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/hrtimer.h>
#include <linux/delay.h>
#include <linux/blkdev.h>
#include <linux/dma-mapping.h>
#include <linux/crc7.h>
#include <linux/crc-itu-t.h>

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

#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 readblock_timeout	ktime_set(0, 100 * 1000 * 1000)
#define writeblock_timeout	ktime_set(0, 250 * 1000 * 1000)
#define r1b_timeout		ktime_set(3, 0)


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

/*
 * 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