nvram.c

/*
 * 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>
 *
 * 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.
 */

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

#define NVRAM_MAGIC		0x48534C46	/* 'FLSH' */
#define NVRAM_SPACE		0x8000

#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 const u32 nvram_sizes[] = {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;
	int i;
	u32 off;
	u32 *src, *dst;
	u32 size;

	if (nvram_buf[0]) {
		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:
	if (header->len > size)
		pr_err("The nvram size accoridng to the header seems to be bigger than the partition on flash\n");
	if (header->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);

	src = (u32 *) header;
	dst = (u32 *) nvram_buf;
	for (i = 0; i < sizeof(struct nvram_header); i += 4)
		*dst++ = __raw_readl(src++);
	for (; i < header->len && i < NVRAM_SPACE && i < size; i += 4)
		*dst++ = readl(src++);

	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, i;

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

	for (i = 0; i < ARRAY_SIZE(nvram_sizes); i++) {
		loff_t from = mtd->size - nvram_sizes[i];

		if (from < 0)
			continue;

		err = mtd_read(mtd, from, sizeof(header), &bytes_read,
			       (uint8_t *)&header);
		if (!err && header.magic == NVRAM_MAGIC) {
			u8 *dst = (uint8_t *)nvram_buf;
			size_t len = header.len;

			if (header.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);
				len = NVRAM_SPACE;
			}

			err = mtd_read(mtd, from, len, &bytes_read, dst);
			if (err)
				return err;

			return 0;
		}
	}
#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_buf[0]) {
		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) - 2;
	end[0] = end[1] = '\0';
	for (; *var; var = value + strlen(value) + 1) {
		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);
		}
	}
	return -ENOENT;
}
EXPORT_SYMBOL(bcm47xx_nvram_getenv);

int bcm47xx_nvram_gpio_pin(const char *name)
{
	int i, err;
	char nvram_var[10];
	char buf[30];

	for (i = 0; i < 32; 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);