// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * memory mapped NVRAM
 *
 * (C) Copyright IBM Corp. 2005
 *
 * Authors : Utz Bacher <utz.bacher@de.ibm.com>
 */

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/of_address.h>
#include <linux/spinlock.h>
#include <linux/types.h>

#include <asm/machdep.h>
#include <asm/nvram.h>

static void __iomem *mmio_nvram_start;
static long mmio_nvram_len;
static DEFINE_SPINLOCK(mmio_nvram_lock);

static ssize_t mmio_nvram_read(char *buf, size_t count, loff_t *index)
{
        unsigned long flags;

        if (*index >= mmio_nvram_len)
                return 0;
        if (*index + count > mmio_nvram_len)
                count = mmio_nvram_len - *index;

        spin_lock_irqsave(&mmio_nvram_lock, flags);

        memcpy_fromio(buf, mmio_nvram_start + *index, count);

        spin_unlock_irqrestore(&mmio_nvram_lock, flags);
        
        *index += count;
        return count;
}

static unsigned char mmio_nvram_read_val(int addr)
{
        unsigned long flags;
        unsigned char val;

        if (addr >= mmio_nvram_len)
                return 0xff;

        spin_lock_irqsave(&mmio_nvram_lock, flags);

        val = ioread8(mmio_nvram_start + addr);

        spin_unlock_irqrestore(&mmio_nvram_lock, flags);

        return val;
}

static ssize_t mmio_nvram_write(char *buf, size_t count, loff_t *index)
{
        unsigned long flags;

        if (*index >= mmio_nvram_len)
                return 0;
        if (*index + count > mmio_nvram_len)
                count = mmio_nvram_len - *index;

        spin_lock_irqsave(&mmio_nvram_lock, flags);

        memcpy_toio(mmio_nvram_start + *index, buf, count);

        spin_unlock_irqrestore(&mmio_nvram_lock, flags);
        
        *index += count;
        return count;
}

static void mmio_nvram_write_val(int addr, unsigned char val)
{
        unsigned long flags;

        if (addr < mmio_nvram_len) {
                spin_lock_irqsave(&mmio_nvram_lock, flags);

                iowrite8(val, mmio_nvram_start + addr);

                spin_unlock_irqrestore(&mmio_nvram_lock, flags);
        }
}

static ssize_t mmio_nvram_get_size(void)
{
        return mmio_nvram_len;
}

int __init mmio_nvram_init(void)
{
        struct device_node *nvram_node;
        unsigned long nvram_addr;
        struct resource r;
        int ret;

        nvram_node = of_find_node_by_type(NULL, "nvram");
        if (!nvram_node)
                nvram_node = of_find_compatible_node(NULL, NULL, "nvram");
        if (!nvram_node) {
                printk(KERN_WARNING "nvram: no node found in device-tree\n");
                return -ENODEV;
        }

        ret = of_address_to_resource(nvram_node, 0, &r);
        if (ret) {
                printk(KERN_WARNING "nvram: failed to get address (err %d)\n",
                       ret);
                goto out;
        }
        nvram_addr = r.start;
        mmio_nvram_len = resource_size(&r);
        if ( (!mmio_nvram_len) || (!nvram_addr) ) {
                printk(KERN_WARNING "nvram: address or length is 0\n");
                ret = -EIO;
                goto out;
        }

        mmio_nvram_start = ioremap(nvram_addr, mmio_nvram_len);
        if (!mmio_nvram_start) {
                printk(KERN_WARNING "nvram: failed to ioremap\n");
                ret = -ENOMEM;
                goto out;
        }

        printk(KERN_INFO "mmio NVRAM, %luk at 0x%lx mapped to %p\n",
               mmio_nvram_len >> 10, nvram_addr, mmio_nvram_start);

        ppc_md.nvram_read_val   = mmio_nvram_read_val;
        ppc_md.nvram_write_val  = mmio_nvram_write_val;
        ppc_md.nvram_read       = mmio_nvram_read;
        ppc_md.nvram_write      = mmio_nvram_write;
        ppc_md.nvram_size       = mmio_nvram_get_size;

out:
        of_node_put(nvram_node);
        return ret;
}