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