/*
   * Copyright (C) 2005 MIPS Technologies, Inc.  All rights reserved.

   * Copyright (C) 2005, 06 Ralf Baechle (ralf@linux-mips.org)

   *
   *  This program is free software; you can distribute it and/or modify it
   *  under the terms of the GNU General Public License (Version 2) as
   *  published by the Free Software Foundation.
   *
   *  This program is distributed in the hope it will be useful, but WITHOUT
   *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   *  for more details.
   *
   *  You should have received a copy of the GNU General Public License along
   *  with this program; if not, write to the Free Software Foundation, Inc.,
   *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
   *
   */

  #include <linux/device.h>

  #include <linux/kernel.h>

  #include <linux/fs.h>
  #include <linux/init.h>

  #include <asm/uaccess.h>

  #include <linux/list.h>
  #include <linux/vmalloc.h>
  #include <linux/elf.h>
  #include <linux/seq_file.h>
  #include <linux/syscalls.h>
  #include <linux/moduleloader.h>

  #include <linux/interrupt.h>

  #include <linux/poll.h>
  #include <linux/sched.h>
  #include <linux/wait.h>
  #include <asm/mipsmtregs.h>

  #include <asm/mips_mt.h>

  #include <asm/cacheflush.h>

  #include <linux/atomic.h>

  #include <asm/cpu.h>
  #include <asm/processor.h>

  #include <asm/system.h>
  #include <asm/vpe.h>

  #include <asm/rtlx.h>

  static struct rtlx_info *rtlx;

  static int major;
  static char module_name[] = "rtlx";

  
  static struct chan_waitqueues {
  	wait_queue_head_t rt_queue;
  	wait_queue_head_t lx_queue;

  	atomic_t in_open;

  	struct mutex mutex;

  } channel_wqs[RTLX_CHANNELS];

  static struct vpe_notifications notify;

  static int sp_stopping;

  extern void *vpe_get_shared(int index);

  static void rtlx_dispatch(void)

  {

  	do_IRQ(MIPS_CPU_IRQ_BASE + MIPS_CPU_RTLX_IRQ);

  }

  
  /* Interrupt handler may be called before rtlx_init has otherwise had
     a chance to run.
  */

  static irqreturn_t rtlx_interrupt(int irq, void *dev_id)

  {

  	unsigned int vpeflags;
  	unsigned long flags;

  	int i;

  
  	/* Ought not to be strictly necessary for SMTC builds */
  	local_irq_save(flags);
  	vpeflags = dvpe();
  	set_c0_status(0x100 << MIPS_CPU_RTLX_IRQ);
  	irq_enable_hazard();
  	evpe(vpeflags);
  	local_irq_restore(flags);

  
  	for (i = 0; i < RTLX_CHANNELS; i++) {

  			wake_up(&channel_wqs[i].lx_queue);
  			wake_up(&channel_wqs[i].rt_queue);

  	}

  	return IRQ_HANDLED;

  }

  static void __used dump_rtlx(void)

  {
  	int i;

  	printk("id 0x%lx state %d
  ", rtlx->id, rtlx->state);

  	for (i = 0; i < RTLX_CHANNELS; i++) {

  		struct rtlx_channel *chan = &rtlx->channel[i];

  		printk(" rt_state %d lx_state %d buffer_size %d
  ",
  		       chan->rt_state, chan->lx_state, chan->buffer_size);

  		printk(" rt_read %d rt_write %d
  ",
  		       chan->rt_read, chan->rt_write);

  		printk(" lx_read %d lx_write %d
  ",
  		       chan->lx_read, chan->lx_write);
  
  		printk(" rt_buffer <%s>
  ", chan->rt_buffer);
  		printk(" lx_buffer <%s>
  ", chan->lx_buffer);
  	}
  }
  
  /* call when we have the address of the shared structure from the SP side. */
  static int rtlx_init(struct rtlx_info *rtlxi)
  {
  	if (rtlxi->id != RTLX_ID) {

  		printk(KERN_ERR "no valid RTLX id at 0x%p 0x%lx
  ",
  			rtlxi, rtlxi->id);

  		return -ENOEXEC;
  	}

  
  	rtlx = rtlxi;

  
  	return 0;

  }

  /* notifications */
  static void starting(int vpe)

  {

  	int i;
  	sp_stopping = 0;
  
  	/* force a reload of rtlx */
  	rtlx=NULL;
  
  	/* wake up any sleeping rtlx_open's */
  	for (i = 0; i < RTLX_CHANNELS; i++)
  		wake_up_interruptible(&channel_wqs[i].lx_queue);
  }
  
  static void stopping(int vpe)
  {
  	int i;
  
  	sp_stopping = 1;
  	for (i = 0; i < RTLX_CHANNELS; i++)
  		wake_up_interruptible(&channel_wqs[i].lx_queue);
  }
  
  
  int rtlx_open(int index, int can_sleep)
  {

  	struct rtlx_info **p;

  	struct rtlx_channel *chan;

  	enum rtlx_state state;

  	int ret = 0;

  	if (index >= RTLX_CHANNELS) {
  		printk(KERN_DEBUG "rtlx_open index out of range
  ");
  		return -ENOSYS;
  	}

  	if (atomic_inc_return(&channel_wqs[index].in_open) > 1) {
  		printk(KERN_DEBUG "rtlx_open channel %d already opened
  ",
  		       index);
  		ret = -EBUSY;
  		goto out_fail;

  	}

  	if (rtlx == NULL) {

  		if( (p = vpe_get_shared(tclimit)) == NULL) {

  		    if (can_sleep) {
  			__wait_event_interruptible(channel_wqs[index].lx_queue,
  				(p = vpe_get_shared(tclimit)), ret);
  			if (ret)

  				goto out_fail;

  		    } else {
  			printk(KERN_DEBUG "No SP program loaded, and device "
  					"opened with O_NONBLOCK
  ");
  			ret = -ENOSYS;
  			goto out_fail;
  		    }

  		}

  		smp_rmb();

  		if (*p == NULL) {

  			if (can_sleep) {

  				DEFINE_WAIT(wait);
  
  				for (;;) {

  					prepare_to_wait(
  						&channel_wqs[index].lx_queue,
  						&wait, TASK_INTERRUPTIBLE);

  					smp_rmb();
  					if (*p != NULL)
  						break;
  					if (!signal_pending(current)) {
  						schedule();
  						continue;
  					}
  					ret = -ERESTARTSYS;

  					goto out_fail;

  				}
  				finish_wait(&channel_wqs[index].lx_queue, &wait);

  			} else {

  				pr_err(" *vpe_get_shared is NULL. "

  				       "Has an SP program been loaded?
  ");

  				ret = -ENOSYS;
  				goto out_fail;

  			}
  		}
  
  		if ((unsigned int)*p < KSEG0) {

  			printk(KERN_WARNING "vpe_get_shared returned an "
  			       "invalid pointer maybe an error code %d
  ",
  			       (int)*p);

  			ret = -ENOSYS;
  			goto out_fail;

  		}

  		if ((ret = rtlx_init(*p)) < 0)
  			goto out_ret;

  	}

  	chan = &rtlx->channel[index];

  	state = xchg(&chan->lx_state, RTLX_STATE_OPENED);
  	if (state == RTLX_STATE_OPENED) {
  		ret = -EBUSY;
  		goto out_fail;
  	}

  
  out_fail:

  	smp_mb();
  	atomic_dec(&channel_wqs[index].in_open);
  	smp_mb();

  out_ret:

  	return ret;

  }

  int rtlx_release(int index)

  {

  	if (rtlx == NULL) {
  		pr_err("rtlx_release() with null rtlx
  ");
  		return 0;
  	}

  	rtlx->channel[index].lx_state = RTLX_STATE_UNUSED;

  	return 0;

  }

  unsigned int rtlx_read_poll(int index, int can_sleep)

  {

   	struct rtlx_channel *chan;

   	if (rtlx == NULL)
   		return 0;

   	chan = &rtlx->channel[index];

  
  	/* data available to read? */

  	if (chan->lx_read == chan->lx_write) {
  		if (can_sleep) {

  			int ret = 0;

  			__wait_event_interruptible(channel_wqs[index].lx_queue,

  				(chan->lx_read != chan->lx_write) ||
  				sp_stopping, ret);

  			if (ret)
  				return ret;

  			if (sp_stopping)
  				return 0;
  		} else

  			return 0;
  	}
  
  	return (chan->lx_write + chan->buffer_size - chan->lx_read)
  	       % chan->buffer_size;

  }

  static inline int write_spacefree(int read, int write, int size)

  {

  	if (read == write) {
  		/*
  		 * Never fill the buffer completely, so indexes are always
  		 * equal if empty and only empty, or !equal if data available
  		 */
  		return size - 1;
  	}

  	return ((read + size - write) % size) - 1;
  }

  unsigned int rtlx_write_poll(int index)
  {
  	struct rtlx_channel *chan = &rtlx->channel[index];

  
  	return write_spacefree(chan->rt_read, chan->rt_write,
  				chan->buffer_size);

  }

  ssize_t rtlx_read(int index, void __user *buff, size_t count)

  {

  	size_t lx_write, fl = 0L;

  	struct rtlx_channel *lx;

  	unsigned long failed;

  	if (rtlx == NULL)
  		return -ENOSYS;
  
  	lx = &rtlx->channel[index];

  	mutex_lock(&channel_wqs[index].mutex);

  	smp_rmb();
  	lx_write = lx->lx_write;

  	/* find out how much in total */

  	count = min(count,

  		     (size_t)(lx_write + lx->buffer_size - lx->lx_read)

  		     % lx->buffer_size);

  
  	/* then how much from the read pointer onwards */

  	fl = min(count, (size_t)lx->buffer_size - lx->lx_read);

  	failed = copy_to_user(buff, lx->lx_buffer + lx->lx_read, fl);
  	if (failed)
  		goto out;

  
  	/* and if there is anything left at the beginning of the buffer */

  	if (count - fl)

  		failed = copy_to_user(buff + fl, lx->lx_buffer, count - fl);
  
  out:
  	count -= failed;

  	smp_wmb();
  	lx->lx_read = (lx->lx_read + count) % lx->buffer_size;
  	smp_wmb();

  	mutex_unlock(&channel_wqs[index].mutex);

  	return count;

  }

  ssize_t rtlx_write(int index, const void __user *buffer, size_t count)

  {
  	struct rtlx_channel *rt;

  	unsigned long failed;

  	size_t rt_read;

  	size_t fl;
  
  	if (rtlx == NULL)
  		return(-ENOSYS);
  
  	rt = &rtlx->channel[index];

  	mutex_lock(&channel_wqs[index].mutex);

  	smp_rmb();
  	rt_read = rt->rt_read;

  	/* total number of bytes to copy */

  	count = min(count, (size_t)write_spacefree(rt_read, rt->rt_write,
  							rt->buffer_size));

  
  	/* first bit from write pointer to the end of the buffer, or count */
  	fl = min(count, (size_t) rt->buffer_size - rt->rt_write);

  	failed = copy_from_user(rt->rt_buffer + rt->rt_write, buffer, fl);
  	if (failed)
  		goto out;

  
  	/* if there's any left copy to the beginning of the buffer */

  	if (count - fl) {
  		failed = copy_from_user(rt->rt_buffer, buffer + fl, count - fl);
  	}
  
  out:

  	count -= failed;

  	smp_wmb();
  	rt->rt_write = (rt->rt_write + count) % rt->buffer_size;
  	smp_wmb();

  	mutex_unlock(&channel_wqs[index].mutex);

  	return count;

  }
  
  
  static int file_open(struct inode *inode, struct file *filp)
  {

  	return rtlx_open(iminor(inode), (filp->f_flags & O_NONBLOCK) ? 0 : 1);

  }
  
  static int file_release(struct inode *inode, struct file *filp)
  {

  	return rtlx_release(iminor(inode));

  }
  
  static unsigned int file_poll(struct file *file, poll_table * wait)
  {
  	int minor;
  	unsigned int mask = 0;

  	minor = iminor(file->f_path.dentry->d_inode);

  
  	poll_wait(file, &channel_wqs[minor].rt_queue, wait);
  	poll_wait(file, &channel_wqs[minor].lx_queue, wait);
  
  	if (rtlx == NULL)
  		return 0;
  
  	/* data available to read? */
  	if (rtlx_read_poll(minor, 0))
  		mask |= POLLIN | POLLRDNORM;
  
  	/* space to write */
  	if (rtlx_write_poll(minor))
  		mask |= POLLOUT | POLLWRNORM;
  
  	return mask;
  }
  
  static ssize_t file_read(struct file *file, char __user * buffer, size_t count,
  			 loff_t * ppos)
  {

  	int minor = iminor(file->f_path.dentry->d_inode);

  
  	/* data available? */
  	if (!rtlx_read_poll(minor, (file->f_flags & O_NONBLOCK) ? 0 : 1)) {
  		return 0;	// -EAGAIN makes cat whinge
  	}

  	return rtlx_read(minor, buffer, count);

  }
  
  static ssize_t file_write(struct file *file, const char __user * buffer,

  			  size_t count, loff_t * ppos)
  {
  	int minor;
  	struct rtlx_channel *rt;

  	minor = iminor(file->f_path.dentry->d_inode);

  	rt = &rtlx->channel[minor];
  
  	/* any space left... */

  	if (!rtlx_write_poll(minor)) {

  		int ret = 0;

  
  		if (file->f_flags & O_NONBLOCK)

  			return -EAGAIN;

  		__wait_event_interruptible(channel_wqs[minor].rt_queue,
  		                           rtlx_write_poll(minor),
  		                           ret);
  		if (ret)
  			return ret;

  	}

  	return rtlx_write(minor, buffer, count);

  }

  static const struct file_operations rtlx_fops = {

  	.owner =   THIS_MODULE,
  	.open =    file_open,
  	.release = file_release,
  	.write =   file_write,
  	.read =    file_read,

  	.poll =    file_poll,
  	.llseek =  noop_llseek,

  };

  static struct irqaction rtlx_irq = {
  	.handler	= rtlx_interrupt,

  	.name		= "RTLX",
  };

  static int rtlx_irq_num = MIPS_CPU_IRQ_BASE + MIPS_CPU_RTLX_IRQ;

  static char register_chrdev_failed[] __initdata =
  	KERN_ERR "rtlx_module_init: unable to register device
  ";

  static int __init rtlx_module_init(void)

  {

  	struct device *dev;
  	int i, err;

  	if (!cpu_has_mipsmt) {
  		printk("VPE loader: not a MIPS MT capable processor
  ");
  		return -ENODEV;
  	}
  
  	if (tclimit == 0) {
  		printk(KERN_WARNING "No TCs reserved for AP/SP, not "
  		       "initializing RTLX.
  Pass maxtcs=<n> argument as kernel "
  		       "argument
  ");
  
  		return -ENODEV;
  	}

  	major = register_chrdev(0, module_name, &rtlx_fops);
  	if (major < 0) {
  		printk(register_chrdev_failed);
  		return major;

  	}

  	/* initialise the wait queues */
  	for (i = 0; i < RTLX_CHANNELS; i++) {
  		init_waitqueue_head(&channel_wqs[i].rt_queue);
  		init_waitqueue_head(&channel_wqs[i].lx_queue);

  		atomic_set(&channel_wqs[i].in_open, 0);

  		mutex_init(&channel_wqs[i].mutex);

  		dev = device_create(mt_class, NULL, MKDEV(major, i), NULL,
  				    "%s%d", module_name, i);

  		if (IS_ERR(dev)) {
  			err = PTR_ERR(dev);
  			goto out_chrdev;
  		}

  	}
  
  	/* set up notifiers */
  	notify.start = starting;
  	notify.stop = stopping;

  	vpe_notify(tclimit, &notify);

  
  	if (cpu_has_vint)
  		set_vi_handler(MIPS_CPU_RTLX_IRQ, rtlx_dispatch);

  	else {
  		pr_err("APRP RTLX init on non-vectored-interrupt processor
  ");
  		err = -ENODEV;
  		goto out_chrdev;
  	}

  
  	rtlx_irq.dev_id = rtlx;
  	setup_irq(rtlx_irq_num, &rtlx_irq);

  	return 0;

  
  out_chrdev:
  	for (i = 0; i < RTLX_CHANNELS; i++)
  		device_destroy(mt_class, MKDEV(major, i));
  
  	return err;

  }

  static void __exit rtlx_module_exit(void)

  {

  	int i;
  
  	for (i = 0; i < RTLX_CHANNELS; i++)
  		device_destroy(mt_class, MKDEV(major, i));

  	unregister_chrdev(major, module_name);
  }
  
  module_init(rtlx_module_init);
  module_exit(rtlx_module_exit);

  MODULE_DESCRIPTION("MIPS RTLX");

  MODULE_AUTHOR("Elizabeth Oldham, MIPS Technologies, Inc.");

  MODULE_LICENSE("GPL");