// SPDX-License-Identifier: GPL-2.0-only
/* flash.c: Allow mmap access to the OBP Flash, for OBP updates.
 *
 * Copyright (C) 1997  Eddie C. Dost  (ecd@skynet.be)
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/fcntl.h>
#include <linux/poll.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/of.h>
#include <linux/platform_device.h>

#include <linux/uaccess.h>
#include <asm/io.h>
#include <asm/upa.h>

static DEFINE_MUTEX(flash_mutex);
static DEFINE_SPINLOCK(flash_lock);
static struct {
        unsigned long read_base;        /* Physical read address */
        unsigned long write_base;       /* Physical write address */
        unsigned long read_size;        /* Size of read area */
        unsigned long write_size;       /* Size of write area */
        unsigned long busy;             /* In use? */
} flash;

static int
flash_mmap(struct file *file, struct vm_area_struct *vma)
{
        unsigned long addr;
        unsigned long size;

        spin_lock(&flash_lock);
        if (flash.read_base == flash.write_base) {
                addr = flash.read_base;
                size = flash.read_size;
        } else {
                if ((vma->vm_flags & VM_READ) &&
                    (vma->vm_flags & VM_WRITE)) {
                        spin_unlock(&flash_lock);
                        return -EINVAL;
                }
                if (vma->vm_flags & VM_READ) {
                        addr = flash.read_base;
                        size = flash.read_size;
                } else if (vma->vm_flags & VM_WRITE) {
                        addr = flash.write_base;
                        size = flash.write_size;
                } else {
                        spin_unlock(&flash_lock);
                        return -ENXIO;
                }
        }
        spin_unlock(&flash_lock);

        if ((vma->vm_pgoff << PAGE_SHIFT) > size)
                return -ENXIO;
        addr = vma->vm_pgoff + (addr >> PAGE_SHIFT);

        if (vma->vm_end - (vma->vm_start + (vma->vm_pgoff << PAGE_SHIFT)) > size)
                size = vma->vm_end - (vma->vm_start + (vma->vm_pgoff << PAGE_SHIFT));

        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

        if (io_remap_pfn_range(vma, vma->vm_start, addr, size, vma->vm_page_prot))
                return -EAGAIN;
                
        return 0;
}

static long long
flash_llseek(struct file *file, long long offset, int origin)
{
        mutex_lock(&flash_mutex);
        switch (origin) {
                case 0:
                        file->f_pos = offset;
                        break;
                case 1:
                        file->f_pos += offset;
                        if (file->f_pos > flash.read_size)
                                file->f_pos = flash.read_size;
                        break;
                case 2:
                        file->f_pos = flash.read_size;
                        break;
                default:
                        mutex_unlock(&flash_mutex);
                        return -EINVAL;
        }
        mutex_unlock(&flash_mutex);
        return file->f_pos;
}

static ssize_t
flash_read(struct file * file, char __user * buf,
           size_t count, loff_t *ppos)
{
        loff_t p = *ppos;
        int i;

        if (count > flash.read_size - p)
                count = flash.read_size - p;

        for (i = 0; i < count; i++) {
                u8 data = upa_readb(flash.read_base + p + i);
                if (put_user(data, buf))
                        return -EFAULT;
                buf++;
        }

        *ppos += count;
        return count;
}

static int
flash_open(struct inode *inode, struct file *file)
{
        mutex_lock(&flash_mutex);
        if (test_and_set_bit(0, (void *)&flash.busy) != 0) {
                mutex_unlock(&flash_mutex);
                return -EBUSY;
        }

        mutex_unlock(&flash_mutex);
        return 0;
}

static int
flash_release(struct inode *inode, struct file *file)
{
        spin_lock(&flash_lock);
        flash.busy = 0;
        spin_unlock(&flash_lock);

        return 0;
}

static const struct file_operations flash_fops = {
        /* no write to the Flash, use mmap
         * and play flash dependent tricks.
         */
        .owner =        THIS_MODULE,
        .llseek =       flash_llseek,
        .read =         flash_read,
        .mmap =         flash_mmap,
        .open =         flash_open,
        .release =      flash_release,
};

static struct miscdevice flash_dev = { SBUS_FLASH_MINOR, "flash", &flash_fops };

static int flash_probe(struct platform_device *op)
{
        struct device_node *dp = op->dev.of_node;
        struct device_node *parent;

        parent = dp->parent;

        if (!of_node_name_eq(parent, "sbus") &&
            !of_node_name_eq(parent, "sbi") &&
            !of_node_name_eq(parent, "ebus"))
                return -ENODEV;

        flash.read_base = op->resource[0].start;
        flash.read_size = resource_size(&op->resource[0]);
        if (op->resource[1].flags) {
                flash.write_base = op->resource[1].start;
                flash.write_size = resource_size(&op->resource[1]);
        } else {
                flash.write_base = op->resource[0].start;
                flash.write_size = resource_size(&op->resource[0]);
        }
        flash.busy = 0;

        printk(KERN_INFO "%pOF: OBP Flash, RD %lx[%lx] WR %lx[%lx]\n",
               op->dev.of_node,
               flash.read_base, flash.read_size,
               flash.write_base, flash.write_size);

        return misc_register(&flash_dev);
}

static void flash_remove(struct platform_device *op)
{
        misc_deregister(&flash_dev);
}

static const struct of_device_id flash_match[] = {
        {
                .name = "flashprom",
        },
        {},
};
MODULE_DEVICE_TABLE(of, flash_match);

static struct platform_driver flash_driver = {
        .driver = {
                .name = "flash",
                .of_match_table = flash_match,
        },
        .probe          = flash_probe,
        .remove         = flash_remove,
};

module_platform_driver(flash_driver);

MODULE_DESCRIPTION("OBP Flash Device driver");
MODULE_LICENSE("GPL");