drivers/misc/hdpuftrs/hdpu_cpustate.c

   1 /*
   2  *      Sky CPU State Driver
   3  *
   4  *      Copyright (C) 2002 Brian Waite
   5  *
   6  *      This driver allows use of the CPU state bits
   7  *      It exports the /dev/sky_cpustate and also
   8  *      /proc/sky_cpustate pseudo-file for status information.
   9  *
  10  *      This program is free software; you can redistribute it and/or
  11  *      modify it under the terms of the GNU General Public License
  12  *      as published by the Free Software Foundation; either version
  13  *      2 of the License, or (at your option) any later version.
  14  *
  15  */
  16
  17 #include <linux/module.h>
  18 #include <linux/kernel.h>
  19 #include <linux/spinlock.h>
  20 #include <linux/miscdevice.h>
  21 #include <linux/proc_fs.h>
  22 #include <linux/platform_device.h>
  23 #include <asm/uaccess.h>
  24 #include <linux/hdpu_features.h>
  25
  26 #define SKY_CPUSTATE_VERSION            "1.1"
  27
  28 static int hdpu_cpustate_probe(struct platform_device *pdev);
  29 static int hdpu_cpustate_remove(struct platform_device *pdev);
  30
  31 struct cpustate_t cpustate;
  32
  33 static int cpustate_get_ref(int excl)
  34 {
  35
  36         int retval = -EBUSY;
  37
  38         spin_lock(&cpustate.lock);
  39
  40         if (cpustate.excl)
  41                 goto out_busy;
  42
  43         if (excl) {
  44                 if (cpustate.open_count)
  45                         goto out_busy;
  46                 cpustate.excl = 1;
  47         }
  48
  49         cpustate.open_count++;
  50         retval = 0;
  51
  52       out_busy:
  53         spin_unlock(&cpustate.lock);
  54         return retval;
  55 }
  56
  57 static int cpustate_free_ref(void)
  58 {
  59
  60         spin_lock(&cpustate.lock);
  61
  62         cpustate.excl = 0;
  63         cpustate.open_count--;
  64
  65         spin_unlock(&cpustate.lock);
  66         return 0;
  67 }
  68
  69 unsigned char cpustate_get_state(void)
  70 {
  71
  72         return cpustate.cached_val;
  73 }
  74
  75 void cpustate_set_state(unsigned char new_state)
  76 {
  77         unsigned int state = (new_state << 21);
  78
  79 #ifdef DEBUG_CPUSTATE
  80         printk("CPUSTATE -> 0x%x\n", new_state);
  81 #endif
  82         spin_lock(&cpustate.lock);
  83         cpustate.cached_val = new_state;
  84         writel((0xff << 21), cpustate.clr_addr);
  85         writel(state, cpustate.set_addr);
  86         spin_unlock(&cpustate.lock);
  87 }
  88
  89 /*
  90  *      Now all the various file operations that we export.
  91  */
  92
  93 static ssize_t cpustate_read(struct file *file, char *buf,
  94                              size_t count, loff_t * ppos)
  95 {
  96         unsigned char data;
  97
  98         if (count < 0)
  99                 return -EFAULT;
 100         if (count == 0)
 101                 return 0;
 102
 103         data = cpustate_get_state();
 104         if (copy_to_user(buf, &data, sizeof(unsigned char)))
 105                 return -EFAULT;
 106         return sizeof(unsigned char);
 107 }
 108
 109 static ssize_t cpustate_write(struct file *file, const char *buf,
 110                               size_t count, loff_t * ppos)
 111 {
 112         unsigned char data;
 113
 114         if (count < 0)
 115                 return -EFAULT;
 116
 117         if (count == 0)
 118                 return 0;
 119
 120         if (copy_from_user((unsigned char *)&data, buf, sizeof(unsigned char)))
 121                 return -EFAULT;
 122
 123         cpustate_set_state(data);
 124         return sizeof(unsigned char);
 125 }
 126
 127 static int cpustate_open(struct inode *inode, struct file *file)
 128 {
 129         return cpustate_get_ref((file->f_flags & O_EXCL));
 130 }
 131
 132 static int cpustate_release(struct inode *inode, struct file *file)
 133 {
 134         return cpustate_free_ref();
 135 }
 136
 137 /*
 138  *      Info exported via "/proc/sky_cpustate".
 139  */
 140 static int cpustate_read_proc(char *page, char **start, off_t off,
 141                               int count, int *eof, void *data)
 142 {
 143         char *p = page;
 144         int len = 0;
 145
 146         p += sprintf(p, "CPU State: %04x\n", cpustate_get_state());
 147         len = p - page;
 148
 149         if (len <= off + count)
 150                 *eof = 1;
 151         *start = page + off;
 152         len -= off;
 153         if (len > count)
 154                 len = count;
 155         if (len < 0)
 156                 len = 0;
 157         return len;
 158 }
 159
 160 static struct platform_driver hdpu_cpustate_driver = {
 161         .probe = hdpu_cpustate_probe,
 162         .remove = hdpu_cpustate_remove,
 163         .driver = {
 164                 .name = HDPU_CPUSTATE_NAME,
 165         },
 166 };
 167
 168 /*
 169  *      The various file operations we support.
 170  */
 171 static const struct file_operations cpustate_fops = {
 172       owner:THIS_MODULE,
 173       open:cpustate_open,
 174       release:cpustate_release,
 175       read:cpustate_read,
 176       write:cpustate_write,
 177       fasync:NULL,
 178       poll:NULL,
 179       ioctl:NULL,
 180       llseek:no_llseek,
 181
 182 };
 183
 184 static struct miscdevice cpustate_dev = {
 185         MISC_DYNAMIC_MINOR,
 186         "sky_cpustate",
 187         &cpustate_fops
 188 };
 189
 190 static int hdpu_cpustate_probe(struct platform_device *pdev)
 191 {
 192         struct resource *res;
 193         struct proc_dir_entry *proc_de;
 194         int ret;
 195
 196         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 197         cpustate.set_addr = (unsigned long *)res->start;
 198         cpustate.clr_addr = (unsigned long *)res->end - 1;
 199
 200         ret = misc_register(&cpustate_dev);
 201         if (ret) {
 202                 printk(KERN_WARNING "sky_cpustate: Unable to register misc "
 203                                         "device.\n");
 204                 cpustate.set_addr = NULL;
 205                 cpustate.clr_addr = NULL;
 206                 return ret;
 207         }
 208
 209         proc_de = create_proc_read_entry("sky_cpustate", 0, 0,
 210                                         cpustate_read_proc, NULL);
 211         if (proc_de == NULL)
 212                 printk(KERN_WARNING "sky_cpustate: Unable to create proc "
 213                                         "dir entry\n");
 214
 215         printk(KERN_INFO "Sky CPU State Driver v" SKY_CPUSTATE_VERSION "\n");
 216         return 0;
 217 }
 218
 219 static int hdpu_cpustate_remove(struct platform_device *pdev)
 220 {
 221
 222         cpustate.set_addr = NULL;
 223         cpustate.clr_addr = NULL;
 224
 225         remove_proc_entry("sky_cpustate", NULL);
 226         misc_deregister(&cpustate_dev);
 227         return 0;
 228
 229 }
 230
 231 static int __init cpustate_init(void)
 232 {
 233         int rc;
 234         rc = platform_driver_register(&hdpu_cpustate_driver);
 235         return rc;
 236 }
 237
 238 static void __exit cpustate_exit(void)
 239 {
 240         platform_driver_unregister(&hdpu_cpustate_driver);
 241 }
 242
 243 module_init(cpustate_init);
 244 module_exit(cpustate_exit);
 245
 246 MODULE_AUTHOR("Brian Waite");
 247 MODULE_LICENSE("GPL");