mtd: parsers: add support for Sercomm partitions

This adds an MTD partition parser for the Sercomm partition table that
is used in some Beeline, Netgear and Sercomm routers.

The Sercomm partition map table contains real partition offsets, which
may differ from device to device depending on the number and location of
bad blocks on NAND.

Original patch (proposed by NOGUCHI Hiroshi):
Link: https://github.com/openwrt/openwrt/pull/1318#issuecomment-420607394

Signed-off-by: NOGUCHI Hiroshi <[e-mail]>
Signed-off-by: Mikhail Zhilkin <[e-mail]>
Signed-off-by: Miquel Raynal <[e-mail]>
Link: https://lore.kernel.org/linux-mtd/[e-mail]

drivers/mtd/parsers/Kconfig

···
 	help
 	  This provides support for parsing partitions from Shared Memory (SMEM)
 	  for NAND and SPI flash on Qualcomm platforms.
+
+config MTD_SERCOMM_PARTS
+	tristate "Sercomm partition table parser"
+	depends on MTD && RALINK
+	help
+	  This provides partitions table parser for devices with Sercomm
+	  partition map. This partition table contains real partition
+	  offsets, which may differ from device to device depending on the
+	  number and location of bad blocks on NAND.

drivers/mtd/parsers/Makefile

···
 obj-$(CONFIG_MTD_PARSER_IMAGETAG)	+= parser_imagetag.o
 obj-$(CONFIG_MTD_AFS_PARTS)		+= afs.o
 obj-$(CONFIG_MTD_PARSER_TRX)		+= parser_trx.o
+obj-$(CONFIG_MTD_SERCOMM_PARTS)		+= scpart.o
 obj-$(CONFIG_MTD_SHARPSL_PARTS)		+= sharpslpart.o
 obj-$(CONFIG_MTD_REDBOOT_PARTS)		+= redboot.o
 obj-$(CONFIG_MTD_QCOMSMEM_PARTS)	+= qcomsmempart.o

drivers/mtd/parsers/scpart.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *    drivers/mtd/scpart.c: Sercomm Partition Parser
+ *
+ *    Copyright (C) 2018 NOGUCHI Hiroshi
+ *    Copyright (C) 2022 Mikhail Zhilkin
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+#include <linux/module.h>
+
+#define	MOD_NAME	"scpart"
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#define pr_fmt(fmt) MOD_NAME ": " fmt
+
+#define	ID_ALREADY_FOUND	0xffffffffUL
+
+#define	MAP_OFFS_IN_BLK		0x800
+#define	MAP_MIRROR_NUM		2
+
+static const char sc_part_magic[] = {
+	'S', 'C', 'F', 'L', 'M', 'A', 'P', 'O', 'K', '\0',
+};
+#define	PART_MAGIC_LEN		sizeof(sc_part_magic)
+
+/* assumes that all fields are set by CPU native endian */
+struct sc_part_desc {
+	uint32_t	part_id;
+	uint32_t	part_offs;
+	uint32_t	part_bytes;
+};
+
+static uint32_t scpart_desc_is_valid(struct sc_part_desc *pdesc)
+{
+	return ((pdesc->part_id != 0xffffffffUL) &&
+		(pdesc->part_offs != 0xffffffffUL) &&
+		(pdesc->part_bytes != 0xffffffffUL));
+}
+
+static int scpart_scan_partmap(struct mtd_info *master, loff_t partmap_offs,
+			       struct sc_part_desc **ppdesc)
+{
+	int cnt = 0;
+	int res = 0;
+	int res2;
+	loff_t offs;
+	size_t retlen;
+	struct sc_part_desc *pdesc = NULL;
+	struct sc_part_desc *tmpdesc;
+	uint8_t *buf;
+
+	buf = kzalloc(master->erasesize, GFP_KERNEL);
+	if (!buf) {
+		res = -ENOMEM;
+		goto out;
+	}
+
+	res2 = mtd_read(master, partmap_offs, master->erasesize, &retlen, buf);
+	if (res2 || retlen != master->erasesize) {
+		res = -EIO;
+		goto free;
+	}
+
+	for (offs = MAP_OFFS_IN_BLK;
+	     offs < master->erasesize - sizeof(*tmpdesc);
+	     offs += sizeof(*tmpdesc)) {
+		tmpdesc = (struct sc_part_desc *)&buf[offs];
+		if (!scpart_desc_is_valid(tmpdesc))
+			break;
+		cnt++;
+	}
+
+	if (cnt > 0) {
+		int bytes = cnt * sizeof(*pdesc);
+
+		pdesc = kcalloc(cnt, sizeof(*pdesc), GFP_KERNEL);
+		if (!pdesc) {
+			res = -ENOMEM;
+			goto free;
+		}
+		memcpy(pdesc, &(buf[MAP_OFFS_IN_BLK]), bytes);
+
+		*ppdesc = pdesc;
+		res = cnt;
+	}
+
+free:
+	kfree(buf);
+
+out:
+	return res;
+}
+
+static int scpart_find_partmap(struct mtd_info *master,
+			       struct sc_part_desc **ppdesc)
+{
+	int magic_found = 0;
+	int res = 0;
+	int res2;
+	loff_t offs = 0;
+	size_t retlen;
+	uint8_t rdbuf[PART_MAGIC_LEN];
+
+	while ((magic_found < MAP_MIRROR_NUM) &&
+			(offs < master->size) &&
+			 !mtd_block_isbad(master, offs)) {
+		res2 = mtd_read(master, offs, PART_MAGIC_LEN, &retlen, rdbuf);
+		if (res2 || retlen != PART_MAGIC_LEN) {
+			res = -EIO;
+			goto out;
+		}
+		if (!memcmp(rdbuf, sc_part_magic, PART_MAGIC_LEN)) {
+			pr_debug("Signature found at 0x%llx\n", offs);
+			magic_found++;
+			res = scpart_scan_partmap(master, offs, ppdesc);
+			if (res > 0)
+				goto out;
+		}
+		offs += master->erasesize;
+	}
+
+out:
+	if (res > 0)
+		pr_info("Valid 'SC PART MAP' (%d partitions) found at 0x%llx\n", res, offs);
+	else
+		pr_info("No valid 'SC PART MAP' was found\n");
+
+	return res;
+}
+
+static int scpart_parse(struct mtd_info *master,
+			const struct mtd_partition **pparts,
+			struct mtd_part_parser_data *data)
+{
+	const char *partname;
+	int n;
+	int nr_scparts;
+	int nr_parts = 0;
+	int res = 0;
+	struct sc_part_desc *scpart_map = NULL;
+	struct mtd_partition *parts = NULL;
+	struct device_node *mtd_node;
+	struct device_node *ofpart_node;
+	struct device_node *pp;
+
+	mtd_node = mtd_get_of_node(master);
+	if (!mtd_node) {
+		res = -ENOENT;
+		goto out;
+	}
+
+	ofpart_node = of_get_child_by_name(mtd_node, "partitions");
+	if (!ofpart_node) {
+		pr_info("%s: 'partitions' subnode not found on %pOF.\n",
+				master->name, mtd_node);
+		res = -ENOENT;
+		goto out;
+	}
+
+	nr_scparts = scpart_find_partmap(master, &scpart_map);
+	if (nr_scparts <= 0) {
+		pr_info("No any partitions was found in 'SC PART MAP'.\n");
+		res = -ENOENT;
+		goto free;
+	}
+
+	parts = kcalloc(of_get_child_count(ofpart_node), sizeof(*parts),
+		GFP_KERNEL);
+	if (!parts) {
+		res = -ENOMEM;
+		goto free;
+	}
+
+	for_each_child_of_node(ofpart_node, pp) {
+		u32 scpart_id;
+
+		if (of_property_read_u32(pp, "sercomm,scpart-id", &scpart_id))
+			continue;
+
+		for (n = 0 ; n < nr_scparts ; n++)
+			if ((scpart_map[n].part_id != ID_ALREADY_FOUND) &&
+					(scpart_id == scpart_map[n].part_id))
+				break;
+		if (n >= nr_scparts)
+			/* not match */
+			continue;
+
+		/* add the partition found in OF into MTD partition array */
+		parts[nr_parts].offset = scpart_map[n].part_offs;
+		parts[nr_parts].size = scpart_map[n].part_bytes;
+		parts[nr_parts].of_node = pp;
+
+		if (!of_property_read_string(pp, "label", &partname))
+			parts[nr_parts].name = partname;
+		if (of_property_read_bool(pp, "read-only"))
+			parts[nr_parts].mask_flags |= MTD_WRITEABLE;
+		if (of_property_read_bool(pp, "lock"))
+			parts[nr_parts].mask_flags |= MTD_POWERUP_LOCK;
+
+		/* mark as 'done' */
+		scpart_map[n].part_id = ID_ALREADY_FOUND;
+
+		nr_parts++;
+	}
+
+	if (nr_parts > 0) {
+		*pparts = parts;
+		res = nr_parts;
+	} else
+		pr_info("No partition in OF matches partition ID with 'SC PART MAP'.\n");
+
+	of_node_put(pp);
+
+free:
+	kfree(scpart_map);
+	if (res <= 0)
+		kfree(parts);
+
+out:
+	return res;
+}
+
+static const struct of_device_id scpart_parser_of_match_table[] = {
+	{ .compatible = "sercomm,sc-partitions" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, scpart_parser_of_match_table);
+
+static struct mtd_part_parser scpart_parser = {
+	.parse_fn = scpart_parse,
+	.name = "scpart",
+	.of_match_table = scpart_parser_of_match_table,
+};
+module_mtd_part_parser(scpart_parser);
+
+/* mtd parsers will request the module by parser name */
+MODULE_ALIAS("scpart");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("NOGUCHI Hiroshi <[e-mail]>");
+MODULE_AUTHOR("Mikhail Zhilkin <[e-mail]>");
+MODULE_DESCRIPTION("Sercomm partition parser");