// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * BCM947xx nvram variable access
 *
 * Copyright (C) 2005 Broadcom Corporation
 * Copyright (C) 2006 Felix Fietkau <nbd@openwrt.org>
 * Copyright (C) 2010-2012 Hauke Mehrtens <hauke@hauke-m.de>
 */

#include <linux/io.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/mtd/mtd.h>
#include <linux/bcm47xx_nvram.h>

#define NVRAM_MAGIC                     0x48534C46      /* 'FLSH' */
#define NVRAM_SPACE                     0x10000
#define NVRAM_MAX_GPIO_ENTRIES          32
#define NVRAM_MAX_GPIO_VALUE_LEN        30

#define FLASH_MIN               0x00020000      /* Minimum flash size */

struct nvram_header {
        u32 magic;
        u32 len;
        u32 crc_ver_init;       /* 0:7 crc, 8:15 ver, 16:31 sdram_init */
        u32 config_refresh;     /* 0:15 sdram_config, 16:31 sdram_refresh */
        u32 config_ncdl;        /* ncdl values for memc */
};

static char nvram_buf[NVRAM_SPACE];
static size_t nvram_len;
static const u32 nvram_sizes[] = {0x6000, 0x8000, 0xF000, 0x10000};

static u32 find_nvram_size(void __iomem *end)
{
        struct nvram_header __iomem *header;
        int i;

        for (i = 0; i < ARRAY_SIZE(nvram_sizes); i++) {
                header = (struct nvram_header *)(end - nvram_sizes[i]);
                if (header->magic == NVRAM_MAGIC)
                        return nvram_sizes[i];
        }

        return 0;
}

/* Probe for NVRAM header */
static int nvram_find_and_copy(void __iomem *iobase, u32 lim)
{
        struct nvram_header __iomem *header;
        u32 off;
        u32 size;

        if (nvram_len) {
                pr_warn("nvram already initialized\n");
                return -EEXIST;
        }

        /* TODO: when nvram is on nand flash check for bad blocks first. */
        off = FLASH_MIN;
        while (off <= lim) {
                /* Windowed flash access */
                size = find_nvram_size(iobase + off);
                if (size) {
                        header = (struct nvram_header *)(iobase + off - size);
                        goto found;
                }
                off <<= 1;
        }

        /* Try embedded NVRAM at 4 KB and 1 KB as last resorts */
        header = (struct nvram_header *)(iobase + 4096);
        if (header->magic == NVRAM_MAGIC) {
                size = NVRAM_SPACE;
                goto found;
        }

        header = (struct nvram_header *)(iobase + 1024);
        if (header->magic == NVRAM_MAGIC) {
                size = NVRAM_SPACE;
                goto found;
        }

        pr_err("no nvram found\n");
        return -ENXIO;

found:
        __ioread32_copy(nvram_buf, header, sizeof(*header) / 4);
        nvram_len = ((struct nvram_header *)(nvram_buf))->len;
        if (nvram_len > size) {
                pr_err("The nvram size according to the header seems to be bigger than the partition on flash\n");
                nvram_len = size;
        }
        if (nvram_len >= NVRAM_SPACE) {
                pr_err("nvram on flash (%i bytes) is bigger than the reserved space in memory, will just copy the first %i bytes\n",
                       nvram_len, NVRAM_SPACE - 1);
                nvram_len = NVRAM_SPACE - 1;
        }
        /* proceed reading data after header */
        __ioread32_copy(nvram_buf + sizeof(*header), header + 1,
                        DIV_ROUND_UP(nvram_len, 4));
        nvram_buf[NVRAM_SPACE - 1] = '\0';

        return 0;
}

/*
 * On bcm47xx we need access to the NVRAM very early, so we can't use mtd
 * subsystem to access flash. We can't even use platform device / driver to
 * store memory offset.
 * To handle this we provide following symbol. It's supposed to be called as
 * soon as we get info about flash device, before any NVRAM entry is needed.
 */
int bcm47xx_nvram_init_from_mem(u32 base, u32 lim)
{
        void __iomem *iobase;
        int err;

        iobase = ioremap_nocache(base, lim);
        if (!iobase)
                return -ENOMEM;

        err = nvram_find_and_copy(iobase, lim);

        iounmap(iobase);

        return err;
}

static int nvram_init(void)
{
#ifdef CONFIG_MTD
        struct mtd_info *mtd;
        struct nvram_header header;
        size_t bytes_read;
        int err;

        mtd = get_mtd_device_nm("nvram");
        if (IS_ERR(mtd))
                return -ENODEV;

        err = mtd_read(mtd, 0, sizeof(header), &bytes_read, (uint8_t *)&header);
        if (!err && header.magic == NVRAM_MAGIC &&
            header.len > sizeof(header)) {
                nvram_len = header.len;
                if (nvram_len >= NVRAM_SPACE) {
                        pr_err("nvram on flash (%i bytes) is bigger than the reserved space in memory, will just copy the first %i bytes\n",
                                header.len, NVRAM_SPACE);
                        nvram_len = NVRAM_SPACE - 1;
                }

                err = mtd_read(mtd, 0, nvram_len, &nvram_len,
                               (u8 *)nvram_buf);
                return err;
        }
#endif

        return -ENXIO;
}

int bcm47xx_nvram_getenv(const char *name, char *val, size_t val_len)
{
        char *var, *value, *end, *eq;
        int err;

        if (!name)
                return -EINVAL;

        if (!nvram_len) {
                err = nvram_init();
                if (err)
                        return err;
        }

        /* Look for name=value and return value */
        var = &nvram_buf[sizeof(struct nvram_header)];
        end = nvram_buf + sizeof(nvram_buf);
        while (var < end && *var) {
                eq = strchr(var, '=');
                if (!eq)
                        break;
                value = eq + 1;
                if (eq - var == strlen(name) &&
                    strncmp(var, name, eq - var) == 0)
                        return snprintf(val, val_len, "%s", value);
                var = value + strlen(value) + 1;
        }
        return -ENOENT;
}
EXPORT_SYMBOL(bcm47xx_nvram_getenv);

int bcm47xx_nvram_gpio_pin(const char *name)
{
        int i, err;
        char nvram_var[] = "gpioXX";
        char buf[NVRAM_MAX_GPIO_VALUE_LEN];

        /* TODO: Optimize it to don't call getenv so many times */
        for (i = 0; i < NVRAM_MAX_GPIO_ENTRIES; i++) {
                err = snprintf(nvram_var, sizeof(nvram_var), "gpio%i", i);
                if (err <= 0)
                        continue;
                err = bcm47xx_nvram_getenv(nvram_var, buf, sizeof(buf));
                if (err <= 0)
                        continue;
                if (!strcmp(name, buf))
                        return i;
        }
        return -ENOENT;
}
EXPORT_SYMBOL(bcm47xx_nvram_gpio_pin);

char *bcm47xx_nvram_get_contents(size_t *nvram_size)
{
        int err;
        char *nvram;

        if (!nvram_len) {
                err = nvram_init();
                if (err)
                        return NULL;
        }

        *nvram_size = nvram_len - sizeof(struct nvram_header);
        nvram = vmalloc(*nvram_size);
        if (!nvram)
                return NULL;
        memcpy(nvram, &nvram_buf[sizeof(struct nvram_header)], *nvram_size);

        return nvram;
}
EXPORT_SYMBOL(bcm47xx_nvram_get_contents);

MODULE_LICENSE("GPL v2");