resp[1],
				mrq->stop->resp[2], mrq->stop->resp[3]);
		}

		if (mrq->done)
			mrq->done(mrq);
	}
}

EXPORT_SYMBOL(mmc_request_done);

static void
mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
{
#ifdef CONFIG_MMC_DEBUG
	unsigned int i, sz;
	struct scatterlist *sg;
#endif

	pr_debug("%s: starting CMD%u arg %08x flags %08x\n",
		 mmc_hostname(host), mrq->cmd->opcode,
		 mrq->cmd->arg, mrq->cmd->flags);

	if (mrq->data) {
		pr_debug("%s:     blksz %d blocks %d flags %08x "
			"tsac %d ms nsac %d\n",
			mmc_hostname(host), mrq->data->blksz,
			mrq->data->blocks, mrq->data->flags,
			mrq->data->timeout_ns / 1000000,
			mrq->data->timeout_clks);
	}

	if (mrq->stop) {
		pr_debug("%s:     CMD%u arg %08x flags %08x\n",
			 mmc_hostname(host), mrq->stop->opcode,
			 mrq->stop->arg, mrq->stop->flags);
	}

	WARN_ON(!host->claimed);

	led_trigger_event(host->led, LED_FULL);

	mrq->cmd->error = 0;
	mrq->cmd->mrq = mrq;
	if (mrq->data) {
		BUG_ON(mrq->data->blksz > host->max_blk_size);
		BUG_ON(mrq->data->blocks > host->max_blk_count);
		BUG_ON(mrq->data->blocks * mrq->data->blksz >
			host->max_req_size);

#ifdef CONFIG_MMC_DEBUG
		sz = 0;
		for_each_sg(mrq->data->sg, sg, mrq->data->sg_len, i)
			sz += sg->length;
		BUG_ON(sz != mrq->data->blocks * mrq->data->blksz);
#endif

		mrq->cmd->data = mrq->data;
		mrq->data->error = 0;
		mrq->data->mrq = mrq;
		if (mrq->stop) {
			mrq->data->stop = mrq->stop;
			mrq->stop->error = 0;
			mrq->stop->mrq = mrq;
		}
	}
	host->ops->request(host, mrq);
}

static void mmc_wait_done(struct mmc_request *mrq)
{
	complete(mrq->done_data);
}

/**
 *	mmc_wait_for_req - start a request and wait for completion
 *	@host: MMC host to start command
 *	@mrq: MMC request to start
 *
 *	Start a new MMC custom command request for a host, and wait
 *	for the command to complete. Does not attempt to parse the
 *	response.
 */
void mmc_wait_for_req(struct mmc_host *host, struct mmc_request *mrq)
{
	DECLARE_COMPLETION_ONSTACK(complete);

	mrq->done_data = &complete;
	mrq->done = mmc_wait_done;

	mmc_start_request(host, mrq);

	wait_for_completion(&complete);
}

EXPORT_SYMBOL(mmc_wait_for_req);

/**
 *	mmc_wait_for_cmd - start a command and wait for completion
 *	@host: MMC host to start command
 *	@cmd: MMC command to start
 *	@retries: maximum number of retries
 *
 *	Start a new MMC command for a host, and wait for the command
 *	to complete.  Return any error that occurred while the command
 *	was executing.  Do not attempt to parse the response.
 */
int mmc_wait_for_cmd(struct mmc_host *host, struct mmc_command *cmd, int retries)
{
	struct mmc_request mrq;

	WARN_ON(!host->claimed);

	memset(&mrq, 0, sizeof(struct mmc_request));

	memset(cmd->resp, 0, sizeof(cmd->resp));
	cmd->retries = retries;

	mrq.cmd = cmd;
	cmd->data = NULL;

	mmc_wait_for_req(host, &mrq);

	return cmd->error;
}

EXPORT_SYMBOL(mmc_wait_for_cmd);

/**
 *	mmc_set_data_timeout - set the timeout for a data command
 *	@data: data phase for command
 *	@card: the MMC card associated with the data transfer
 *
 *	Computes the data timeout parameters according to the
 *	correct algorithm given the card type.
 */
void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card)
{
	unsigned int mult;

	/*
	 * SDIO cards only define an upper 1 s limit on access.
	 */
	if (mmc_card_sdio(card)) {
		data->timeout_ns = 1000000000;
		data->timeout_clks = 0;
		return;
	}

	/*
	 * SD cards use a 100 multiplier rather than 10
	 */
	mult = mmc_card_sd(card) ? 100 : 10;

	/*
	 * Scale up the multiplier (and therefore the timeout) by
	 * the r2w factor for writes.
	 */
	if (data->flags & MMC_DATA_WRITE)
		mult <<= card->csd.r2w_factor;

	data->timeout_ns = card->csd.tacc_ns * mult;
	data->timeout_clks = card->csd.tacc_clks * mult;

	/*
	 * SD cards also have an upper limit on the timeout.
	 */
	if (mmc_card_sd(card)) {
		unsigned int timeout_us, limit_us;

		timeout_us = data->timeout_ns / 1000;
		timeout_us += data->timeout_clks * 1000 /
			(card->host->ios.clock / 1000);

		if (data->flags & MMC_DATA_WRITE)
			/*
			 * The limit is really 250 ms, but that is
			 * insufficient for some crappy cards.
			 */
			limit_us = 300000;
		else
			limit_us = 100000;

		/*
		 * SDHC cards always use these fixed values.
		 */
		if (timeout_us > limit_us || mmc_card_blockaddr(card)) {
			data->timeout_ns = limit_us * 1000;
			data->timeout_clks = 0;
		}
	}
	/*
	 * Some cards need very high timeouts if driven in SPI mode.
	 * The worst observed timeout was 900ms after writing a
	 * continuous stream of data until the internal logic
	 * overflowed.
	 */
	if (mmc_host_is_spi(card->host)) {
		if (data->flags & MMC_DATA_WRITE) {
			if (data->timeout_ns < 1000000000)
				data->timeout_ns = 1000000000;	/* 1s */
		} else {
			if (data->timeout_ns < 100000000)
				data->timeout_ns =  100000000;	/* 100ms */
		}
	}
}
EXPORT_SYMBOL(mmc_set_data_timeout);

/**
 *	mmc_align_data_size - pads a transfer size to a more optimal value
 *	@card: the MMC card associated with the data transfer
 *	@sz: original transfer size
 *
 *	Pads the original data size with a number of extra bytes in
 *	order to avoid controller bugs and/or performance hits
 *	(e.g. some controllers revert to PIO for certain sizes).
 *
 *	Returns the improved size, which might be unmodified.
 *
 *	Note that this function is only relevant when issuing a
 *	single scatter gather entry.
 */
unsigned int mmc_align_data_size(struct mmc_card *card, unsigned int sz)
{
	/*
	 * FIXME: We don't have a system for the controller to tell
	 * the core about its problems yet, so for now we just 32-bit
	 * align the size.
	 */
	sz = ((sz + 3) / 4) * 4;

	return sz;
}
EXPORT_SYMBOL(mmc_align_data_size);

/**
 *	mmc_host_enable - enable a host.
 *	@host: mmc host to enable
 *
 *	Hosts that support power saving can use the 'enable' and 'disable'
 *	methods to exit and enter power saving states. For more information
 *	see comments for struct mmc_host_ops.
 */
int mmc_host_enable(struct mmc_host *host)
{
	if (!(host->caps & MMC_CAP_DISABLE))
		return 0;

	if (host->en_dis_recurs)
		return 0;

	if (host->nesting_cnt++)
		return 0;

	cancel_delayed_work_sync(&host->disable);

	if (host->enabled)
		return 0;

	if (host->ops->enable) {
		int err;

		host->en_dis_recurs = 1;
		err = host->ops->enable(host);
		host->en_dis_recurs = 0;

		if (err) {
			pr_debug("%s: enable error %d\n",
				 mmc_hostname(host), err);
			return err;
		}
	}
	host->enabled = 1;
	return 0;
}
EXPORT_SYMBOL(mmc_host_enable);

static int mmc_host_do_disable(struct mmc_host *host, int lazy)
{
	if (host->ops->disable) {
		int err;

		host->en_dis_recurs = 1;
		err = host->ops->disable(host, lazy);
		host->en_dis_recurs = 0;

		if (err < 0) {
			pr_debug("%s: disable error %d\n",
				 mmc_hostname(host), err);
			return err;
		}
		if (err > 0) {
			unsigned long delay = msecs_to_jiffies(err);

			mmc_schedule_delayed_work(&host->disable, delay);
		}
	}
	host->enabled = 0;
	return 0;
}

/**
 *	mmc_host_disable - disable a host.
 *	@host: mmc host to disable
 *
 *	Hosts that support power saving can use the 'enable' and 'disable'
 *	methods to exit and enter power saving states. For more information
 *	see comments for struct mmc_host_ops.
 */
int mmc_host_disable(struct mmc_host *host)
{
	int err;

	if (!(host->caps & MMC_CAP_DISABLE))
		return 0;

	if (host->en_dis_recurs)
		return 0;

	if (--host->nesting_cnt)
		return 0;

	if (!host->enabled)
		return 0;

	err = mmc_host_do_disable(host, 0);
	return err;
}
EXPORT_SYMBOL(mmc_host_disable);

/**
 *	__mmc_claim_host - exclusively claim a host
 *	@host: mmc host to claim
 *	@abort: whether or not the operation should be aborted
 *
 *	Claim a host for a set of operations.  If @abort is non null and
 *	dereference a non-zero value then this will return prematurely with
 *	that non-zero value without acquiring the lock.  Returns zero
 *	with the lock held otherwise.
 */
int __mmc_claim_host(struct mmc_host *host, atomic_t *abort)
{
	DECLARE_WAITQUEUE(wait, current);
	unsigned long flags;
	int stop;

	might_sleep();

	add_wait_queue(&host->wq, &wait);
	spin_lock_irqsave(&host->lock, flags);
	while (1) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		stop = abort ? atomic_read(abort) : 0;
		if (stop || !host->claimed || host->claimer == current)
			break;
		spin_unlock_irqrestore(&host->lock, flags);
		schedule();
		spin_lock_irqsave(&host->lock, flags);
	}
	set_current_state(TASK_RUNNING);
	if (!stop) {
		host->claimed = 1;
		host->claimer = current;
		host->claim_cnt += 1;
	} else
		wake_up(&host->wq);
	spin_unlock_irqrestore(&host->lock, flags);
	remove_wait_queue(&host->wq, &wait);
	if (!stop)
		mmc_host_enable(host);
	return stop;
}

EXPORT_SYMBOL(__mmc_claim_host);

/**
 *	mmc_try_claim_host - try exclusively to claim a host
 *	@host: mmc host to claim
 *
 *	Returns %1 if the host is claimed, %0 otherwise.
 */
int mmc_try_claim_host(struct mmc_host *host)
{
	int claimed_host = 0;
	unsigned long flags;

	spin_lock_irqsave(&host->lock, flags);
	if (!host->claimed || host->claimer == current) {
		host->claimed = 1;
		host->claimer = current;
		host->claim_cnt += 1;
		claimed_host = 1;
	}
	spin_unlock_irqrestore(&host->lock, flags);
	return claimed_host;
}
EXPORT_SYMBOL(mmc_try_claim_host);

static void mmc_do_release_host(struct mmc_host *host)
{
	unsigned long flags;

	spin_lock_irqsave(&host->lock, flags);
	if (--host->claim_cnt) {
		/* Release for nested claim */
		spin_unlock_irqrestore(&host->lock, flags);
	} else {
		host->claimed = 0;
		host->claimer = NULL;
		spin_unlock_irqrestore(&host->lock, flags);
		wake_up(&host->wq);
	}
}

void mmc_host_deeper_disable(struct work_struct *work)
{
	struct mmc_host *host =
		container_of(work, struct mmc_host, disable.work);

	/* If the host is claimed then we do not want to disable it anymore */
	if (!mmc_try_claim_host(host))
		return;
	mmc_host_do_disable(host, 1);
	mmc_do_release_host(host);
}

/**
 *	mmc_host_lazy_disable - lazily disable a host.
 *	@host: mmc host to disable
 *
 *	Hosts that support power saving can use the 'enable' and 'disable'
 *	methods to exit and enter power saving states. For more information
 *	see comments for struct mmc_host_ops.
 */
int mmc_host_lazy_disable(struct mmc_host *host)
{
	if (!(host->caps & MMC_CAP_DISABLE))
		return 0;

	if (host->en_dis_recurs)
		return 0;

	if (--host->nesting_cnt)
		return 0;

	if (!host->enabled)
		return 0;

	if (host->disable_delay) {
		mmc_schedule_delayed_work(&host->disable,
				msecs_to_jiffies(host->disable_delay));
		return 0;
	} else
		return mmc_host_do_disable(host, 1);
}
EXPORT_SYMBOL(mmc_host_lazy_disable);

/**
 *	mmc_release_host - release a host
 *	@host: mmc host to release
 *
 *	Release a MMC host, allowing others to claim the host
 *	for their operations.
 */
void mmc_release_host(struct mmc_host *host)
{
	WARN_ON(!host->claimed);

	mmc_host_lazy_disable(host);

	mmc_do_release_host(host);
}

EXPORT_SYMBOL(mmc_release_host);

/*
 * Internal function that does the actual ios call to the host driver,
 * optionally printing some debug output.
 */
static inline void mmc_set_ios(struct mmc_host *host)
{
	struct mmc_ios *ios = &host->ios;

	pr_debug("%s: clock %uHz busmode %u powermode %u cs %u Vdd %u "
		"width %u timing %u\n",
		 mmc_hostname(host), ios->clock, ios->bus_mode,
		 ios->power_mode, ios->chip_select, ios->vdd,
		 ios->bus_width, ios->timing);

	host->ops->set_ios(host, ios);
}

/*
 * Control chip select pin on a host.
 */
void mmc_set_chip_select(struct mmc_host *host, int mode)
{
	host->ios.chip_select = mode;
	mmc_set_ios(host);
}

/*
 * Sets the host clock to the highest possible frequency that
 * is below "hz".
 */
void mmc_set_clock(struct mmc_host *host, unsigned int hz)
{
	WARN_ON(hz < host->f_min);

	if (hz > host->f_max)
		hz = host->f_max;

	host->ios.clock = hz;
	mmc_set_ios(host);
}

/*
 * Change the bus mode (open drain/push-pull) of a host.
 */
void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode)
{
	host->ios.bus_mode = mode;
	mmc_set_ios(host);
}

/*
 * Change data bus width of a host.
 */
void mmc_set_bus_width(struct mmc_host *host, unsigned int width)
{
	host->ios.bus_width = width;
	mmc_set_ios(host);
}

/**
 * mmc_vdd_to_ocrbitnum - Convert a voltage to the OCR bit number
 * @vdd:	voltage (mV)
 * @low_bits:	prefer low bits in boundary cases
 *
 * This function returns the OCR bit number according to the provided @vdd
 * value. If conversion is not possible a negative errno value returned.
 *
 * Depending on the @low_bits flag the function prefers low or high OCR bits
 * on boundary voltages. For example,
 * with @low_bits = true, 3300 mV translates to ilog2(MMC_VDD_32_33);
 * with @low_bits = false, 3300 mV translates to ilog2(MMC_VDD_33_34);
 *
 * Any value in the [1951:1999] range translates to the ilog2(MMC_VDD_20_21).
 */
static int mmc_vdd_to_ocrbitnum(int vdd, bool low_bits)
{
	const int max_bit = ilog2(MMC_VDD_35_36);
	int bit;

	if (vdd < 1650 || vdd > 3600)
		return -EINVAL;

	if (vdd >= 1650 && vdd <= 1950)
		return ilog2(MMC_VDD_165_195);

	if (low_bits)
		vdd -= 1;

	/* Base 2000 mV, step 100 mV, bit's base 8. */
	bit = (vdd - 2000) / 100 + 8;
	if (bit > max_bit)
		return max_bit;
	return bit;
}

/**
 * mmc_vddrange_to_ocrmask - Convert a voltage range to the OCR mask
 * @vdd_min:	minimum voltage value (mV)
 * @vdd_max:	maximum voltage value (mV)
 *
 * This function returns the OCR mask bits according to the provided @vdd_min
 * and @vdd_max values. If conversion is not possible the function returns 0.
 *
 * Notes wrt boundary cases:
 * This function sets the OCR bits for all boundary voltages, for example
 * [3300:3400] range is translated to MMC_VDD_32_33 | MMC_VDD_33_34 |
 * MMC_VDD_34_35 mask.
 */
u32 mmc_vddrange_to_ocrmask(int vdd_min, int vdd_max)
{
	u32 mask = 0;

	if (vdd_max < vdd_min)
		return 0;

	/* Prefer high bits for the boundary vdd_max values. */
	vdd_max = mmc_vdd_to_ocrbitnum(vdd_max, false);
	if (vdd_max < 0)
		return 0;

	/* Prefer low bits for the boundary vdd_min values. */
	vdd_min = mmc_vdd_to_ocrbitnum(vdd_min, true);
	if (vdd_min < 0)
		return 0;

	/* Fill the mask, from max bit to min bit. */
	while (vdd_max >= vdd_min)
		mask |= 1 << vdd_max--;

	return mask;
}
EXPORT_SYMBOL(mmc_vddrange_to_ocrmask);

#ifdef CONFIG_REGULATOR

/**
 * mmc_regulator_get_ocrmask - return mask of supported voltages
 * @supply: regulator to use
 *
 * This returns either a negative errno, or a mask of voltages that
 * can be provided to MMC/SD/SDIO devices using the specified voltage
 * regulator.  This would normally be called before registering the
 * MMC host adapter.
 */
int mmc_regulator_get_ocrmask(struct regulator *supply)
{
	int			result = 0;
	int			count;
	int			i;

	count = regulator_count_voltages(supply);
	if (count < 0)
		return count;

	for (i = 0; i < count; i++) {
		int		vdd_uV;
		int		vdd_mV;

		vdd_uV = regulator_list_voltage(supply, i);
		if (vdd_uV <= 0)
			continue;

		vdd_mV = vdd_uV / 1000;
		result |= mmc_vddrange_to_ocrmask(vdd_mV, vdd_mV);
	}

	return result;
}
EXPORT_SYMBOL(mmc_regulator_get_ocrmask);

/**
 * mmc_regulator_set_ocr - set regulator to match host->ios voltage
 * @vdd_bit: zero for power off, else a bit number (host->ios.vdd)
 * @supply: regulator to use
 *
 * Returns zero on success, else negative errno.
 *
 * MMC host drivers may use this to enable or disable a regulator using
 * a particular supply voltage.  This would normally be called from the
 * set_ios() method.
 */
int mmc_regulator_set_ocr(struct regulator *supply, unsigned short vdd_bit)
{
	int			result = 0;
	int			min_uV, max_uV;
	int			enabled;

	enabled = regulator_is_enabled(supply);
	if (enabled < 0)
		return enabled;

	if (vdd_bit) {
		int		tmp;
		int		voltage;

		/* REVISIT mmc_vddrange_to_ocrmask() may have set some
		 * bits this regulator doesn't quite support ... don't
		 * be too picky, most cards and regulators are OK with
		 * a 0.1V range goof (it's a small error percentage).
		 */
		tmp = vdd_bit - ilog2(MMC_VDD_165_195);
		if (tmp == 0) {
			min_uV = 1650 * 1000;
			max_uV = 1950 * 1000;
		} else {
			min_uV = 1900 * 1000 + tmp * 100 * 1000;
			max_uV = min_uV + 100 * 1000;
		}

		/* avoid needless changes to this voltage; the regulator
		 * might not allow this operation
		 */
		voltage = regulator_get_voltage(supply);
		if (voltage < 0)
			result = voltage;
		else if (voltage < min_uV || voltage > max_uV)
			result = regulator_set_voltage(supply, min_uV, max_uV);
		else
			result = 0;

		if (result == 0 && !enabled)
			result = regulator_enable(supply);
	} else if (enabled) {
		result = regulator_disable(supply);
	}

	return result;
}
EXPORT_SYMBOL(mmc_regulator_set_ocr);

#endif

/*
 * Mask off any voltages we don't support and select
 * the lowest voltage
 */
u32 mmc_select_voltage(struct mmc_host *host, u32 ocr)
{
	int bit;

	ocr &= host->ocr_avail;

	bit = ffs(ocr);
	if (bit) {
		bit -= 1;

		ocr &= 3 << bit;

		host->ios.vdd = bit;
		mmc_set_ios(host);
	} else {
		pr_warning("%s: host doesn't support card's voltages\n",
				mmc_hostname(host));
		ocr = 0;
	}

	return ocr;
}

/*
 * Select timing parameters for host.
 */
void mmc_set_timing(struct mmc_host *host, unsigned int timing)
{
	host->ios.timing = timing;
	mmc_set_ios(host);
}

/*
 * Apply power to the MMC stack.  This is a two-stage process.
 * First, we enable power to the card without the clock running.
 * We then wait a bit for the power to stabilise.  Finally,
 * enable the bus drivers and clock to the card.
 *
 * We must _NOT_ enable the clock prior to power stablising.
 *
 * If a host does all the power sequencing itself, ignore the
 * initial MMC_POWER_UP stage.
 */
static void mmc_power_up(struct mmc_host *host)
{
	int bit;

	/* If ocr is set, we use it */
	if (host->ocr)
		bit = ffs(host->ocr) - 1;
	else
		bit = fls(host->ocr_avail) - 1;

	host->ios.vdd = bit;
	if (mmc_host_is_spi(host)) {
		host->ios.chip_select = MMC_CS_HIGH;
		host->ios.bus_mode = MMC_BUSMODE_PUSHPULL;
	} else {
		host->ios.chip_select = MMC_CS_DONTCARE;
		host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
	}
	host->ios.power_mode = MMC_POWER_UP;
	host->ios.bus_width = MMC_BUS_WIDTH_1;
	host->ios.timing = MMC_TIMING_LEGACY;
	mmc_set_ios(host);

	/*
	 * This delay should be sufficient to allow the power supply
	 * to reach the minimum voltage.
	 */
	mmc_delay(10);

	if (host->f_min > 400000) {
		pr_warning("%s: Minimum clock frequency too high for "
				"identification mode\n", mmc_hostname(host));
		host->ios.clock = host->f_min;
	} else
		host->ios.clock = 400000;

	host->ios.power_mode = MMC_POWER_ON;
	mmc_set_ios(host);

	/*
	 * This delay must be at least 74 clock sizes, or 1 ms, or the
	 * time required to reach a stable voltage.
	 */
	mmc_delay(10);
}

static void mmc_power_off(struct mmc_host *host)
{
	host->ios.clock = 0;
	host->ios.vdd = 0;
	if (!mmc_host_is_spi(host)) {
		host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
		host->ios.chip_select = MMC_CS_DONTCARE;
	}
	host->ios.power_mode = MMC_POWER_OFF;
	host->ios.bus_width = MMC_BUS_WIDTH_1;
	host->ios.timing = MMC_TIMING_LEGACY;
	mmc_set_ios(host);
}

/*
 * Cleanup when the last reference to the bus operator is dropped.
 */
static void __mmc_release_bus(struct mmc_host *host)
{
	BUG_ON(!host);
	BUG_ON(host->bus_refs);
	BUG_ON(!host->bus_dead);

	host->bus_ops = NULL;
}

/*
 * Increase reference count of bus operator
 */
static inline void mmc_bus_get(struct mmc_host *host)
{
	unsigned long flags;

	spin_lock_irqsave(&host->lock, flags);
	host->bus_refs++;
	spin_unlock_irqrestore(&host->lock, flags);
}

/*
 * Decrease reference count of bus operator and free it if
 * it is the last reference.
 */
static inline void mmc_bus_put(struct mmc_host *host)
{
	unsigned long flags;

	spin_lock_irqsave(&host->lock, flags);
	host->bus_refs--;
	if ((host->bus_refs == 0) && host->bus_ops)
		__mmc_release_bus(host);
	spin_unlock_irqrestore(&host->lock, flags);
}

/*
 * Assign a mmc bus handler to a host. Only one bus handler may control a
 * host at any given time.
 */
void mmc_attach_bus(struct mmc_host *host, const struct mmc_bus_ops *ops)
{
	unsigned long flags;

	BUG_ON(!host);
	BUG_ON(!ops);

	WARN_ON(!host->claimed);

	spin_lock_irqsave(&host->lock, flags);

	BUG_ON(host->bus_ops);
	BUG_ON(host->bus_refs);

	host->bus_ops = ops;
	host->bus_refs = 1;
	host->bus_dead = 0;

	spin_unlock_irqrestore(&host->lock, flags);
}

/*
 * Remove the current bus handler from a host. Assumes that there are
 * no interesting cards left, so the bus is powered down.
 */
void mmc_detach_bus(struct mmc_host *host)
{
	unsigned long flags;

	BUG_ON(!host);

	WARN_ON(!host->claimed);
	WARN_ON(!host->bus_ops);

	spin_lock_irqsave(&host->lock, flags);

	host->bus_dead = 1;

	spin_unlock_irqrestore(&host->lock, flags);

	mmc_power_off(host);

	mmc_bus_put(host);
}

/**
 *	mmc_detect_change - process change of state on a MMC socket
 *	@host: host which changed state.
 *	@delay: optional delay to wait before detection (jiffies)
 *
 *	MMC drivers should call this when they detect a card has been
 *	inserted or removed. The MMC layer will confirm that any
 *	present card is still functional, and initialize any newly
 *	inserted.
 */
void mmc_detect_change(struct mmc_host *host, unsigned long delay)
{
#ifdef CONFIG_MMC_DEBUG
	unsigned long flags;
	spin_lock_irqsave(&host->lock, flags);
	WARN_ON(host->removed);
	spin_unlock_irqrestore(&host->lock, flags);
#endif

	mmc_schedule_delayed_work(&host->detect, delay);
}

EXPORT_SYMBOL(mmc_detect_change);


void mmc_rescan(struct work_struct *work)
{
	struct mmc_host *host =
		container_of(work, struct mmc_host, detect.work);
	u32 ocr;
	int err;

	mmc_bus_get(host);

	/* if there is a card registered, check whether it is still present */
	if ((host->bus_ops != NULL) && host->bus_ops->detect && !host->bus_dead)
		host->bus_ops->detect(host);

	mmc_bus_put(host);


	mmc_bus_get(host);

	/* if there still is a card present, stop here */
	if (host->bus_ops != NULL) {
		mmc_bus_put(host);
		goto out;
	}

	/* detect a newly inserted card */

	/*
	 * Only we can add a new handler, so it's safe to
	 * release the lock here.
	 */
	mmc_bus_put(host);

	if (host->ops->get_cd && host->ops->get_cd(host) == 0)
		goto out;

	mmc_claim_host(host);

	mmc_power_up(host);
	mmc_go_idle(host);

	mmc_send_if_cond(host, host->ocr_avail);

	/*
	 * First we search for SDIO...
	 */
	err = mmc_send_io_op_cond(host, 0, &ocr);
	if (!err) {
		if (mmc_attach_sdio(host, ocr))
			mmc_power_off(host);
		goto out;
	}

	/*
	 * ...then normal SD...
	 */
	err = mmc_send_app_op_cond(host, 0, &ocr);
	if (!err) {
		if (mmc_attach_sd(host, ocr))
			mmc_power_off(host);
		goto out;
	}

	/*
	 * ...and finally MMC.
	 */
	err = mmc_send_op_cond(host, 0, &ocr);
	if (!err) {
		if (mmc_attach_mmc(host, ocr))
			mmc_power_off(host);
		goto out;
	}

	mmc_release_host(host);
	mmc_power_off(host);

out:
	if (host->caps & MMC_CAP_NEEDS_POLL)
		mmc_schedule_delayed_work(&host->detect, HZ);
}

void mmc_start_host(struct mmc_host *host)
{
	mmc_power_off(host);
	mmc_detect_change(host, 0);
}

void mmc_stop_host(struct mmc_host *host)
{
#ifdef CONFIG_MMC_DEBUG
	unsigned long flags;
	spin_lock_irqsave(&host->lock, flags);
	host->removed = 1;
	spin_unlock_irqrestore(&host->lock, flags);
#endif

	if (host->caps & MMC_CAP_DISABLE)
		cancel_delayed_work(&host->disable);
	cancel_delayed_work(&host->detect);
	mmc_flush_scheduled_work();

	mmc_bus_get(host);
	if (host->bus_ops && !host->bus_dead) {
		if (host->bus_ops->remove)
			host->bus_ops->remove(host);

		mmc_claim_host(host);
		mmc_detach_bus(host);
		mmc_release_host(host);
		mmc_bus_put(host);
		return;
	}
	mmc_bus_put(host);

	BUG_ON(host->card);

	mmc_power_off(host);
}

void mmc_power_save_host(struct mmc_host *host)
{
	mmc_bus_get(host);

	if (!host->bus_ops || host->bus_dead || !host->bus_ops->power_restore) {
		mmc_bus_put(host);
		return;
	}

	if (host->bus_ops->power_save)
		host->bus_ops->power_save(host);

	mmc_bus_put(host);

	mmc_power_off(host);
}
EXPORT_SYMBOL(mmc_power_save_host);

void mmc_power_restore_host(struct mmc_host *host)
{
	mmc_bus_get(host);

	if (!host->bus_ops || host->bus_dead || !host->bus_ops->power_restore) {
		mmc_bus_put(host);
		return;
	}

	mmc_power_up(host);
	host->bus_ops->power_restore(host);

	mmc_bus_put(host);
}
EXPORT_SYMBOL(mmc_power_restore_host);

int mmc_card_awake(struct mmc_host *host)
{
	int err = -ENOSYS;

	mmc_bus_get(host);

	if (host->bus_ops && !host->bus_dead && host->bus_ops->awake)
		err = host->bus_ops->awake(host);

	mmc_bus_put(host);

	return err;
}
EXPORT_SYMBOL(mmc_card_awake);

int mmc_card_sleep(struct mmc_host *host)
{
	int err = -ENOSYS;

	mmc_bus_get(host);

	if (host->bus_ops && !host->bus_dead && host->bus_ops->awake)
		err = host->bus_ops->sleep(host);

	mmc_bus_put(host);

	return err;
}
EXPORT_SYMBOL(mmc_card_sleep);

int mmc_card_can_sleep(struct mmc_host *host)
{
	struct mmc_card *card = host->card;

	if (card && mmc_card_mmc(card) && card->ext_csd.rev >= 3)
		return 1;
	return 0;
}
EXPORT_SYMBOL(mmc_card_can_sleep);

#ifdef CONFIG_PM

/**
 *	mmc_suspend_host - suspend a host
 *	@host: mmc host
 *	@state: suspend mode (PM_SUSPEND_xxx)
 */
int mmc_suspend_host(struct mmc_host *host, pm_message_t state)
{
	int err = 0;

	if (host->caps & MMC_CAP_DISABLE)
		cancel_delayed_work(&host->disable);
	cancel_delayed_work(&host->detect);
	mmc_flush_scheduled_work();

	mmc_bus_get(host);
	if (host->bus_ops && !host->bus_dead) {
		if (host->bus_ops->suspend)
			err = host->bus_ops->suspend(host);
		if (err == -ENOSYS || !host->bus_ops->resume) {
			/*
			 * We simply "remove" the card in this case.
			 * It will be redetected on resume.
			 */
			if (host->bus_ops->remove)
				host->bus_ops->remove(host);
			mmc_claim_host(host);
			mmc_detach_bus(host);
			mmc_release_host(host);
			err = 0;
		}
	}
	mmc_bus_put(host);

	if (!err)
		mmc_power_off(host);

	return err;
}

EXPORT_SYMBOL(mmc_suspend_host);

/**
 *	mmc_resume_host - resume a previously suspended host
 *	@host: mmc host
 */
int mmc_resume_host(struct mmc_host *host)
{
	int err = 0;

	mmc_bus_get(host);
	if (host->bus_ops && !host->bus_dead) {
		mmc_power_up(host);
		mmc_select_voltage(host, host->ocr);
		BUG_ON(!host->bus_ops->resume);
		err = host->bus_ops->resume(host);
		if (err) {
			printk(KERN_WARNING "%s: error %d during resume "
					    "(card was removed?)\n",
					    mmc_hostname(host), err);
			if (host->bus_ops->remove)
				host->bus_ops->remove(host);
			mmc_claim_host(host);
			mmc_detach_bus(host);
			mmc_release_host(host);
			/* no need to bother upper layers */
			err = 0;
		}
	}
	mmc_bus_put(host);

	/*
	 * We add a slight delay here so that resume can progress
	 * in parallel.
	 */
	mmc_detect_change(host, 1);

	return err;
}

EXPORT_SYMBOL(mmc_resume_host);

#endif

static int __init mmc_init(void)
{
	int ret;

	workqueue = create_singlethread_workqueue("kmmcd");
	if (!workqueue)
		return -ENOMEM;

	ret = mmc_register_bus();
	if (ret)
		goto destroy_workqueue;

	ret = mmc_register_host_class();
	if (ret)
		goto unregister_bus;

	ret = sdio_register_bus();
	if (ret)
		goto unregister_host_class;

	return 0;

unregister_host_class:
	mmc_unregister_host_class();
unregister_bus:
	mmc_unregister_bus();
destroy_workqueue:
	destroy_workqueue(workqueue);

	return ret;
}

static void __exit mmc_exit(void)
{
	sdio_unregister_bus();
	mmc_unregister_host_class();
	mmc_unregister_bus();
	destroy_workqueue(workqueue);
}

subsys_initcall(mmc_init);
module_exit(mmc_exit);

MODULE_LICENSE("GPL");