/*
   * 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
  ", 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
  ", 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 *file, loff_t offset, int origin)
  {
  	struct srom_dev *srom = file->private_data;
  	return fixed_size_llseek(file, offset, origin, srom->total_size);
  }
  
  static ssize_t total_size_show(struct device *dev,
  			       struct device_attribute *attr, char *buf)
  {
  	struct srom_dev *srom = dev_get_drvdata(dev);
  	return sprintf(buf, "%u
  ", srom->total_size);
  }
  static DEVICE_ATTR_RO(total_size);
  
  static ssize_t sector_size_show(struct device *dev,
  				struct device_attribute *attr, char *buf)
  {
  	struct srom_dev *srom = dev_get_drvdata(dev);
  	return sprintf(buf, "%u
  ", srom->sector_size);
  }
  static DEVICE_ATTR_RO(sector_size);
  
  static ssize_t page_size_show(struct device *dev,
  			      struct device_attribute *attr, char *buf)
  {
  	struct srom_dev *srom = dev_get_drvdata(dev);
  	return sprintf(buf, "%u
  ", srom->page_size);
  }
  static DEVICE_ATTR_RO(page_size);
  
  static struct attribute *srom_dev_attrs[] = {
  	&dev_attr_total_size.attr,
  	&dev_attr_sector_size.attr,
  	&dev_attr_page_size.attr,
  	NULL,
  };
  ATTRIBUTE_GROUPS(srom_dev);
  
  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 PTR_ERR_OR_ZERO(dev);
  }
  
  /** 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.
  ",
  					  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_groups = srom_dev_groups;
  	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);