mtd: sharpslpart: Add sharpslpart partition parser

The Sharp SL Series (Zaurus) PXA handhelds have 16/64/128M of NAND flash
and share the same layout of the first 7M partition, managed by Sharp FTL.

GPL 2.4 sources: http://support.ezaurus.com/developer/source/source_dl.asp

The purpose of this self-contained patch is to add a common parser and
remove the hardcoded sizes in the board files (these devices are not yet
converted to devicetree).
Users will have benefits because the mtdparts= tag will not be necessary
anymore and they will be free to repartition the little sized flash.

The obsolete bootloader can not pass the partitioning info to modern
kernels anymore so it has to be read from flash at known logical addresses.
(see http://www.h5.dion.ne.jp/~rimemoon/zaurus/memo_006.htm )

In kernel, under arch/arm/mach-pxa we have already 8 machines:
MACH_POODLE, MACH_CORGI, MACH_SHEPERD, MACH_HUSKY, MACH_AKITA, MACH_SPITZ,
MACH_BORZOI, MACH_TOSA.
Lost after the 2.4 vendor kernel are MACH_BOXER and MACH_TERRIER.

Almost every model has different factory partitioning: add to this the
units can be repartitioned by users with userspace tools (nandlogical)
and installers for popular (back then) linux distributions.

The Parameter Area in the first (boot) partition extends from 0x00040000 to
0x0007bfff (176k) and contains two copies of the partition table:
...
0x00060000: Partition Info1     16k
0x00064000: Partition Info2     16k
0x00668000: Model               16k
...

The first 7M partition is managed by the Sharp FTL reserving 5% + 1 blocks
for wear-leveling: some blocks are remapped and one layer of translation
(logical to physical) is necessary.

There isn't much documentation about this FTL in the 2.4 sources, just the
MTD methods for reading and writing using logical addresses and the block
management (wear-leveling, use counter).
It seems this FTL was tailored with 16KiB eraesize in mind so to fit one
param block exactly, to have two copies of the partition table on two
blocks.
Later pxa27x devices have same size but 128KiB erasesize and less blocks
(56 vs. 448) but the same schema was adopted, even if the two tables are
now in the same eraseblock.

For the purpose of the MTD parser only the read part of the code was taken.

The NAND drivers that can use this parser are sharpsl.c and tmio_nand.c.
Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

drivers/mtd/parsers/Kconfig

@@ -6,3 +6,11 @@ config MTD_PARSER_TRX
 	  may contain up to 3/4 partitions (depending on the version).
 	  This driver will parse TRX header and report at least two partitions:
 	  kernel and rootfs.
+
+config MTD_SHARPSL_PARTS
+	tristate "Sharp SL Series NAND flash partition parser"
+	depends on MTD_NAND_SHARPSL || MTD_NAND_TMIO || COMPILE_TEST
+	help
+	  This provides the read-only FTL logic necessary to read the partition
+	  table from the NAND flash of Sharp SL Series (Zaurus) and the MTD
+	  partition parser using this code.

drivers/mtd/parsers/Makefile

 obj-$(CONFIG_MTD_PARSER_TRX)		+= parser_trx.o
+obj-$(CONFIG_MTD_SHARPSL_PARTS)		+= sharpslpart.o

drivers/mtd/parsers/sharpslpart.c

+/*
+ * sharpslpart.c - MTD partition parser for NAND flash using the SHARP FTL
+ * for logical addressing, as used on the PXA models of the SHARP SL Series.
+ *
+ * Copyright (C) 2017 Andrea Adami <andrea.adami@gmail.com>
+ *
+ * Based on SHARP GPL 2.4 sources:
+ *   http://support.ezaurus.com/developer/source/source_dl.asp
+ *     drivers/mtd/nand/sharp_sl_logical.c
+ *     linux/include/asm-arm/sharp_nand_logical.h
+ *
+ * Copyright (C) 2002 SHARP
+ *
+ * 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.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/bitops.h>
+#include <linux/sizes.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+
+/* oob structure */
+#define NAND_NOOB_LOGADDR_00		8
+#define NAND_NOOB_LOGADDR_01		9
+#define NAND_NOOB_LOGADDR_10		10
+#define NAND_NOOB_LOGADDR_11		11
+#define NAND_NOOB_LOGADDR_20		12
+#define NAND_NOOB_LOGADDR_21		13
+
+#define BLOCK_IS_RESERVED		0xffff
+#define BLOCK_UNMASK_COMPLEMENT		1
+
+/* factory defaults */
+#define SHARPSL_NAND_PARTS		3
+#define SHARPSL_FTL_PART_SIZE		(7 * SZ_1M)
+#define SHARPSL_PARTINFO1_LADDR		0x00060000
+#define SHARPSL_PARTINFO2_LADDR		0x00064000
+
+#define BOOT_MAGIC			0x424f4f54
+#define FSRO_MAGIC			0x4653524f
+#define FSRW_MAGIC			0x46535257
+
+/**
+ * struct sharpsl_ftl - Sharp FTL Logical Table
+ * @logmax:		number of logical blocks
+ * @log2phy:		the logical-to-physical table
+ *
+ * Structure containing the logical-to-physical translation table
+ * used by the SHARP SL FTL.
+ */
+struct sharpsl_ftl {
+	unsigned int logmax;
+	unsigned int *log2phy;
+};
+
+/* verify that the OOB bytes 8 to 15 are free and available for the FTL */
+static int sharpsl_nand_check_ooblayout(struct mtd_info *mtd)
+{
+	u8 freebytes = 0;
+	int section = 0;
+
+	while (true) {
+		struct mtd_oob_region oobfree = { };
+		int ret, i;
+
+		ret = mtd_ooblayout_free(mtd, section++, &oobfree);
+		if (ret)
+			break;
+
+		if (!oobfree.length || oobfree.offset > 15 ||
+		    (oobfree.offset + oobfree.length) < 8)
+			continue;
+
+		i = oobfree.offset >= 8 ? oobfree.offset : 8;
+		for (; i < oobfree.offset + oobfree.length && i < 16; i++)
+			freebytes |= BIT(i - 8);
+
+		if (freebytes == 0xff)
+			return 0;
+	}
+
+	return -ENOTSUPP;
+}
+
+static int sharpsl_nand_read_oob(struct mtd_info *mtd, loff_t offs, u8 *buf)
+{
+	struct mtd_oob_ops ops = { };
+	int ret;
+
+	ops.mode = MTD_OPS_PLACE_OOB;
+	ops.ooblen = mtd->oobsize;
+	ops.oobbuf = buf;
+
+	ret = mtd_read_oob(mtd, offs, &ops);
+	if (ret != 0 || mtd->oobsize != ops.oobretlen)
+		return -1;
+
+	return 0;
+}
+
+/*
+ * The logical block number assigned to a physical block is stored in the OOB
+ * of the first page, in 3 16-bit copies with the following layout:
+ *
+ * 01234567 89abcdef
+ * -------- --------
+ * ECC BB   xyxyxy
+ *
+ * When reading we check that the first two copies agree.
+ * In case of error, matching is tried using the following pairs.
+ * Reserved values 0xffff mean the block is kept for wear leveling.
+ *
+ * 01234567 89abcdef
+ * -------- --------
+ * ECC BB   xyxy    oob[8]==oob[10] && oob[9]==oob[11]   -> byte0=8   byte1=9
+ * ECC BB     xyxy  oob[10]==oob[12] && oob[11]==oob[13] -> byte0=10  byte1=11
+ * ECC BB   xy  xy  oob[12]==oob[8] && oob[13]==oob[9]   -> byte0=12  byte1=13
+ */
+static int sharpsl_nand_get_logical_num(u8 *oob)
+{
+	u16 us;
+	int good0, good1;
+
+	if (oob[NAND_NOOB_LOGADDR_00] == oob[NAND_NOOB_LOGADDR_10] &&
+	    oob[NAND_NOOB_LOGADDR_01] == oob[NAND_NOOB_LOGADDR_11]) {
+		good0 = NAND_NOOB_LOGADDR_00;
+		good1 = NAND_NOOB_LOGADDR_01;
+	} else if (oob[NAND_NOOB_LOGADDR_10] == oob[NAND_NOOB_LOGADDR_20] &&
+		   oob[NAND_NOOB_LOGADDR_11] == oob[NAND_NOOB_LOGADDR_21]) {
+		good0 = NAND_NOOB_LOGADDR_10;
+		good1 = NAND_NOOB_LOGADDR_11;
+	} else if (oob[NAND_NOOB_LOGADDR_20] == oob[NAND_NOOB_LOGADDR_00] &&
+		   oob[NAND_NOOB_LOGADDR_21] == oob[NAND_NOOB_LOGADDR_01]) {
+		good0 = NAND_NOOB_LOGADDR_20;
+		good1 = NAND_NOOB_LOGADDR_21;
+	} else {
+		return -EINVAL;
+	}
+
+	us = oob[good0] | oob[good1] << 8;
+
+	/* parity check */
+	if (hweight16(us) & BLOCK_UNMASK_COMPLEMENT)
+		return -EINVAL;
+
+	/* reserved */
+	if (us == BLOCK_IS_RESERVED)
+		return BLOCK_IS_RESERVED;
+
+	return (us >> 1) & GENMASK(9, 0);
+}
+
+static int sharpsl_nand_init_ftl(struct mtd_info *mtd, struct sharpsl_ftl *ftl)
+{
+	unsigned int block_num, log_num, phymax;
+	loff_t block_adr;
+	u8 *oob;
+	int i, ret;
+
+	oob = kzalloc(mtd->oobsize, GFP_KERNEL);
+	if (!oob)
+		return -ENOMEM;
+
+	phymax = mtd_div_by_eb(SHARPSL_FTL_PART_SIZE, mtd);
+
+	/* FTL reserves 5% of the blocks + 1 spare  */
+	ftl->logmax = ((phymax * 95) / 100) - 1;
+
+	ftl->log2phy = kmalloc_array(ftl->logmax, sizeof(*ftl->log2phy),
+				     GFP_KERNEL);
+	if (!ftl->log2phy) {
+		ret = -ENOMEM;
+		goto exit;
+	}
+
+	/* initialize ftl->log2phy */
+	for (i = 0; i < ftl->logmax; i++)
+		ftl->log2phy[i] = UINT_MAX;
+
+	/* create physical-logical table */
+	for (block_num = 0; block_num < phymax; block_num++) {
+		block_adr = block_num * mtd->erasesize;
+
+		if (mtd_block_isbad(mtd, block_adr))
+			continue;
+
+		if (sharpsl_nand_read_oob(mtd, block_adr, oob))
+			continue;
+
+		/* get logical block */
+		log_num = sharpsl_nand_get_logical_num(oob);
+
+		/* cut-off errors and skip the out-of-range values */
+		if (log_num > 0 && log_num < ftl->logmax) {
+			if (ftl->log2phy[log_num] == UINT_MAX)
+				ftl->log2phy[log_num] = block_num;
+		}
+	}
+
+	pr_info("Sharp SL FTL: %d blocks used (%d logical, %d reserved)\n",
+		phymax, ftl->logmax, phymax - ftl->logmax);
+
+	ret = 0;
+exit:
+	kfree(oob);
+	return ret;
+}
+
+void sharpsl_nand_cleanup_ftl(struct sharpsl_ftl *ftl)
+{
+	kfree(ftl->log2phy);
+}
+
+static int sharpsl_nand_read_laddr(struct mtd_info *mtd,
+				   loff_t from,
+				   size_t len,
+				   void *buf,
+				   struct sharpsl_ftl *ftl)
+{
+	unsigned int log_num, final_log_num;
+	unsigned int block_num;
+	loff_t block_adr;
+	loff_t block_ofs;
+	size_t retlen;
+	int err;
+
+	log_num = mtd_div_by_eb((u32)from, mtd);
+	final_log_num = mtd_div_by_eb(((u32)from + len - 1), mtd);
+
+	if (len <= 0 || log_num >= ftl->logmax || final_log_num > log_num)
+		return -EINVAL;
+
+	block_num = ftl->log2phy[log_num];
+	block_adr = block_num * mtd->erasesize;
+	block_ofs = mtd_mod_by_eb((u32)from, mtd);
+
+	err = mtd_read(mtd, block_adr + block_ofs, len, &retlen, buf);
+	/* Ignore corrected ECC errors */
+	if (mtd_is_bitflip(err))
+		err = 0;
+
+	if (!err && retlen != len)
+		err = -EIO;
+
+	if (err)
+		pr_err("sharpslpart: error, read failed at %#llx\n",
+		       block_adr + block_ofs);
+
+	return err;
+}
+
+/*
+ * MTD Partition Parser
+ *
+ * Sample values read from SL-C860
+ *
+ * # cat /proc/mtd
+ * dev:    size   erasesize  name
+ * mtd0: 006d0000 00020000 "Filesystem"
+ * mtd1: 00700000 00004000 "smf"
+ * mtd2: 03500000 00004000 "root"
+ * mtd3: 04400000 00004000 "home"
+ *
+ * PARTITIONINFO1
+ * 0x00060000: 00 00 00 00 00 00 70 00 42 4f 4f 54 00 00 00 00  ......p.BOOT....
+ * 0x00060010: 00 00 70 00 00 00 c0 03 46 53 52 4f 00 00 00 00  ..p.....FSRO....
+ * 0x00060020: 00 00 c0 03 00 00 00 04 46 53 52 57 00 00 00 00  ........FSRW....
+ */
+struct sharpsl_nand_partinfo {
+	__le32 start;
+	__le32 end;
+	__be32 magic;
+	u32 reserved;
+};
+
+static int sharpsl_nand_read_partinfo(struct mtd_info *master,
+				      loff_t from,
+				      size_t len,
+				      struct sharpsl_nand_partinfo *buf,
+				      struct sharpsl_ftl *ftl)
+{
+	int ret;
+
+	ret = sharpsl_nand_read_laddr(master, from, len, buf, ftl);
+	if (ret)
+		return ret;
+
+	/* check for magics */
+	if (be32_to_cpu(buf[0].magic) != BOOT_MAGIC ||
+	    be32_to_cpu(buf[1].magic) != FSRO_MAGIC ||
+	    be32_to_cpu(buf[2].magic) != FSRW_MAGIC) {
+		pr_err("sharpslpart: magic values mismatch\n");
+		return -EINVAL;
+	}
+
+	/* fixup for hardcoded value 64 MiB (for older models) */
+	buf[2].end = cpu_to_le32(master->size);
+
+	/* extra sanity check */
+	if (le32_to_cpu(buf[0].end) <= le32_to_cpu(buf[0].start) ||
+	    le32_to_cpu(buf[1].start) < le32_to_cpu(buf[0].end) ||
+	    le32_to_cpu(buf[1].end) <= le32_to_cpu(buf[1].start) ||
+	    le32_to_cpu(buf[2].start) < le32_to_cpu(buf[1].end) ||
+	    le32_to_cpu(buf[2].end) <= le32_to_cpu(buf[2].start)) {
+		pr_err("sharpslpart: partition sizes mismatch\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int sharpsl_parse_mtd_partitions(struct mtd_info *master,
+					const struct mtd_partition **pparts,
+					struct mtd_part_parser_data *data)
+{
+	struct sharpsl_ftl ftl;
+	struct sharpsl_nand_partinfo buf[SHARPSL_NAND_PARTS];
+	struct mtd_partition *sharpsl_nand_parts;
+	int err;
+
+	/* check that OOB bytes 8 to 15 used by the FTL are actually free */
+	err = sharpsl_nand_check_ooblayout(master);
+	if (err)
+		return err;
+
+	/* init logical mgmt (FTL) */
+	err = sharpsl_nand_init_ftl(master, &ftl);
+	if (err)
+		return err;
+
+	/* read and validate first partition table */
+	pr_info("sharpslpart: try reading first partition table\n");
+	err = sharpsl_nand_read_partinfo(master,
+					 SHARPSL_PARTINFO1_LADDR,
+					 sizeof(buf), buf, &ftl);
+	if (err) {
+		/* fallback: read second partition table */
+		pr_warn("sharpslpart: first partition table is invalid, retry using the second\n");
+		err = sharpsl_nand_read_partinfo(master,
+						 SHARPSL_PARTINFO2_LADDR,
+						 sizeof(buf), buf, &ftl);
+	}
+
+	/* cleanup logical mgmt (FTL) */
+	sharpsl_nand_cleanup_ftl(&ftl);
+
+	if (err) {
+		pr_err("sharpslpart: both partition tables are invalid\n");
+		return err;
+	}
+
+	sharpsl_nand_parts = kzalloc(sizeof(*sharpsl_nand_parts) *
+				     SHARPSL_NAND_PARTS, GFP_KERNEL);
+	if (!sharpsl_nand_parts)
+		return -ENOMEM;
+
+	/* original names */
+	sharpsl_nand_parts[0].name = "smf";
+	sharpsl_nand_parts[0].offset = le32_to_cpu(buf[0].start);
+	sharpsl_nand_parts[0].size = le32_to_cpu(buf[0].end) -
+				     le32_to_cpu(buf[0].start);
+
+	sharpsl_nand_parts[1].name = "root";
+	sharpsl_nand_parts[1].offset = le32_to_cpu(buf[1].start);
+	sharpsl_nand_parts[1].size = le32_to_cpu(buf[1].end) -
+				     le32_to_cpu(buf[1].start);
+
+	sharpsl_nand_parts[2].name = "home";
+	sharpsl_nand_parts[2].offset = le32_to_cpu(buf[2].start);
+	sharpsl_nand_parts[2].size = le32_to_cpu(buf[2].end) -
+				     le32_to_cpu(buf[2].start);
+
+	*pparts = sharpsl_nand_parts;
+	return SHARPSL_NAND_PARTS;
+}
+
+static struct mtd_part_parser sharpsl_mtd_parser = {
+	.parse_fn = sharpsl_parse_mtd_partitions,
+	.name = "sharpslpart",
+};
+module_mtd_part_parser(sharpsl_mtd_parser);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Andrea Adami <andrea.adami@gmail.com>");
+MODULE_DESCRIPTION("MTD partitioning for NAND flash on Sharp SL Series");