// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) ????		Jochen Schäuble <psionic@psionic.de>
 * Copyright (c) 2003-2004	Joern Engel <joern@wh.fh-wedel.de>
 *
 * Usage:
 *
 * one commend line parameter per device, each in the form:
 *   phram=<name>,<start>,<len>[,<erasesize>]
 * <name> may be up to 63 characters.
 * <start>, <len>, and <erasesize> can be octal, decimal or hexadecimal.  If followed
 * by "ki", "Mi" or "Gi", the numbers will be interpreted as kilo, mega or
 * gigabytes. <erasesize> is optional and defaults to PAGE_SIZE.
 *
 * Example:
 *	phram=swap,64Mi,128Mi phram=test,900Mi,1Mi,64Ki
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/io.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>
#include <asm/div64.h>
#include <linux/platform_device.h>
#include <linux/of_address.h>
#include <linux/of.h>

struct phram_mtd_list {
	struct mtd_info mtd;
	struct list_head list;
	bool cached;
};

static LIST_HEAD(phram_list);

static int phram_erase(struct mtd_info *mtd, struct erase_info *instr)
{
	u_char *start = mtd->priv;

	memset(start + instr->addr, 0xff, instr->len);

	return 0;
}

static int phram_point(struct mtd_info *mtd, loff_t from, size_t len,
		size_t *retlen, void **virt, resource_size_t *phys)
{
	*virt = mtd->priv + from;
	*retlen = len;
	return 0;
}

static int phram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
{
	return 0;
}

static int phram_read(struct mtd_info *mtd, loff_t from, size_t len,
		size_t *retlen, u_char *buf)
{
	u_char *start = mtd->priv;

	memcpy(buf, start + from, len);
	*retlen = len;
	return 0;
}

static int phram_write(struct mtd_info *mtd, loff_t to, size_t len,
		size_t *retlen, const u_char *buf)
{
	u_char *start = mtd->priv;

	memcpy(start + to, buf, len);
	*retlen = len;
	return 0;
}

static int phram_map(struct phram_mtd_list *phram, phys_addr_t start, size_t len)
{
	void *addr = NULL;

	if (phram->cached)
		addr = memremap(start, len, MEMREMAP_WB);
	else
		addr = (void __force *)ioremap(start, len);
	if (!addr)
		return -EIO;

	phram->mtd.priv = addr;

	return 0;
}

static void phram_unmap(struct phram_mtd_list *phram)
{
	void *addr = phram->mtd.priv;

	if (phram->cached) {
		memunmap(addr);
		return;
	}

	iounmap((void __iomem *)addr);
}

static void unregister_devices(void)
{
	struct phram_mtd_list *this, *safe;

	list_for_each_entry_safe(this, safe, &phram_list, list) {
		mtd_device_unregister(&this->mtd);
		phram_unmap(this);
		kfree(this->mtd.name);
		kfree(this);
	}
}

static int register_device(struct platform_device *pdev, const char *name,
			   phys_addr_t start, size_t len, uint32_t erasesize)
{
	struct device_node *np = pdev ? pdev->dev.of_node : NULL;
	bool cached = np ? !of_property_read_bool(np, "no-map") : false;
	struct phram_mtd_list *new;
	int ret = -ENOMEM;

	new = kzalloc(sizeof(*new), GFP_KERNEL);
	if (!new)
		goto out0;

	new->cached = cached;

	ret = phram_map(new, start, len);
	if (ret) {
		pr_err("ioremap failed\n");
		goto out1;
	}


	new->mtd.name = name;
	new->mtd.size = len;
	new->mtd.flags = MTD_CAP_RAM;
	new->mtd._erase = phram_erase;
	new->mtd._point = phram_point;
	new->mtd._unpoint = phram_unpoint;
	new->mtd._read = phram_read;
	new->mtd._write = phram_write;
	new->mtd.owner = THIS_MODULE;
	new->mtd.type = MTD_RAM;
	new->mtd.erasesize = erasesize;
	new->mtd.writesize = 1;

	mtd_set_of_node(&new->mtd, np);

	ret = -EAGAIN;
	if (mtd_device_register(&new->mtd, NULL, 0)) {
		pr_err("Failed to register new device\n");
		goto out2;
	}

	if (pdev)
		platform_set_drvdata(pdev, new);
	else
		list_add_tail(&new->list, &phram_list);

	return 0;

out2:
	phram_unmap(new);
out1:
	kfree(new);
out0:
	return ret;
}

static int parse_num64(uint64_t *num64, char *token)
{
	size_t len;
	int shift = 0;
	int ret;

	len = strlen(token);
	/* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
	if (len > 2) {
		if (token[len - 1] == 'i') {
			switch (token[len - 2]) {
			case 'G':
				shift += 10;
				fallthrough;
			case 'M':
				shift += 10;
				fallthrough;
			case 'k':
				shift += 10;
				token[len - 2] = 0;
				break;
			default:
				return -EINVAL;
			}
		}
	}

	ret = kstrtou64(token, 0, num64);
	*num64 <<= shift;

	return ret;
}

static int parse_name(char **pname, const char *token)
{
	size_t len;
	char *name;

	len = strlen(token) + 1;
	if (len > 64)
		return -ENOSPC;

	name = kstrdup(token, GFP_KERNEL);
	if (!name)
		return -ENOMEM;

	*pname = name;
	return 0;
}


static inline void kill_final_newline(char *str)
{
	char *newline = strrchr(str, '\n');

	if (newline && !newline[1])
		*newline = 0;
}


#define parse_err(fmt, args...) do {	\
	pr_err(fmt , ## args);	\
	return 1;		\
} while (0)

#ifndef MODULE
static int phram_init_called;
/*
 * This shall contain the module parameter if any. It is of the form:
 * - phram=<device>,<address>,<size>[,<erasesize>] for module case
 * - phram.phram=<device>,<address>,<size>[,<erasesize>] for built-in case
 * We leave 64 bytes for the device name, 20 for the address , 20 for the
 * size and 20 for the erasesize.
 * Example: phram.phram=rootfs,0xa0000000,512Mi,65536
 */
static char phram_paramline[64 + 20 + 20 + 20];
#endif

static int phram_setup(const char *val)
{
	char buf[64 + 20 + 20 + 20], *str = buf;
	char *token[4];
	char *name;
	uint64_t start;
	uint64_t len;
	uint64_t erasesize = PAGE_SIZE;
	uint32_t rem;
	int i, ret;

	if (strnlen(val, sizeof(buf)) >= sizeof(buf))
		parse_err("parameter too long\n");

	strcpy(str, val);
	kill_final_newline(str);

	for (i = 0; i < 4; i++)
		token[i] = strsep(&str, ",");

	if (str)
		parse_err("too many arguments\n");

	if (!token[2])
		parse_err("not enough arguments\n");

	ret = parse_name(&name, token[0]);
	if (ret)
		return ret;

	ret = parse_num64(&start, token[1]);
	if (ret) {
		parse_err("illegal start address\n");
		goto error;
	}

	ret = parse_num64(&len, token[2]);
	if (ret) {
		parse_err("illegal device length\n");
		goto error;
	}

	if (token[3]) {
		ret = parse_num64(&erasesize, token[3]);
		if (ret) {
			parse_err("illegal erasesize\n");
			goto error;
		}
	}

	if (len == 0 || erasesize == 0 || erasesize > len
	    || erasesize > UINT_MAX) {
		parse_err("illegal erasesize or len\n");
		ret = -EINVAL;
		goto error;
	}

	div_u64_rem(len, (uint32_t)erasesize, &rem);
	if (rem) {
		parse_err("len is not multiple of erasesize\n");
		ret = -EINVAL;
		goto error;
	}

	ret = register_device(NULL, name, start, len, (uint32_t)erasesize);
	if (ret)
		goto error;

	pr_info("%s device: %#llx at %#llx for erasesize %#llx\n", name, len, start, erasesize);
	return 0;

error:
	kfree(name);
	return ret;
}

static int phram_param_call(const char *val, const struct kernel_param *kp)
{
#ifdef MODULE
	return phram_setup(val);
#else
	/*
	 * If more parameters are later passed in via
	 * /sys/module/phram/parameters/phram
	 * and init_phram() has already been called,
	 * we can parse the argument now.
	 */

	if (phram_init_called)
		return phram_setup(val);

	/*
	 * During early boot stage, we only save the parameters
	 * here. We must parse them later: if the param passed
	 * from kernel boot command line, phram_param_call() is
	 * called so early that it is not possible to resolve
	 * the device (even kmalloc() fails). Defer that work to
	 * phram_setup().
	 */

	if (strlen(val) >= sizeof(phram_paramline))
		return -ENOSPC;
	strcpy(phram_paramline, val);

	return 0;
#endif
}

module_param_call(phram, phram_param_call, NULL, NULL, 0200);
MODULE_PARM_DESC(phram, "Memory region to map. \"phram=<name>,<start>,<length>[,<erasesize>]\"");

#ifdef CONFIG_OF
static const struct of_device_id phram_of_match[] = {
	{ .compatible = "phram" },
	{}
};
MODULE_DEVICE_TABLE(of, phram_of_match);
#endif

static int phram_probe(struct platform_device *pdev)
{
	struct resource *res;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
		return -ENOMEM;

	/* mtd_set_of_node() reads name from "label" */
	return register_device(pdev, NULL, res->start, resource_size(res),
			       PAGE_SIZE);
}

static void phram_remove(struct platform_device *pdev)
{
	struct phram_mtd_list *phram = platform_get_drvdata(pdev);

	mtd_device_unregister(&phram->mtd);
	phram_unmap(phram);
	kfree(phram);
}

static struct platform_driver phram_driver = {
	.probe		= phram_probe,
	.remove		= phram_remove,
	.driver		= {
		.name		= "phram",
		.of_match_table	= of_match_ptr(phram_of_match),
	},
};

static int __init init_phram(void)
{
	int ret;

	ret = platform_driver_register(&phram_driver);
	if (ret)
		return ret;

#ifndef MODULE
	if (phram_paramline[0])
		ret = phram_setup(phram_paramline);
	phram_init_called = 1;
#endif

	if (ret)
		platform_driver_unregister(&phram_driver);

	return ret;
}

static void __exit cleanup_phram(void)
{
	unregister_devices();
	platform_driver_unregister(&phram_driver);
}

module_init(init_phram);
module_exit(cleanup_phram);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Joern Engel <joern@wh.fh-wedel.de>");
MODULE_DESCRIPTION("MTD driver for physical RAM");