path: root/drivers/mmc/host/mmc_spi.c

/*
 * mmc_spi.c - Access SD/MMC cards through SPI master controllers
 *
 * (C) Copyright 2005, Intec Automation,
 *		Mike Lavender (mike@steroidmicros)
 * (C) Copyright 2006-2007, David Brownell
 * (C) Copyright 2007, Axis Communications,
 *		Hans-Peter Nilsson (hp@axis.com)
 * (C) Copyright 2007, ATRON electronic GmbH,
 *		Jan Nikitenko <jan.nikitenko@gmail.com>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/dma-mapping.h>
#include <linux/crc7.h>
#include <linux/crc-itu-t.h>
#include <linux/scatterlist.h>

#include <linux/mmc/host.h>
#include <linux/mmc/mmc.h>		/* for R1_SPI_* bit values */
#include <linux/mmc/slot-gpio.h>

#include <linux/spi/spi.h>
#include <linux/spi/mmc_spi.h>

#include <asm/unaligned.h>


/* NOTES:
 *
 * - For now, we won't try to interoperate with a real mmc/sd/sdio
 *   controller, although some of them do have hardware support for
 *   SPI protocol.  The main reason for such configs would be mmc-ish
 *   cards like DataFlash, which don't support that "native" protocol.
 *
 *   We don't have a "DataFlash/MMC/SD/SDIO card slot" abstraction to
 *   switch between driver stacks, and in any case if "native" mode
 *   is available, it will be faster and hence preferable.
 *
 * - MMC depends on a different chipselect management policy than the
 *   SPI interface currently supports for shared bus segments:  it needs
 *   to issue multiple spi_message requests with the chipselect active,
 *   using the results of one message to decide the next one to issue.
 *
 *   Pending updates to the programming interface, this driver expects
 *   that it not share the bus with other drivers (precluding conflicts).
 *
 * - We tell the controller to keep the chipselect active from the
 *   beginning of an mmc_host_ops.request until the end.  So beware
 *   of SPI controller drivers that mis-handle the cs_change flag!
 *
 *   However, many cards seem OK with chipselect flapping up/down
 *   during that time ... at least on unshared bus segments.
 */


/*
 * Local protocol constants, internal to data block protocols.
 */

/* Response tokens used to ack each block written: */
#define SPI_MMC_RESPONSE_CODE(x)	((x) & 0x1f)
#define SPI_RESPONSE_ACCEPTED		((2 << 1)|1)
#define SPI_RESPONSE_CRC_ERR		((5 << 1)|1)
#define SPI_RESPONSE_WRITE_ERR		((6 << 1)|1)

/* Read and write blocks start with these tokens and end with crc;
 * on error, read tokens act like a subset of R2_SPI_* values.
 */
#define SPI_TOKEN_SINGLE	0xfe	/* single block r/w, multiblock read */
#define SPI_TOKEN_MULTI_WRITE	0xfc	/* multiblock write */
#define SPI_TOKEN_STOP_TRAN	0xfd	/* terminate multiblock write */

#define MMC_SPI_BLOCKSIZE	512


/* These fixed timeouts come from the latest SD specs, which say to ignore
 * the CSD values.  The R1B value is for card erase (e.g. the "I forgot the
 * card's password" scenario); it's mostly applied to STOP_TRANSMISSION after
 * reads which takes nowhere near that long.  Older cards may be able to use
 * shorter timeouts ... but why bother?
 */
#define r1b_timeout		(HZ * 3)

/* One of the critical speed parameters is the amount of data which may
 * be transferred in one command. If this value is too low, the SD card
 * controller has to do multiple partial block writes (argggh!). With
 * today (2008) SD cards there is little speed gain if we transfer more
 * than 64 KBytes at a time. So use this value until there is any indication
 * that we should do more here.
 */
#define MMC_SPI_BLOCKSATONCE	128

/****************************************************************************/

/*
 * Local Data Structures
 */

/* "scratch" is per-{command,block} data exchanged with the card */
struct scratch {
	u8			status[29];
	u8			data_token;
	__be16			crc_val;
};

struct mmc_spi_host {
	struct mmc_host		*mmc;
	struct spi_device	*spi;

	unsigned char		power_mode;
	u16			powerup_msecs;

	struct mmc_spi_platform_data	*pdata;

	/* for bulk data transfers */
	struct spi_transfer	token, t, crc, early_status;
	struct spi_message	m;

	/* for status readback */
	struct spi_transfer	status;
	struct spi_message	readback;

	/* underlying DMA-aware controller, or null */
	struct device		*dma_dev;

	/* buffer used for commands and for message "overhead" */
	struct scratch		*data;
	dma_addr_t		data_dma;

	/* Specs say to write ones most of the time, even when the card
	 * has no need to read its input data; and many cards won't care.
	 * This is our source of those ones.
	 */
	void			*ones;
	dma_addr_t		ones_dma;
};


/****************************************************************************/

/*
 * MMC-over-SPI protocol glue, used by the MMC stack interface
 */

static inline int mmc_cs_off(struct mmc_spi_host *host)
{
	/* chipselect will always be inactive after setup() */
	return spi_setup(host->spi);
}

static int
mmc_spi_readbytes(struct mmc_spi_host *host, unsigned len)
{
	int status;

	if (len > sizeof(*host->data)) {
		WARN_ON(1);
		return -EIO;
	}

	host->status.len = len;

	if (host->dma_dev)
		dma_sync_single_for_device(host->dma_dev,
				host->data_dma, sizeof(*host->data),
				DMA_FROM_DEVICE);

	status = spi_sync_locked(host->spi, &host->readback);

	if (host->dma_dev)
		dma_sync_single_for_cpu(host->dma_dev,
				host->data_dma, sizeof(*host->data),
				DMA_FROM_DEVICE);

	return status;
}

static int mmc_spi_skip(struct mmc_spi_host *host, unsigned long timeout,
			unsigned n, u8 byte)
{
	u8		*cp = host->data->status;
	unsigned long start = jiffies;

	while (1) {
		int		status;
		unsigned	i;

		status = mmc_spi_readbytes(host, n);
		if (status < 0)
			return status;

		for (i = 0; i < n; i++) {
			if (cp[i] != byte)
				return cp[i];
		}

		if (time_is_before_jiffies(start + timeout))
			break;

		/* If we need long timeouts, we may release the CPU.
		 * We use jiffies here because we want to have a relation
		 * between elapsed time and the blocking of th