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Linux/drivers/watchdog/gef_wdt.c

  1 /*
  2  * GE watchdog userspace interface
  3  *
  4  * Author:  Martyn Welch <martyn.welch@ge.com>
  5  *
  6  * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
  7  *
  8  * This program is free software; you can redistribute  it and/or modify it
  9  * under  the terms of  the GNU General  Public License as published by the
 10  * Free Software Foundation;  either version 2 of the  License, or (at your
 11  * option) any later version.
 12  *
 13  * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
 14  *   Author: James Chapman <jchapman@katalix.com>
 15  */
 16 
 17 /* TODO:
 18  * This driver does not provide support for the hardwares capability of sending
 19  * an interrupt at a programmable threshold.
 20  *
 21  * This driver currently can only support 1 watchdog - there are 2 in the
 22  * hardware that this driver supports. Thus one could be configured as a
 23  * process-based watchdog (via /dev/watchdog), the second (using the interrupt
 24  * capabilities) a kernel-based watchdog.
 25  */
 26 
 27 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 28 
 29 #include <linux/kernel.h>
 30 #include <linux/compiler.h>
 31 #include <linux/init.h>
 32 #include <linux/module.h>
 33 #include <linux/miscdevice.h>
 34 #include <linux/watchdog.h>
 35 #include <linux/fs.h>
 36 #include <linux/of.h>
 37 #include <linux/of_address.h>
 38 #include <linux/of_platform.h>
 39 #include <linux/io.h>
 40 #include <linux/uaccess.h>
 41 
 42 #include <sysdev/fsl_soc.h>
 43 
 44 /*
 45  * The watchdog configuration register contains a pair of 2-bit fields,
 46  *   1.  a reload field, bits 27-26, which triggers a reload of
 47  *       the countdown register, and
 48  *   2.  an enable field, bits 25-24, which toggles between
 49  *       enabling and disabling the watchdog timer.
 50  * Bit 31 is a read-only field which indicates whether the
 51  * watchdog timer is currently enabled.
 52  *
 53  * The low 24 bits contain the timer reload value.
 54  */
 55 #define GEF_WDC_ENABLE_SHIFT    24
 56 #define GEF_WDC_SERVICE_SHIFT   26
 57 #define GEF_WDC_ENABLED_SHIFT   31
 58 
 59 #define GEF_WDC_ENABLED_TRUE    1
 60 #define GEF_WDC_ENABLED_FALSE   0
 61 
 62 /* Flags bits */
 63 #define GEF_WDOG_FLAG_OPENED    0
 64 
 65 static unsigned long wdt_flags;
 66 static int wdt_status;
 67 static void __iomem *gef_wdt_regs;
 68 static int gef_wdt_timeout;
 69 static int gef_wdt_count;
 70 static unsigned int bus_clk;
 71 static char expect_close;
 72 static DEFINE_SPINLOCK(gef_wdt_spinlock);
 73 
 74 static bool nowayout = WATCHDOG_NOWAYOUT;
 75 module_param(nowayout, bool, 0);
 76 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
 77         __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 78 
 79 
 80 static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
 81 {
 82         u32 data;
 83         u32 enabled;
 84         int ret = 0;
 85 
 86         spin_lock(&gef_wdt_spinlock);
 87         data = ioread32be(gef_wdt_regs);
 88         enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
 89 
 90         /* only toggle the requested field if enabled state matches predicate */
 91         if ((enabled ^ enabled_predicate) == 0) {
 92                 /* We write a 1, then a 2 -- to the appropriate field */
 93                 data = (1 << field_shift) | gef_wdt_count;
 94                 iowrite32be(data, gef_wdt_regs);
 95 
 96                 data = (2 << field_shift) | gef_wdt_count;
 97                 iowrite32be(data, gef_wdt_regs);
 98                 ret = 1;
 99         }
100         spin_unlock(&gef_wdt_spinlock);
101 
102         return ret;
103 }
104 
105 static void gef_wdt_service(void)
106 {
107         gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
108                 GEF_WDC_SERVICE_SHIFT);
109 }
110 
111 static void gef_wdt_handler_enable(void)
112 {
113         if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
114                                    GEF_WDC_ENABLE_SHIFT)) {
115                 gef_wdt_service();
116                 pr_notice("watchdog activated\n");
117         }
118 }
119 
120 static void gef_wdt_handler_disable(void)
121 {
122         if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
123                                    GEF_WDC_ENABLE_SHIFT))
124                 pr_notice("watchdog deactivated\n");
125 }
126 
127 static void gef_wdt_set_timeout(unsigned int timeout)
128 {
129         /* maximum bus cycle count is 0xFFFFFFFF */
130         if (timeout > 0xFFFFFFFF / bus_clk)
131                 timeout = 0xFFFFFFFF / bus_clk;
132 
133         /* Register only holds upper 24 bits, bit shifted into lower 24 */
134         gef_wdt_count = (timeout * bus_clk) >> 8;
135         gef_wdt_timeout = timeout;
136 }
137 
138 
139 static ssize_t gef_wdt_write(struct file *file, const char __user *data,
140                                  size_t len, loff_t *ppos)
141 {
142         if (len) {
143                 if (!nowayout) {
144                         size_t i;
145 
146                         expect_close = 0;
147 
148                         for (i = 0; i != len; i++) {
149                                 char c;
150                                 if (get_user(c, data + i))
151                                         return -EFAULT;
152                                 if (c == 'V')
153                                         expect_close = 42;
154                         }
155                 }
156                 gef_wdt_service();
157         }
158 
159         return len;
160 }
161 
162 static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
163                                                         unsigned long arg)
164 {
165         int timeout;
166         int options;
167         void __user *argp = (void __user *)arg;
168         static const struct watchdog_info info = {
169                 .options =      WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
170                                 WDIOF_KEEPALIVEPING,
171                 .firmware_version = 0,
172                 .identity = "GE watchdog",
173         };
174 
175         switch (cmd) {
176         case WDIOC_GETSUPPORT:
177                 if (copy_to_user(argp, &info, sizeof(info)))
178                         return -EFAULT;
179                 break;
180 
181         case WDIOC_GETSTATUS:
182         case WDIOC_GETBOOTSTATUS:
183                 if (put_user(wdt_status, (int __user *)argp))
184                         return -EFAULT;
185                 wdt_status &= ~WDIOF_KEEPALIVEPING;
186                 break;
187 
188         case WDIOC_SETOPTIONS:
189                 if (get_user(options, (int __user *)argp))
190                         return -EFAULT;
191 
192                 if (options & WDIOS_DISABLECARD)
193                         gef_wdt_handler_disable();
194 
195                 if (options & WDIOS_ENABLECARD)
196                         gef_wdt_handler_enable();
197                 break;
198 
199         case WDIOC_KEEPALIVE:
200                 gef_wdt_service();
201                 wdt_status |= WDIOF_KEEPALIVEPING;
202                 break;
203 
204         case WDIOC_SETTIMEOUT:
205                 if (get_user(timeout, (int __user *)argp))
206                         return -EFAULT;
207                 gef_wdt_set_timeout(timeout);
208                 /* Fall through */
209 
210         case WDIOC_GETTIMEOUT:
211                 if (put_user(gef_wdt_timeout, (int __user *)argp))
212                         return -EFAULT;
213                 break;
214 
215         default:
216                 return -ENOTTY;
217         }
218 
219         return 0;
220 }
221 
222 static int gef_wdt_open(struct inode *inode, struct file *file)
223 {
224         if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
225                 return -EBUSY;
226 
227         if (nowayout)
228                 __module_get(THIS_MODULE);
229 
230         gef_wdt_handler_enable();
231 
232         return nonseekable_open(inode, file);
233 }
234 
235 static int gef_wdt_release(struct inode *inode, struct file *file)
236 {
237         if (expect_close == 42)
238                 gef_wdt_handler_disable();
239         else {
240                 pr_crit("unexpected close, not stopping timer!\n");
241                 gef_wdt_service();
242         }
243         expect_close = 0;
244 
245         clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
246 
247         return 0;
248 }
249 
250 static const struct file_operations gef_wdt_fops = {
251         .owner = THIS_MODULE,
252         .llseek = no_llseek,
253         .write = gef_wdt_write,
254         .unlocked_ioctl = gef_wdt_ioctl,
255         .open = gef_wdt_open,
256         .release = gef_wdt_release,
257 };
258 
259 static struct miscdevice gef_wdt_miscdev = {
260         .minor = WATCHDOG_MINOR,
261         .name = "watchdog",
262         .fops = &gef_wdt_fops,
263 };
264 
265 
266 static int gef_wdt_probe(struct platform_device *dev)
267 {
268         int timeout = 10;
269         u32 freq;
270 
271         bus_clk = 133; /* in MHz */
272 
273         freq = fsl_get_sys_freq();
274         if (freq != -1)
275                 bus_clk = freq;
276 
277         /* Map devices registers into memory */
278         gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
279         if (gef_wdt_regs == NULL)
280                 return -ENOMEM;
281 
282         gef_wdt_set_timeout(timeout);
283 
284         gef_wdt_handler_disable();      /* in case timer was already running */
285 
286         return misc_register(&gef_wdt_miscdev);
287 }
288 
289 static int gef_wdt_remove(struct platform_device *dev)
290 {
291         misc_deregister(&gef_wdt_miscdev);
292 
293         gef_wdt_handler_disable();
294 
295         iounmap(gef_wdt_regs);
296 
297         return 0;
298 }
299 
300 static const struct of_device_id gef_wdt_ids[] = {
301         {
302                 .compatible = "gef,fpga-wdt",
303         },
304         {},
305 };
306 
307 static struct platform_driver gef_wdt_driver = {
308         .driver = {
309                 .name = "gef_wdt",
310                 .owner = THIS_MODULE,
311                 .of_match_table = gef_wdt_ids,
312         },
313         .probe          = gef_wdt_probe,
314         .remove         = gef_wdt_remove,
315 };
316 
317 static int __init gef_wdt_init(void)
318 {
319         pr_info("GE watchdog driver\n");
320         return platform_driver_register(&gef_wdt_driver);
321 }
322 
323 static void __exit gef_wdt_exit(void)
324 {
325         platform_driver_unregister(&gef_wdt_driver);
326 }
327 
328 module_init(gef_wdt_init);
329 module_exit(gef_wdt_exit);
330 
331 MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
332 MODULE_DESCRIPTION("GE watchdog driver");
333 MODULE_LICENSE("GPL");
334 MODULE_ALIAS("platform:gef_wdt");
335 

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