rtlx.c

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/*
 * Copyright (C) 2005 MIPS Technologies, Inc.  All rights reserved.
 * Copyright (C) 2005, 06 Ralf Baechle ([email protected])
 *
 *  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/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\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,
    .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\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");