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rtlx.c

/*
 * 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/module.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/elf.h>
#include <linux/seq_file.h>
#include <linux/smp_lock.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 <asm/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";

00052 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\n", 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\n",
                   chan->rt_state, chan->lx_state, chan->buffer_size);

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

            printk(" lx_read %d lx_write %d\n",
                   chan->lx_read, chan->lx_write);

            printk(" rt_buffer <%s>\n", chan->rt_buffer);
            printk(" lx_buffer <%s>\n", 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\n",
                  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\n");
            return -ENOSYS;
      }

      if (atomic_inc_return(&channel_wqs[index].in_open) > 1) {
            printk(KERN_DEBUG "rtlx_open channel %d already opened\n",
                   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\n");
                  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?\n");
                        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\n",
                         (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\n");
            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
};

static struct irqaction rtlx_irq = {
      .handler    = rtlx_interrupt,
      .flags            = IRQF_DISABLED,
      .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\n";

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\n");
            return -ENODEV;
      }

      if (tclimit == 0) {
            printk(KERN_WARNING "No TCs reserved for AP/SP, not "
                   "initializing RTLX.\nPass maxtcs=<n> argument as kernel "
                   "argument\n");

            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\n");
            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");

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