path: root/drivers/mtd/devices/docg3.c

/*
 * Handles the M-Systems DiskOnChip G3 chip
 *
 * Copyright (C) 2011 Robert Jarzmik
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/platform_device.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>

#include <linux/debugfs.h>
#include <linux/seq_file.h>

#define CREATE_TRACE_POINTS
#include "docg3.h"

/*
 * This driver handles the DiskOnChip G3 flash memory.
 *
 * As no specification is available from M-Systems/Sandisk, this drivers lacks
 * several functions available on the chip, as :
 *  - block erase
 *  - page write
 *  - IPL write
 *  - ECC fixing (lack of BCH algorith understanding)
 *  - powerdown / powerup
 *
 * The bus data width (8bits versus 16bits) is not handled (if_cfg flag), and
 * the driver assumes a 16bits data bus.
 *
 * DocG3 relies on 2 ECC algorithms, which are handled in hardware :
 *  - a 1 byte Hamming code stored in the OOB for each page
 *  - a 7 bytes BCH code stored in the OOB for each page
 * The BCH part is only used for check purpose, no correction is available as
 * some information is missing. What is known is that :
 *  - BCH is in GF(2^14)
 *  - BCH is over data of 520 bytes (512 page + 7 page_info bytes
 *                                   + 1 hamming byte)
 *  - BCH can correct up to 4 bits (t = 4)
 *  - BCH syndroms are calculated in hardware, and checked in hardware as well
 *
 */

static inline u8 doc_readb(struct docg3 *docg3, u16 reg)
{
	u8 val = readb(docg3->base + reg);

	trace_docg3_io(0, 8, reg, (int)val);
	return val;
}

static inline u16 doc_readw(struct docg3 *docg3, u16 reg)
{
	u16 val = readw(docg3->base + reg);

	trace_docg3_io(0, 16, reg, (int)val);
	return val;
}

static inline void doc_writeb(struct docg3 *docg3, u8 val, u16 reg)
{
	writeb(val, docg3->base + reg);
	trace_docg3_io(1, 16, reg, val);
}

static inline void doc_writew(struct docg3 *docg3, u16 val, u16 reg)
{
	writew(val, docg3->base + reg);
	trace_docg3_io(1, 16, reg, val);
}

static inline void doc_flash_command(struct docg3 *docg3, u8 cmd)
{
	doc_writeb(docg3, cmd, DOC_FLASHCOMMAND);
}

static inline void doc_flash_sequence(struct docg3 *docg3, u8 seq)
{
	doc_writeb(docg3, seq, DOC_FLASHSEQUENCE);
}

static inline void doc_flash_address(struct docg3 *docg3, u8 addr)
{
	doc_writeb(docg3, addr, DOC_FLASHADDRESS);
}

static char const *part_probes[] = { "cmdlinepart", "saftlpart", NULL };

static int doc_register_readb(struct docg3 *docg3, int reg)
{
	u8 val;

	doc_writew(docg3, reg, DOC_READADDRESS);
	val = doc_readb(docg3, reg);
	doc_vdbg("Read register %04x : %02x\n", reg, val);
	return val;
}

static int doc_register_readw(struct docg3 *docg3, int reg)
{
	u16 val;

	doc_writew(docg3, reg, DOC_READADDRESS);
	val = doc_readw(docg3, reg);
	doc_vdbg("Read register %04x : %04x\n", reg, val);
	return val;
}

/**
 * doc_delay - delay docg3 operations
 * @docg3: the device
 * @nbNOPs: the number of NOPs to issue
 *
 * As no specification is available, the right timings between chip commands are
 * unknown. The only available piece of information are the observed nops on a
 * working docg3 chip.
 * Therefore, doc_delay relies on a busy loop of NOPs, instead of scheduler
 * friendlier msleep() functions or blocking mdelay().
 */
static void doc_delay(struct docg3 *docg3, int nbNOPs)
{
	int i;

	doc_dbg("NOP x %d\n", nbNOPs);
	for (i