// SPDX-License-Identifier: GPL-2.0-only
/*
 * BCM47XX MTD partitioning
 *
 * Copyright © 2012 Rafał Miłecki <zajec5@gmail.com>
 */

#include <linux/bcm47xx_nvram.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>

#include <uapi/linux/magic.h>

/*
 * NAND flash on Netgear R6250 was verified to contain 15 partitions.
 * This will result in allocating too big array for some old devices, but the
 * memory will be freed soon anyway (see mtd_device_parse_register).
 */
#define BCM47XXPART_MAX_PARTS           20

/*
 * Amount of bytes we read when analyzing each block of flash memory.
 * Set it big enough to allow detecting partition and reading important data.
 */
#define BCM47XXPART_BYTES_TO_READ       0x4e8

/* Magics */
#define BOARD_DATA_MAGIC                0x5246504D      /* MPFR */
#define BOARD_DATA_MAGIC2               0xBD0D0BBD
#define CFE_MAGIC                       0x43464531      /* 1EFC */
#define FACTORY_MAGIC                   0x59544346      /* FCTY */
#define NVRAM_HEADER                    0x48534C46      /* FLSH */
#define POT_MAGIC1                      0x54544f50      /* POTT */
#define POT_MAGIC2                      0x504f          /* OP */
#define ML_MAGIC1                       0x39685a42
#define ML_MAGIC2                       0x26594131
#define TRX_MAGIC                       0x30524448
#define SHSQ_MAGIC                      0x71736873      /* shsq (weird ZTE H218N endianness) */

static const char * const trx_types[] = { "trx", NULL };

struct trx_header {
        uint32_t magic;
        uint32_t length;
        uint32_t crc32;
        uint16_t flags;
        uint16_t version;
        uint32_t offset[3];
} __packed;

static void bcm47xxpart_add_part(struct mtd_partition *part, const char *name,
                                 u64 offset, uint32_t mask_flags)
{
        part->name = name;
        part->offset = offset;
        part->mask_flags = mask_flags;
}

/**
 * bcm47xxpart_bootpartition - gets index of TRX partition used by bootloader
 *
 * Some devices may have more than one TRX partition. In such case one of them
 * is the main one and another a failsafe one. Bootloader may fallback to the
 * failsafe firmware if it detects corruption of the main image.
 *
 * This function provides info about currently used TRX partition. It's the one
 * containing kernel started by the bootloader.
 */
static int bcm47xxpart_bootpartition(void)
{
        char buf[4];
        int bootpartition;

        /* Check CFE environment variable */
        if (bcm47xx_nvram_getenv("bootpartition", buf, sizeof(buf)) > 0) {
                if (!kstrtoint(buf, 0, &bootpartition))
                        return bootpartition;
        }

        return 0;
}

static int bcm47xxpart_parse(struct mtd_info *master,
                             const struct mtd_partition **pparts,
                             struct mtd_part_parser_data *data)
{
        struct mtd_partition *parts;
        uint8_t i, curr_part = 0;
        uint32_t *buf;
        size_t bytes_read;
        uint32_t offset;
        uint32_t blocksize = master->erasesize;
        int trx_parts[2]; /* Array with indexes of TRX partitions */
        int trx_num = 0; /* Number of found TRX partitions */
        static const int possible_nvram_sizes[] = { 0x8000, 0xF000, 0x10000, };
        int err;

        /*
         * Some really old flashes (like AT45DB*) had smaller erasesize-s, but
         * partitions were aligned to at least 0x1000 anyway.
         */
        if (blocksize < 0x1000)
                blocksize = 0x1000;

        /* Alloc */
        parts = kzalloc_objs(struct mtd_partition, BCM47XXPART_MAX_PARTS);
        if (!parts)
                return -ENOMEM;

        buf = kzalloc(BCM47XXPART_BYTES_TO_READ, GFP_KERNEL);
        if (!buf) {
                kfree(parts);
                return -ENOMEM;
        }

        /* Parse block by block looking for magics */
        for (offset = 0; offset <= master->size - blocksize;
             offset += blocksize) {
                /* Nothing more in higher memory on BCM47XX (MIPS) */
                if (IS_ENABLED(CONFIG_BCM47XX) && offset >= 0x2000000)
                        break;

                if (curr_part >= BCM47XXPART_MAX_PARTS) {
                        pr_warn("Reached maximum number of partitions, scanning stopped!\n");
                        break;
                }

                /* Read beginning of the block */
                err = mtd_read(master, offset, BCM47XXPART_BYTES_TO_READ,
                               &bytes_read, (uint8_t *)buf);
                if (err && !mtd_is_bitflip(err)) {
                        pr_err("mtd_read error while parsing (offset: 0x%X): %d\n",
                               offset, err);
                        continue;
                }

                /* Magic or small NVRAM at 0x400 */
                if ((buf[0x4e0 / 4] == CFE_MAGIC && buf[0x4e4 / 4] == CFE_MAGIC) ||
                    (buf[0x400 / 4] == NVRAM_HEADER)) {
                        bcm47xxpart_add_part(&parts[curr_part++], "boot",
                                             offset, MTD_WRITEABLE);
                        continue;
                }

                /*
                 * board_data starts with board_id which differs across boards,
                 * but we can use 'MPFR' (hopefully) magic at 0x100
                 */
                if (buf[0x100 / 4] == BOARD_DATA_MAGIC) {
                        bcm47xxpart_add_part(&parts[curr_part++], "board_data",
                                             offset, MTD_WRITEABLE);
                        continue;
                }

                /* Found on Huawei E970 */
                if (buf[0x000 / 4] == FACTORY_MAGIC) {
                        bcm47xxpart_add_part(&parts[curr_part++], "factory",
                                             offset, MTD_WRITEABLE);
                        continue;
                }

                /* POT(TOP) */
                if (buf[0x000 / 4] == POT_MAGIC1 &&
                    (buf[0x004 / 4] & 0xFFFF) == POT_MAGIC2) {
                        bcm47xxpart_add_part(&parts[curr_part++], "POT", offset,
                                             MTD_WRITEABLE);
                        continue;
                }

                /* ML */
                if (buf[0x010 / 4] == ML_MAGIC1 &&
                    buf[0x014 / 4] == ML_MAGIC2) {
                        bcm47xxpart_add_part(&parts[curr_part++], "ML", offset,
                                             MTD_WRITEABLE);
                        continue;
                }

                /* TRX */
                if (buf[0x000 / 4] == TRX_MAGIC) {
                        struct trx_header *trx;
                        uint32_t last_subpart;
                        uint32_t trx_size;

                        if (trx_num >= ARRAY_SIZE(trx_parts))
                                pr_warn("No enough space to store another TRX found at 0x%X\n",
                                        offset);
                        else
                                trx_parts[trx_num++] = curr_part;
                        bcm47xxpart_add_part(&parts[curr_part++], "firmware",
                                             offset, 0);

                        /*
                         * Try to find TRX size. The "length" field isn't fully
                         * reliable as it could be decreased to make CRC32 cover
                         * only part of TRX data. It's commonly used as checksum
                         * can't cover e.g. ever-changing rootfs partition.
                         * Use offsets as helpers for assuming min TRX size.
                         */
                        trx = (struct trx_header *)buf;
                        last_subpart = max3(trx->offset[0], trx->offset[1],
                                            trx->offset[2]);
                        trx_size = max(trx->length, last_subpart + blocksize);

                        /*
                         * Skip the TRX data. Decrease offset by block size as
                         * the next loop iteration will increase it.
                         */
                        offset += roundup(trx_size, blocksize) - blocksize;
                        continue;
                }

                /* Squashfs on devices not using TRX */
                if (le32_to_cpu(buf[0x000 / 4]) == SQUASHFS_MAGIC ||
                    buf[0x000 / 4] == SHSQ_MAGIC) {
                        bcm47xxpart_add_part(&parts[curr_part++], "rootfs",
                                             offset, 0);
                        continue;
                }

                /*
                 * New (ARM?) devices may have NVRAM in some middle block. Last
                 * block will be checked later, so skip it.
                 */
                if (offset != master->size - blocksize &&
                    buf[0x000 / 4] == NVRAM_HEADER) {
                        bcm47xxpart_add_part(&parts[curr_part++], "nvram",
                                             offset, 0);
                        continue;
                }

                /* Read middle of the block */
                err = mtd_read(master, offset + (blocksize / 2), 0x4, &bytes_read,
                               (uint8_t *)buf);
                if (err && !mtd_is_bitflip(err)) {
                        pr_err("mtd_read error while parsing (offset: 0x%X): %d\n",
                               offset + (blocksize / 2), err);
                        continue;
                }

                /* Some devices (ex. WNDR3700v3) don't have a standard 'MPFR' */
                if (buf[0x000 / 4] == BOARD_DATA_MAGIC2) {
                        bcm47xxpart_add_part(&parts[curr_part++], "board_data",
                                             offset, MTD_WRITEABLE);
                        continue;
                }
        }

        /* Look for NVRAM at the end of the last block. */
        for (i = 0; i < ARRAY_SIZE(possible_nvram_sizes); i++) {
                if (curr_part >= BCM47XXPART_MAX_PARTS) {
                        pr_warn("Reached maximum number of partitions, scanning stopped!\n");
                        break;
                }

                offset = master->size - possible_nvram_sizes[i];
                err = mtd_read(master, offset, 0x4, &bytes_read,
                               (uint8_t *)buf);
                if (err && !mtd_is_bitflip(err)) {
                        pr_err("mtd_read error while reading (offset 0x%X): %d\n",
                               offset, err);
                        continue;
                }

                /* Standard NVRAM */
                if (buf[0] == NVRAM_HEADER) {
                        bcm47xxpart_add_part(&parts[curr_part++], "nvram",
                                             master->size - blocksize, 0);
                        break;
                }
        }

        kfree(buf);

        /*
         * Assume that partitions end at the beginning of the one they are
         * followed by.
         */
        for (i = 0; i < curr_part; i++) {
                u64 next_part_offset = (i < curr_part - 1) ?
                                       parts[i + 1].offset : master->size;

                parts[i].size = next_part_offset - parts[i].offset;
        }

        /* If there was TRX parse it now */
        for (i = 0; i < trx_num; i++) {
                struct mtd_partition *trx = &parts[trx_parts[i]];

                if (i == bcm47xxpart_bootpartition())
                        trx->types = trx_types;
                else
                        trx->name = "failsafe";
        }

        *pparts = parts;
        return curr_part;
};

static const struct of_device_id bcm47xxpart_of_match_table[] = {
        { .compatible = "brcm,bcm947xx-cfe-partitions" },
        {},
};
MODULE_DEVICE_TABLE(of, bcm47xxpart_of_match_table);

static struct mtd_part_parser bcm47xxpart_mtd_parser = {
        .parse_fn = bcm47xxpart_parse,
        .name = "bcm47xxpart",
        .of_match_table = bcm47xxpart_of_match_table,
};
module_mtd_part_parser(bcm47xxpart_mtd_parser);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("MTD partitioning for BCM47XX flash memories");