// SPDX-License-Identifier: GPL-2.0-only
/*
 * Flash memory interface rev.5 driver for the Intel
 * Flash chips used on the NetWinder.
 *
 * 20/08/2000   RMK     use __ioremap to map flash into virtual memory
 *                      make a few more places use "volatile"
 * 22/05/2001   RMK     - Lock read against write
 *                      - merge printk level changes (with mods) from Alan Cox.
 *                      - use *ppos as the file position, not file->f_pos.
 *                      - fix check for out of range pos and r/w size
 *
 * Please note that we are tampering with the only flash chip in the
 * machine, which contains the bootup code.  We therefore have the
 * power to convert these machines into doorstops...
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/proc_fs.h>
#include <linux/miscdevice.h>
#include <linux/spinlock.h>
#include <linux/rwsem.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/jiffies.h>

#include <asm/hardware/dec21285.h>
#include <asm/io.h>
#include <asm/mach-types.h>
#include <linux/uaccess.h>

/*****************************************************************************/
#include <asm/nwflash.h>

#define NWFLASH_VERSION "6.4"

static DEFINE_MUTEX(flash_mutex);
static void kick_open(void);
static int get_flash_id(void);
static int erase_block(int nBlock);
static int write_block(unsigned long p, const char __user *buf, int count);

#define KFLASH_SIZE     1024*1024       //1 Meg
#define KFLASH_SIZE4    4*1024*1024     //4 Meg
#define KFLASH_ID       0x89A6          //Intel flash
#define KFLASH_ID4      0xB0D4          //Intel flash 4Meg

static bool flashdebug;         //if set - we will display progress msgs

static int gbWriteEnable;
static int gbWriteBase64Enable;
static volatile unsigned char *FLASH_BASE;
static int gbFlashSize = KFLASH_SIZE;
static DEFINE_MUTEX(nwflash_mutex);

static int get_flash_id(void)
{
        volatile unsigned int c1, c2;

        /*
         * try to get flash chip ID
         */
        kick_open();
        c2 = inb(0x80);
        *(volatile unsigned char *) (FLASH_BASE + 0x8000) = 0x90;
        udelay(15);
        c1 = *(volatile unsigned char *) FLASH_BASE;
        c2 = inb(0x80);

        /*
         * on 4 Meg flash the second byte is actually at offset 2...
         */
        if (c1 == 0xB0)
                c2 = *(volatile unsigned char *) (FLASH_BASE + 2);
        else
                c2 = *(volatile unsigned char *) (FLASH_BASE + 1);

        c2 += (c1 << 8);

        /*
         * set it back to read mode
         */
        *(volatile unsigned char *) (FLASH_BASE + 0x8000) = 0xFF;

        if (c2 == KFLASH_ID4)
                gbFlashSize = KFLASH_SIZE4;

        return c2;
}

static long flash_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
{
        mutex_lock(&flash_mutex);
        switch (cmd) {
        case CMD_WRITE_DISABLE:
                gbWriteBase64Enable = 0;
                gbWriteEnable = 0;
                break;

        case CMD_WRITE_ENABLE:
                gbWriteEnable = 1;
                break;

        case CMD_WRITE_BASE64K_ENABLE:
                gbWriteBase64Enable = 1;
                break;

        default:
                gbWriteBase64Enable = 0;
                gbWriteEnable = 0;
                mutex_unlock(&flash_mutex);
                return -EINVAL;
        }
        mutex_unlock(&flash_mutex);
        return 0;
}

static ssize_t flash_read(struct file *file, char __user *buf, size_t size,
                          loff_t *ppos)
{
        ssize_t ret;

        if (flashdebug)
                printk(KERN_DEBUG "flash_read: flash_read: offset=0x%llx, "
                       "buffer=%p, count=0x%zx.\n", *ppos, buf, size);
        /*
         * We now lock against reads and writes. --rmk
         */
        if (mutex_lock_interruptible(&nwflash_mutex))
                return -ERESTARTSYS;

        ret = simple_read_from_buffer(buf, size, ppos, (void *)FLASH_BASE, gbFlashSize);
        mutex_unlock(&nwflash_mutex);

        return ret;
}

static ssize_t flash_write(struct file *file, const char __user *buf,
                           size_t size, loff_t * ppos)
{
        unsigned long p = *ppos;
        unsigned int count = size;
        int written;
        int nBlock, temp, rc;
        int i, j;

        if (flashdebug)
                printk("flash_write: offset=0x%lX, buffer=0x%p, count=0x%X.\n",
                       p, buf, count);

        if (!gbWriteEnable)
                return -EINVAL;

        if (p < 64 * 1024 && (!gbWriteBase64Enable))
                return -EINVAL;

        /*
         * check for out of range pos or count
         */
        if (p >= gbFlashSize)
                return count ? -ENXIO : 0;

        if (count > gbFlashSize - p)
                count = gbFlashSize - p;
                        
        if (!access_ok(buf, count))
                return -EFAULT;

        /*
         * We now lock against reads and writes. --rmk
         */
        if (mutex_lock_interruptible(&nwflash_mutex))
                return -ERESTARTSYS;

        written = 0;

        nBlock = (int) p >> 16; //block # of 64K bytes

        /*
         * # of 64K blocks to erase and write
         */
        temp = ((int) (p + count) >> 16) - nBlock + 1;

        /*
         * write ends at exactly 64k boundary?
         */
        if (((int) (p + count) & 0xFFFF) == 0)
                temp -= 1;

        if (flashdebug)
                printk(KERN_DEBUG "flash_write: writing %d block(s) "
                        "starting at %d.\n", temp, nBlock);

        for (; temp; temp--, nBlock++) {
                if (flashdebug)
                        printk(KERN_DEBUG "flash_write: erasing block %d.\n", nBlock);

                /*
                 * first we have to erase the block(s), where we will write...
                 */
                i = 0;
                j = 0;
          RetryBlock:
                do {
                        rc = erase_block(nBlock);
                        i++;
                } while (rc && i < 10);

                if (rc) {
                        printk(KERN_ERR "flash_write: erase error %x\n", rc);
                        break;
                }
                if (flashdebug)
                        printk(KERN_DEBUG "flash_write: writing offset %lX, "
                               "from buf %p, bytes left %X.\n", p, buf,
                               count - written);

                /*
                 * write_block will limit write to space left in this block
                 */
                rc = write_block(p, buf, count - written);
                j++;

                /*
                 * if somehow write verify failed? Can't happen??
                 */
                if (!rc) {
                        /*
                         * retry up to 10 times
                         */
                        if (j < 10)
                                goto RetryBlock;
                        else
                                /*
                                 * else quit with error...
                                 */
                                rc = -1;

                }
                if (rc < 0) {
                        printk(KERN_ERR "flash_write: write error %X\n", rc);
                        break;
                }
                p += rc;
                buf += rc;
                written += rc;
                *ppos += rc;

                if (flashdebug)
                        printk(KERN_DEBUG "flash_write: written 0x%X bytes OK.\n", written);
        }

        mutex_unlock(&nwflash_mutex);

        return written;
}


/*
 * The memory devices use the full 32/64 bits of the offset, and so we cannot
 * check against negative addresses: they are ok. The return value is weird,
 * though, in that case (0).
 *
 * also note that seeking relative to the "end of file" isn't supported:
 * it has no meaning, so it returns -EINVAL.
 */
static loff_t flash_llseek(struct file *file, loff_t offset, int orig)
{
        loff_t ret;

        mutex_lock(&flash_mutex);
        if (flashdebug)
                printk(KERN_DEBUG "flash_llseek: offset=0x%X, orig=0x%X.\n",
                       (unsigned int) offset, orig);

        ret = no_seek_end_llseek_size(file, offset, orig, gbFlashSize);
        mutex_unlock(&flash_mutex);
        return ret;
}


/*
 * assume that main Write routine did the parameter checking...
 * so just go ahead and erase, what requested!
 */

static int erase_block(int nBlock)
{
        volatile unsigned int c1;
        volatile unsigned char *pWritePtr;
        unsigned long timeout;
        int temp, temp1;

        /*
         * reset footbridge to the correct offset 0 (...0..3)
         */
        *CSR_ROMWRITEREG = 0;

        /*
         * dummy ROM read
         */
        c1 = *(volatile unsigned char *) (FLASH_BASE + 0x8000);

        kick_open();
        /*
         * reset status if old errors
         */
        *(volatile unsigned char *) (FLASH_BASE + 0x8000) = 0x50;

        /*
         * erase a block...
         * aim at the middle of a current block...
         */
        pWritePtr = (unsigned char *) ((unsigned int) (FLASH_BASE + 0x8000 + (nBlock << 16)));
        /*
         * dummy read
         */
        c1 = *pWritePtr;

        kick_open();
        /*
         * erase
         */
        *(volatile unsigned char *) pWritePtr = 0x20;

        /*
         * confirm
         */
        *(volatile unsigned char *) pWritePtr = 0xD0;

        /*
         * wait 10 ms
         */
        msleep(10);

        /*
         * wait while erasing in process (up to 10 sec)
         */
        timeout = jiffies + 10 * HZ;
        c1 = 0;
        while (!(c1 & 0x80) && time_before(jiffies, timeout)) {
                msleep(10);
                /*
                 * read any address
                 */
                c1 = *(volatile unsigned char *) (pWritePtr);
                //              printk("Flash_erase: status=%X.\n",c1);
        }

        /*
         * set flash for normal read access
         */
        kick_open();
//      *(volatile unsigned char*)(FLASH_BASE+0x8000) = 0xFF;
        *(volatile unsigned char *) pWritePtr = 0xFF;   //back to normal operation

        /*
         * check if erase errors were reported
         */
        if (c1 & 0x20) {
                printk(KERN_ERR "flash_erase: err at %p\n", pWritePtr);

                /*
                 * reset error
                 */
                *(volatile unsigned char *) (FLASH_BASE + 0x8000) = 0x50;
                return -2;
        }

        /*
         * just to make sure - verify if erased OK...
         */
        msleep(10);

        pWritePtr = (unsigned char *) ((unsigned int) (FLASH_BASE + (nBlock << 16)));

        for (temp = 0; temp < 16 * 1024; temp++, pWritePtr += 4) {
                if ((temp1 = *(volatile unsigned int *) pWritePtr) != 0xFFFFFFFF) {
                        printk(KERN_ERR "flash_erase: verify err at %p = %X\n",
                               pWritePtr, temp1);
                        return -1;
                }
        }

        return 0;

}

/*
 * write_block will limit number of bytes written to the space in this block
 */
static int write_block(unsigned long p, const char __user *buf, int count)
{
        volatile unsigned int c1;
        volatile unsigned int c2;
        unsigned char *pWritePtr;
        unsigned int uAddress;
        unsigned int offset;
        unsigned long timeout;
        unsigned long timeout1;

        pWritePtr = (unsigned char *) ((unsigned int) (FLASH_BASE + p));

        /*
         * check if write will end in this block....
         */
        offset = p & 0xFFFF;

        if (offset + count > 0x10000)
                count = 0x10000 - offset;

        /*
         * wait up to 30 sec for this block
         */
        timeout = jiffies + 30 * HZ;

        for (offset = 0; offset < count; offset++, pWritePtr++) {
                uAddress = (unsigned int) pWritePtr;
                uAddress &= 0xFFFFFFFC;
                if (__get_user(c2, buf + offset))
                        return -EFAULT;

          WriteRetry:
                /*
                 * dummy read
                 */
                c1 = *(volatile unsigned char *) (FLASH_BASE + 0x8000);

                /*
                 * kick open the write gate
                 */
                kick_open();

                /*
                 * program footbridge to the correct offset...0..3
                 */
                *CSR_ROMWRITEREG = (unsigned int) pWritePtr & 3;

                /*
                 * write cmd
                 */
                *(volatile unsigned char *) (uAddress) = 0x40;

                /*
                 * data to write
                 */
                *(volatile unsigned char *) (uAddress) = c2;

                /*
                 * get status
                 */
                *(volatile unsigned char *) (FLASH_BASE + 0x10000) = 0x70;

                c1 = 0;

                /*
                 * wait up to 1 sec for this byte
                 */
                timeout1 = jiffies + 1 * HZ;

                /*
                 * while not ready...
                 */
                while (!(c1 & 0x80) && time_before(jiffies, timeout1))
                        c1 = *(volatile unsigned char *) (FLASH_BASE + 0x8000);

                /*
                 * if timeout getting status
                 */
                if (time_after_eq(jiffies, timeout1)) {
                        kick_open();
                        /*
                         * reset err
                         */
                        *(volatile unsigned char *) (FLASH_BASE + 0x8000) = 0x50;

                        goto WriteRetry;
                }
                /*
                 * switch on read access, as a default flash operation mode
                 */
                kick_open();
                /*
                 * read access
                 */
                *(volatile unsigned char *) (FLASH_BASE + 0x8000) = 0xFF;

                /*
                 * if hardware reports an error writing, and not timeout - 
                 * reset the chip and retry
                 */
                if (c1 & 0x10) {
                        kick_open();
                        /*
                         * reset err
                         */
                        *(volatile unsigned char *) (FLASH_BASE + 0x8000) = 0x50;

                        /*
                         * before timeout?
                         */
                        if (time_before(jiffies, timeout)) {
                                if (flashdebug)
                                        printk(KERN_DEBUG "write_block: Retrying write at 0x%X)n",
                                               pWritePtr - FLASH_BASE);

                                /*
                                 * wait couple ms
                                 */
                                msleep(10);

                                goto WriteRetry;
                        } else {
                                printk(KERN_ERR "write_block: timeout at 0x%X\n",
                                       pWritePtr - FLASH_BASE);
                                /*
                                 * return error -2
                                 */
                                return -2;

                        }
                }
        }

        msleep(10);

        pWritePtr = (unsigned char *) ((unsigned int) (FLASH_BASE + p));

        for (offset = 0; offset < count; offset++) {
                char c, c1;
                if (__get_user(c, buf))
                        return -EFAULT;
                buf++;
                if ((c1 = *pWritePtr++) != c) {
                        printk(KERN_ERR "write_block: verify error at 0x%X (%02X!=%02X)\n",
                               pWritePtr - FLASH_BASE, c1, c);
                        return 0;
                }
        }

        return count;
}


static void kick_open(void)
{
        unsigned long flags;

        /*
         * we want to write a bit pattern XXX1 to Xilinx to enable
         * the write gate, which will be open for about the next 2ms.
         */
        raw_spin_lock_irqsave(&nw_gpio_lock, flags);
        nw_cpld_modify(CPLD_FLASH_WR_ENABLE, CPLD_FLASH_WR_ENABLE);
        raw_spin_unlock_irqrestore(&nw_gpio_lock, flags);

        /*
         * let the ISA bus to catch on...
         */
        udelay(25);
}

static const struct file_operations flash_fops =
{
        .owner          = THIS_MODULE,
        .llseek         = flash_llseek,
        .read           = flash_read,
        .write          = flash_write,
        .unlocked_ioctl = flash_ioctl,
};

static struct miscdevice flash_miscdev =
{
        NWFLASH_MINOR,
        "nwflash",
        &flash_fops
};

static int __init nwflash_init(void)
{
        int ret = -ENODEV;

        if (machine_is_netwinder()) {
                int id;

                FLASH_BASE = ioremap(DC21285_FLASH, KFLASH_SIZE4);
                if (!FLASH_BASE)
                        goto out;

                id = get_flash_id();
                if ((id != KFLASH_ID) && (id != KFLASH_ID4)) {
                        ret = -ENXIO;
                        iounmap((void *)FLASH_BASE);
                        printk("Flash: incorrect ID 0x%04X.\n", id);
                        goto out;
                }

                printk("Flash ROM driver v.%s, flash device ID 0x%04X, size %d Mb.\n",
                       NWFLASH_VERSION, id, gbFlashSize / (1024 * 1024));

                ret = misc_register(&flash_miscdev);
                if (ret < 0) {
                        iounmap((void *)FLASH_BASE);
                }
        }
out:
        return ret;
}

static void __exit nwflash_exit(void)
{
        misc_deregister(&flash_miscdev);
        iounmap((void *)FLASH_BASE);
}

MODULE_LICENSE("GPL");

module_param(flashdebug, bool, 0644);

module_init(nwflash_init);
module_exit(nwflash_exit);