/*
 *      Sky CPU State Driver
 *
 *      Copyright (C) 2002 Brian Waite
 *
 *      This driver allows use of the CPU state bits
 *      It exports the /dev/sky_cpustate and also
 *      /proc/sky_cpustate pseudo-file for status information.
 *
 *      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; either version
 *      2 of the License, or (at your option) any later version.
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/smp_lock.h>
#include <linux/miscdevice.h>
#include <linux/proc_fs.h>
#include <linux/hdpu_features.h>
#include <linux/platform_device.h>
#include <asm/uaccess.h>
#include <linux/seq_file.h>
#include <asm/io.h>

#define SKY_CPUSTATE_VERSION            "1.1"

static int hdpu_cpustate_probe(struct platform_device *pdev);
static int hdpu_cpustate_remove(struct platform_device *pdev);

static unsigned char cpustate_get_state(void);
static int cpustate_proc_open(struct inode *inode, struct file *file);
static int cpustate_proc_read(struct seq_file *seq, void *offset);

static struct cpustate_t cpustate;

static const struct file_operations proc_cpustate = {
        .open = cpustate_proc_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
        .owner = THIS_MODULE,
};

static int cpustate_proc_open(struct inode *inode, struct file *file)
{
        return single_open(file, cpustate_proc_read, NULL);
}

static int cpustate_proc_read(struct seq_file *seq, void *offset)
{
        seq_printf(seq, "CPU State: %04x\n", cpustate_get_state());
        return 0;
}

static int cpustate_get_ref(int excl)
{

        int retval = -EBUSY;

        spin_lock(&cpustate.lock);

        if (cpustate.excl)
                goto out_busy;

        if (excl) {
                if (cpustate.open_count)
                        goto out_busy;
                cpustate.excl = 1;
        }

        cpustate.open_count++;
        retval = 0;

      out_busy:
        spin_unlock(&cpustate.lock);
        return retval;
}

static int cpustate_free_ref(void)
{

        spin_lock(&cpustate.lock);

        cpustate.excl = 0;
        cpustate.open_count--;

        spin_unlock(&cpustate.lock);
        return 0;
}

static unsigned char cpustate_get_state(void)
{

        return cpustate.cached_val;
}

static void cpustate_set_state(unsigned char new_state)
{
        unsigned int state = (new_state << 21);

#ifdef DEBUG_CPUSTATE
        printk("CPUSTATE -> 0x%x\n", new_state);
#endif
        spin_lock(&cpustate.lock);
        cpustate.cached_val = new_state;
        writel((0xff << 21), cpustate.clr_addr);
        writel(state, cpustate.set_addr);
        spin_unlock(&cpustate.lock);
}

/*
 *      Now all the various file operations that we export.
 */

static ssize_t cpustate_read(struct file *file, char *buf,
                             size_t count, loff_t * ppos)
{
        unsigned char data;

        if (count < 0)
                return -EFAULT;
        if (count == 0)
                return 0;

        data = cpustate_get_state();
        if (copy_to_user(buf, &data, sizeof(unsigned char)))
                return -EFAULT;
        return sizeof(unsigned char);
}

static ssize_t cpustate_write(struct file *file, const char *buf,
                              size_t count, loff_t * ppos)
{
        unsigned char data;

        if (count < 0)
                return -EFAULT;

        if (count == 0)
                return 0;

        if (copy_from_user((unsigned char *)&data, buf, sizeof(unsigned char)))
                return -EFAULT;

        cpustate_set_state(data);
        return sizeof(unsigned char);
}

static int cpustate_open(struct inode *inode, struct file *file)
{
        int ret;

        lock_kernel();
        ret = cpustate_get_ref((file->f_flags & O_EXCL));
        unlock_kernel();

        return ret;
}

static int cpustate_release(struct inode *inode, struct file *file)
{
        return cpustate_free_ref();
}

static struct platform_driver hdpu_cpustate_driver = {
        .probe = hdpu_cpustate_probe,
        .remove = hdpu_cpustate_remove,
        .driver = {
                .name = HDPU_CPUSTATE_NAME,
                .owner = THIS_MODULE,
        },
};

/*
 *      The various file operations we support.
 */
static const struct file_operations cpustate_fops = {
      .owner    = THIS_MODULE,
      .open     = cpustate_open,
      .release  = cpustate_release,
      .read     = cpustate_read,
      .write    = cpustate_write,
      .llseek   = no_llseek,
};

static struct miscdevice cpustate_dev = {
        .minor  = MISC_DYNAMIC_MINOR,
        .name   = "sky_cpustate",
        .fops   = &cpustate_fops,
};

static int hdpu_cpustate_probe(struct platform_device *pdev)
{
        struct resource *res;
        struct proc_dir_entry *proc_de;
        int ret;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res) {
                printk(KERN_ERR "sky_cpustate: "
                       "Invalid memory resource.\n");
                return -EINVAL;
        }
        cpustate.set_addr = (unsigned long *)res->start;
        cpustate.clr_addr = (unsigned long *)res->end - 1;

        ret = misc_register(&cpustate_dev);
        if (ret) {
                printk(KERN_WARNING "sky_cpustate: "
                       "Unable to register misc device.\n");
                cpustate.set_addr = NULL;
                cpustate.clr_addr = NULL;
                return ret;
        }

        proc_de = proc_create("sky_cpustate", 0666, NULL, &proc_cpustate);
        if (!proc_de) {
                printk(KERN_WARNING "sky_cpustate: "
                       "Unable to create proc entry\n");
        }

        printk(KERN_INFO "Sky CPU State Driver v" SKY_CPUSTATE_VERSION "\n");
        return 0;
}

static int hdpu_cpustate_remove(struct platform_device *pdev)
{
        cpustate.set_addr = NULL;
        cpustate.clr_addr = NULL;

        remove_proc_entry("sky_cpustate", NULL);
        misc_deregister(&cpustate_dev);

        return 0;
}

static int __init cpustate_init(void)
{
        return platform_driver_register(&hdpu_cpustate_driver);
}

static void __exit cpustate_exit(void)
{
        platform_driver_unregister(&hdpu_cpustate_driver);
}

module_init(cpustate_init);
module_exit(cpustate_exit);

MODULE_AUTHOR("Brian Waite");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" HDPU_CPUSTATE_NAME);