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/smp_lock.h>
  21 #include <linux/miscdevice.h>
  22 #include <linux/proc_fs.h>
  23 #include <linux/hdpu_features.h>
  24 #include <linux/platform_device.h>
  25 #include <asm/uaccess.h>
  26 #include <linux/seq_file.h>
  27 #include <asm/io.h>
  28
  29 #define SKY_CPUSTATE_VERSION            "1.1"
  30
  31 static int hdpu_cpustate_probe(struct platform_device *pdev);
  32 static int hdpu_cpustate_remove(struct platform_device *pdev);
  33
  34 static unsigned char cpustate_get_state(void);
  35 static int cpustate_proc_open(struct inode *inode, struct file *file);
  36 static int cpustate_proc_read(struct seq_file *seq, void *offset);
  37
  38 static struct cpustate_t cpustate;
  39
  40 static const struct file_operations proc_cpustate = {
  41         .open = cpustate_proc_open,
  42         .read = seq_read,
  43         .llseek = seq_lseek,
  44         .release = single_release,
  45         .owner = THIS_MODULE,
  46 };
  47
  48 static int cpustate_proc_open(struct inode *inode, struct file *file)
  49 {
  50         return single_open(file, cpustate_proc_read, NULL);
  51 }
  52
  53 static int cpustate_proc_read(struct seq_file *seq, void *offset)
  54 {
  55         seq_printf(seq, "CPU State: %04x\n", cpustate_get_state());
  56         return 0;
  57 }
  58
  59 static int cpustate_get_ref(int excl)
  60 {
  61
  62         int retval = -EBUSY;
  63
  64         spin_lock(&cpustate.lock);
  65
  66         if (cpustate.excl)
  67                 goto out_busy;
  68
  69         if (excl) {
  70                 if (cpustate.open_count)
  71                         goto out_busy;
  72                 cpustate.excl = 1;
  73         }
  74
  75         cpustate.open_count++;
  76         retval = 0;
  77
  78       out_busy:
  79         spin_unlock(&cpustate.lock);
  80         return retval;
  81 }
  82
  83 static int cpustate_free_ref(void)
  84 {
  85
  86         spin_lock(&cpustate.lock);
  87
  88         cpustate.excl = 0;
  89         cpustate.open_count--;
  90
  91         spin_unlock(&cpustate.lock);
  92         return 0;
  93 }
  94
  95 static unsigned char cpustate_get_state(void)
  96 {
  97
  98         return cpustate.cached_val;
  99 }
 100
 101 static void cpustate_set_state(unsigned char new_state)
 102 {
 103         unsigned int state = (new_state << 21);
 104
 105 #ifdef DEBUG_CPUSTATE
 106         printk("CPUSTATE -> 0x%x\n", new_state);
 107 #endif
 108         spin_lock(&cpustate.lock);
 109         cpustate.cached_val = new_state;
 110         writel((0xff << 21), cpustate.clr_addr);
 111         writel(state, cpustate.set_addr);
 112         spin_unlock(&cpustate.lock);
 113 }
 114
 115 /*
 116  *      Now all the various file operations that we export.
 117  */
 118
 119 static ssize_t cpustate_read(struct file *file, char *buf,
 120                              size_t count, loff_t * ppos)
 121 {
 122         unsigned char data;
 123
 124         if (count == 0)
 125                 return 0;
 126
 127         data = cpustate_get_state();
 128         if (copy_to_user(buf, &data, sizeof(unsigned char)))
 129                 return -EFAULT;
 130         return sizeof(unsigned char);
 131 }
 132
 133 static ssize_t cpustate_write(struct file *file, const char *buf,
 134                               size_t count, loff_t * ppos)
 135 {
 136         unsigned char data;
 137
 138         if (count == 0)
 139                 return 0;
 140
 141         if (copy_from_user((unsigned char *)&data, buf, sizeof(unsigned char)))
 142                 return -EFAULT;
 143
 144         cpustate_set_state(data);
 145         return sizeof(unsigned char);
 146 }
 147
 148 static int cpustate_open(struct inode *inode, struct file *file)
 149 {
 150         int ret;
 151
 152         lock_kernel();
 153         ret = cpustate_get_ref((file->f_flags & O_EXCL));
 154         unlock_kernel();
 155
 156         return ret;
 157 }
 158
 159 static int cpustate_release(struct inode *inode, struct file *file)
 160 {
 161         return cpustate_free_ref();
 162 }
 163
 164 static struct platform_driver hdpu_cpustate_driver = {
 165         .probe = hdpu_cpustate_probe,
 166         .remove = hdpu_cpustate_remove,
 167         .driver = {
 168                 .name = HDPU_CPUSTATE_NAME,
 169                 .owner = THIS_MODULE,
 170         },
 171 };
 172
 173 /*
 174  *      The various file operations we support.
 175  */
 176 static const struct file_operations cpustate_fops = {
 177       .owner    = THIS_MODULE,
 178       .open     = cpustate_open,
 179       .release  = cpustate_release,
 180       .read     = cpustate_read,
 181       .write    = cpustate_write,
 182       .llseek   = no_llseek,
 183 };
 184
 185 static struct miscdevice cpustate_dev = {
 186         .minor  = MISC_DYNAMIC_MINOR,
 187         .name   = "sky_cpustate",
 188         .fops   = &cpustate_fops,
 189 };
 190
 191 static int hdpu_cpustate_probe(struct platform_device *pdev)
 192 {
 193         struct resource *res;
 194         struct proc_dir_entry *proc_de;
 195         int ret;
 196
 197         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 198         if (!res) {
 199                 printk(KERN_ERR "sky_cpustate: "
 200                        "Invalid memory resource.\n");
 201                 return -EINVAL;
 202         }
 203         cpustate.set_addr = (unsigned long *)res->start;
 204         cpustate.clr_addr = (unsigned long *)res->end - 1;
 205
 206         ret = misc_register(&cpustate_dev);
 207         if (ret) {
 208                 printk(KERN_WARNING "sky_cpustate: "
 209                        "Unable to register misc device.\n");
 210                 cpustate.set_addr = NULL;
 211                 cpustate.clr_addr = NULL;
 212                 return ret;
 213         }
 214
 215         proc_de = proc_create("sky_cpustate", 0666, NULL, &proc_cpustate);
 216         if (!proc_de) {
 217                 printk(KERN_WARNING "sky_cpustate: "
 218                        "Unable to create proc entry\n");
 219         }
 220
 221         printk(KERN_INFO "Sky CPU State Driver v" SKY_CPUSTATE_VERSION "\n");
 222         return 0;
 223 }
 224
 225 static int hdpu_cpustate_remove(struct platform_device *pdev)
 226 {
 227         cpustate.set_addr = NULL;
 228         cpustate.clr_addr = NULL;
 229
 230         remove_proc_entry("sky_cpustate", NULL);
 231         misc_deregister(&cpustate_dev);
 232
 233         return 0;
 234 }
 235
 236 static int __init cpustate_init(void)
 237 {
 238         return platform_driver_register(&hdpu_cpustate_driver);
 239 }
 240
 241 static void __exit cpustate_exit(void)
 242 {
 243         platform_driver_unregister(&hdpu_cpustate_driver);
 244 }
 245
 246 module_init(cpustate_init);
 247 module_exit(cpustate_exit);
 248
 249 MODULE_AUTHOR("Brian Waite");
 250 MODULE_LICENSE("GPL");
 251 MODULE_ALIAS("platform:" HDPU_CPUSTATE_NAME);