path: root/drivers/mtd/nand/docg4.c

/*
 *  Copyright © 2012 Mike Dunn <mikedunn@newsguy.com>
 *
 * mtd nand driver for M-Systems DiskOnChip G4
 *
 * 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.
 *
 * Tested on the Palm Treo 680.  The G4 is also present on Toshiba Portege, Asus
 * P526, some HTC smartphones (Wizard, Prophet, ...), O2 XDA Zinc, maybe others.
 * Should work on these as well.  Let me know!
 *
 * TODO:
 *
 *  Mechanism for management of password-protected areas
 *
 *  Hamming ecc when reading oob only
 *
 *  According to the M-Sys documentation, this device is also available in a
 *  "dual-die" configuration having a 256MB capacity, but no mechanism for
 *  detecting this variant is documented.  Currently this driver assumes 128MB
 *  capacity.
 *
 *  Support for multiple cascaded devices ("floors").  Not sure which gadgets
 *  contain multiple G4s in a cascaded configuration, if any.
 *
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/export.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/bitops.h>
#include <linux/mtd/partitions.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/bch.h>
#include <linux/bitrev.h>

/*
 * In "reliable mode" consecutive 2k pages are used in parallel (in some
 * fashion) to store the same data.  The data can be read back from the
 * even-numbered pages in the normal manner; odd-numbered pages will appear to
 * contain junk.  Systems that boot from the docg4 typically write the secondary
 * program loader (SPL) code in this mode.  The SPL is loaded by the initial
 * program loader (IPL, stored in the docg4's 2k NOR-like region that is mapped
 * to the reset vector address).  This module parameter enables you to use this
 * driver to write the SPL.  When in this mode, no more than 2k of data can be
 * written at a time, because the addresses do not increment in the normal
 * manner, and the starting offset must be within an even-numbered 2k region;
 * i.e., invalid starting offsets are 0x800, 0xa00, 0xc00, 0xe00, 0x1800,
 * 0x1a00, ...  Reliable mode is a special case and should not be used unless
 * you know what you're doing.
 */
static bool reliable_mode;
module_param(reliable_mode, bool, 0);
MODULE_PARM_DESC(reliable_mode, "pages are programmed in reliable mode");

/*
 * You'll want to ignore badblocks if you're reading a partition that contains
 * data written by the TrueFFS library (i.e., by PalmOS, Windows, etc), since
 * it does not use mtd nand's method for marking bad blocks (using oob area).
 * This will also skip the check of the "page written" flag.
 */
static bool ignore_badblocks;
module_param(ignore_badblocks, bool, 0);
MODULE_PARM_DESC(ignore_badblocks, "no badblock checking performed");

struct docg4_priv {
	struct mtd_info	*mtd;
	struct device *dev;
	void __iomem *virtadr;
	int status;
	struct {
		unsigned int command;
		int column;
		int page;
	} last_command