/*
 * Copyright 2011 Tilera Corporation. All Rights Reserved.
 *
 *   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, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 *
 * SPI Flash ROM driver
 *
 * This source code is derived from code provided in "Linux Device
 * Drivers, Third Edition", by Jonathan Corbet, Alessandro Rubini, and
 * Greg Kroah-Hartman, published by O'Reilly Media, Inc.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h>       /* printk() */
#include <linux/slab.h>         /* kmalloc() */
#include <linux/fs.h>           /* everything... */
#include <linux/errno.h>        /* error codes */
#include <linux/types.h>        /* size_t */
#include <linux/proc_fs.h>
#include <linux/fcntl.h>        /* O_ACCMODE */
#include <linux/aio.h>
#include <linux/pagemap.h>
#include <linux/hugetlb.h>
#include <linux/uaccess.h>
#include <linux/platform_device.h>
#include <hv/hypervisor.h>
#include <linux/ioctl.h>
#include <linux/cdev.h>
#include <linux/delay.h>
#include <hv/drv_srom_intf.h>

/*
 * Size of our hypervisor I/O requests.  We break up large transfers
 * so that we don't spend large uninterrupted spans of time in the
 * hypervisor.  Erasing an SROM sector takes a significant fraction of
 * a second, so if we allowed the user to, say, do one I/O to write the
 * entire ROM, we'd get soft lockup timeouts, or worse.
 */
#define SROM_CHUNK_SIZE ((size_t)4096)

/*
 * When hypervisor is busy (e.g. erasing), poll the status periodically.
 */

/*
 * Interval to poll the state in msec
 */
#define SROM_WAIT_TRY_INTERVAL 20

/*
 * Maximum times to poll the state
 */
#define SROM_MAX_WAIT_TRY_TIMES 1000

struct srom_dev {
        int hv_devhdl;                  /* Handle for hypervisor device */
        u32 total_size;                 /* Size of this device */
        u32 sector_size;                /* Size of a sector */
        u32 page_size;                  /* Size of a page */
        struct mutex lock;              /* Allow only one accessor at a time */
};

static int srom_major;                  /* Dynamic major by default */
module_param(srom_major, int, 0);
MODULE_AUTHOR("Tilera Corporation");
MODULE_LICENSE("GPL");

static int srom_devs;                   /* Number of SROM partitions */
static struct cdev srom_cdev;
static struct class *srom_class;
static struct srom_dev *srom_devices;

/*
 * Handle calling the hypervisor and managing EAGAIN/EBUSY.
 */

static ssize_t _srom_read(int hv_devhdl, void *buf,
                          loff_t off, size_t count)
{
        int retval, retries = SROM_MAX_WAIT_TRY_TIMES;
        for (;;) {
                retval = hv_dev_pread(hv_devhdl, 0, (HV_VirtAddr)buf,
                                      count, off);
                if (retval >= 0)
                        return retval;
                if (retval == HV_EAGAIN)
                        continue;
                if (retval == HV_EBUSY && --retries > 0) {
                        msleep(SROM_WAIT_TRY_INTERVAL);
                        continue;
                }
                pr_err("_srom_read: error %d\n", retval);
                return -EIO;
        }
}

static ssize_t _srom_write(int hv_devhdl, const void *buf,
                           loff_t off, size_t count)
{
        int retval, retries = SROM_MAX_WAIT_TRY_TIMES;
        for (;;) {
                retval = hv_dev_pwrite(hv_devhdl, 0, (HV_VirtAddr)buf,
                                       count, off);
                if (retval >= 0)
                        return retval;
                if (retval == HV_EAGAIN)
                        continue;
                if (retval == HV_EBUSY && --retries > 0) {
                        msleep(SROM_WAIT_TRY_INTERVAL);
                        continue;
                }
                pr_err("_srom_write: error %d\n", retval);
                return -EIO;
        }
}

/**
 * srom_open() - Device open routine.
 * @inode: Inode for this device.
 * @filp: File for this specific open of the device.
 *
 * Returns zero, or an error code.
 */
static int srom_open(struct inode *inode, struct file *filp)
{
        filp->private_data = &srom_devices[iminor(inode)];
        return 0;
}


/**
 * srom_release() - Device release routine.
 * @inode: Inode for this device.
 * @filp: File for this specific open of the device.
 *
 * Returns zero, or an error code.
 */
static int srom_release(struct inode *inode, struct file *filp)
{
        struct srom_dev *srom = filp->private_data;
        char dummy;

        /* Make sure we've flushed anything written to the ROM. */
        mutex_lock(&srom->lock);
        if (srom->hv_devhdl >= 0)
                _srom_write(srom->hv_devhdl, &dummy, SROM_FLUSH_OFF, 1);
        mutex_unlock(&srom->lock);

        filp->private_data = NULL;

        return 0;
}


/**
 * srom_read() - Read data from the device.
 * @filp: File for this specific open of the device.
 * @buf: User's data buffer.
 * @count: Number of bytes requested.
 * @f_pos: File position.
 *
 * Returns number of bytes read, or an error code.
 */
static ssize_t srom_read(struct file *filp, char __user *buf,
                         size_t count, loff_t *f_pos)
{
        int retval = 0;
        void *kernbuf;
        struct srom_dev *srom = filp->private_data;

        kernbuf = kmalloc(SROM_CHUNK_SIZE, GFP_KERNEL);
        if (!kernbuf)
                return -ENOMEM;

        if (mutex_lock_interruptible(&srom->lock)) {
                retval = -ERESTARTSYS;
                kfree(kernbuf);
                return retval;
        }

        while (count) {
                int hv_retval;
                int bytes_this_pass = min(count, SROM_CHUNK_SIZE);

                hv_retval = _srom_read(srom->hv_devhdl, kernbuf,
                                       *f_pos, bytes_this_pass);
                if (hv_retval <= 0) {
                        if (retval == 0)
                                retval = hv_retval;
                        break;
                }

                if (copy_to_user(buf, kernbuf, hv_retval) != 0) {
                        retval = -EFAULT;
                        break;
                }

                retval += hv_retval;
                *f_pos += hv_retval;
                buf += hv_retval;
                count -= hv_retval;
        }

        mutex_unlock(&srom->lock);
        kfree(kernbuf);

        return retval;
}

/**
 * srom_write() - Write data to the device.
 * @filp: File for this specific open of the device.
 * @buf: User's data buffer.
 * @count: Number of bytes requested.
 * @f_pos: File position.
 *
 * Returns number of bytes written, or an error code.
 */
static ssize_t srom_write(struct file *filp, const char __user *buf,
                          size_t count, loff_t *f_pos)
{
        int retval = 0;
        void *kernbuf;
        struct srom_dev *srom = filp->private_data;

        kernbuf = kmalloc(SROM_CHUNK_SIZE, GFP_KERNEL);
        if (!kernbuf)
                return -ENOMEM;

        if (mutex_lock_interruptible(&srom->lock)) {
                retval = -ERESTARTSYS;
                kfree(kernbuf);
                return retval;
        }

        while (count) {
                int hv_retval;
                int bytes_this_pass = min(count, SROM_CHUNK_SIZE);

                if (copy_from_user(kernbuf, buf, bytes_this_pass) != 0) {
                        retval = -EFAULT;
                        break;
                }

                hv_retval = _srom_write(srom->hv_devhdl, kernbuf,
                                        *f_pos, bytes_this_pass);
                if (hv_retval <= 0) {
                        if (retval == 0)
                                retval = hv_retval;
                        break;
                }

                retval += hv_retval;
                *f_pos += hv_retval;
                buf += hv_retval;
                count -= hv_retval;
        }

        mutex_unlock(&srom->lock);
        kfree(kernbuf);

        return retval;
}

/* Provide our own implementation so we can use srom->total_size. */
loff_t srom_llseek(struct file *filp, loff_t offset, int origin)
{
        struct srom_dev *srom = filp->private_data;

        if (mutex_lock_interruptible(&srom->lock))
                return -ERESTARTSYS;

        switch (origin) {
        case SEEK_END:
                offset += srom->total_size;
                break;
        case SEEK_CUR:
                offset += filp->f_pos;
                break;
        }

        if (offset < 0 || offset > srom->total_size) {
                offset = -EINVAL;
        } else {
                filp->f_pos = offset;
                filp->f_version = 0;
        }

        mutex_unlock(&srom->lock);

        return offset;
}

static ssize_t total_show(struct device *dev,
                          struct device_attribute *attr, char *buf)
{
        struct srom_dev *srom = dev_get_drvdata(dev);
        return sprintf(buf, "%u\n", srom->total_size);
}

static ssize_t sector_show(struct device *dev,
                           struct device_attribute *attr, char *buf)
{
        struct srom_dev *srom = dev_get_drvdata(dev);
        return sprintf(buf, "%u\n", srom->sector_size);
}

static ssize_t page_show(struct device *dev,
                         struct device_attribute *attr, char *buf)
{
        struct srom_dev *srom = dev_get_drvdata(dev);
        return sprintf(buf, "%u\n", srom->page_size);
}

static struct device_attribute srom_dev_attrs[] = {
        __ATTR(total_size, S_IRUGO, total_show, NULL),
        __ATTR(sector_size, S_IRUGO, sector_show, NULL),
        __ATTR(page_size, S_IRUGO, page_show, NULL),
        __ATTR_NULL
};

static char *srom_devnode(struct device *dev, umode_t *mode)
{
        *mode = S_IRUGO | S_IWUSR;
        return kasprintf(GFP_KERNEL, "srom/%s", dev_name(dev));
}

/*
 * The fops
 */
static const struct file_operations srom_fops = {
        .owner =     THIS_MODULE,
        .llseek =    srom_llseek,
        .read =      srom_read,
        .write =     srom_write,
        .open =      srom_open,
        .release =   srom_release,
};

/**
 * srom_setup_minor() - Initialize per-minor information.
 * @srom: Per-device SROM state.
 * @index: Device to set up.
 */
static int srom_setup_minor(struct srom_dev *srom, int index)
{
        struct device *dev;
        int devhdl = srom->hv_devhdl;

        mutex_init(&srom->lock);

        if (_srom_read(devhdl, &srom->total_size,
                       SROM_TOTAL_SIZE_OFF, sizeof(srom->total_size)) < 0)
                return -EIO;
        if (_srom_read(devhdl, &srom->sector_size,
                       SROM_SECTOR_SIZE_OFF, sizeof(srom->sector_size)) < 0)
                return -EIO;
        if (_srom_read(devhdl, &srom->page_size,
                       SROM_PAGE_SIZE_OFF, sizeof(srom->page_size)) < 0)
                return -EIO;

        dev = device_create(srom_class, &platform_bus,
                            MKDEV(srom_major, index), srom, "%d", index);
        return IS_ERR(dev) ? PTR_ERR(dev) : 0;
}

/** srom_init() - Initialize the driver's module. */
static int srom_init(void)
{
        int result, i;
        dev_t dev = MKDEV(srom_major, 0);

        /*
         * Start with a plausible number of partitions; the krealloc() call
         * below will yield about log(srom_devs) additional allocations.
         */
        srom_devices = kzalloc(4 * sizeof(struct srom_dev), GFP_KERNEL);

        /* Discover the number of srom partitions. */
        for (i = 0; ; i++) {
                int devhdl;
                char buf[20];
                struct srom_dev *new_srom_devices =
                        krealloc(srom_devices, (i+1) * sizeof(struct srom_dev),
                                 GFP_KERNEL | __GFP_ZERO);
                if (!new_srom_devices) {
                        result = -ENOMEM;
                        goto fail_mem;
                }
                srom_devices = new_srom_devices;
                sprintf(buf, "srom/0/%d", i);
                devhdl = hv_dev_open((HV_VirtAddr)buf, 0);
                if (devhdl < 0) {
                        if (devhdl != HV_ENODEV)
                                pr_notice("srom/%d: hv_dev_open failed: %d.\n",
                                          i, devhdl);
                        break;
                }
                srom_devices[i].hv_devhdl = devhdl;
        }
        srom_devs = i;

        /* Bail out early if we have no partitions at all. */
        if (srom_devs == 0) {
                result = -ENODEV;
                goto fail_mem;
        }

        /* Register our major, and accept a dynamic number. */
        if (srom_major)
                result = register_chrdev_region(dev, srom_devs, "srom");
        else {
                result = alloc_chrdev_region(&dev, 0, srom_devs, "srom");
                srom_major = MAJOR(dev);
        }
        if (result < 0)
                goto fail_mem;

        /* Register a character device. */
        cdev_init(&srom_cdev, &srom_fops);
        srom_cdev.owner = THIS_MODULE;
        srom_cdev.ops = &srom_fops;
        result = cdev_add(&srom_cdev, dev, srom_devs);
        if (result < 0)
                goto fail_chrdev;

        /* Create a sysfs class. */
        srom_class = class_create(THIS_MODULE, "srom");
        if (IS_ERR(srom_class)) {
                result = PTR_ERR(srom_class);
                goto fail_cdev;
        }
        srom_class->dev_attrs = srom_dev_attrs;
        srom_class->devnode = srom_devnode;

        /* Do per-partition initialization */
        for (i = 0; i < srom_devs; i++) {
                result = srom_setup_minor(srom_devices + i, i);
                if (result < 0)
                        goto fail_class;
        }

        return 0;

fail_class:
        for (i = 0; i < srom_devs; i++)
                device_destroy(srom_class, MKDEV(srom_major, i));
        class_destroy(srom_class);
fail_cdev:
        cdev_del(&srom_cdev);
fail_chrdev:
        unregister_chrdev_region(dev, srom_devs);
fail_mem:
        kfree(srom_devices);
        return result;
}

/** srom_cleanup() - Clean up the driver's module. */
static void srom_cleanup(void)
{
        int i;
        for (i = 0; i < srom_devs; i++)
                device_destroy(srom_class, MKDEV(srom_major, i));
        class_destroy(srom_class);
        cdev_del(&srom_cdev);
        unregister_chrdev_region(MKDEV(srom_major, 0), srom_devs);
        kfree(srom_devices);
}

module_init(srom_init);
module_exit(srom_cleanup);