xref: /openbmc/linux/drivers/char/uv_mmtimer.c (revision b6dcefde)
1 /*
2  * Timer device implementation for SGI UV platform.
3  *
4  * This file is subject to the terms and conditions of the GNU General Public
5  * License.  See the file "COPYING" in the main directory of this archive
6  * for more details.
7  *
8  * Copyright (c) 2009 Silicon Graphics, Inc.  All rights reserved.
9  *
10  */
11 
12 #include <linux/types.h>
13 #include <linux/kernel.h>
14 #include <linux/ioctl.h>
15 #include <linux/module.h>
16 #include <linux/init.h>
17 #include <linux/errno.h>
18 #include <linux/mm.h>
19 #include <linux/fs.h>
20 #include <linux/mmtimer.h>
21 #include <linux/miscdevice.h>
22 #include <linux/posix-timers.h>
23 #include <linux/interrupt.h>
24 #include <linux/time.h>
25 #include <linux/math64.h>
26 #include <linux/smp_lock.h>
27 
28 #include <asm/genapic.h>
29 #include <asm/uv/uv_hub.h>
30 #include <asm/uv/bios.h>
31 #include <asm/uv/uv.h>
32 
33 MODULE_AUTHOR("Dimitri Sivanich <sivanich@sgi.com>");
34 MODULE_DESCRIPTION("SGI UV Memory Mapped RTC Timer");
35 MODULE_LICENSE("GPL");
36 
37 /* name of the device, usually in /dev */
38 #define UV_MMTIMER_NAME "mmtimer"
39 #define UV_MMTIMER_DESC "SGI UV Memory Mapped RTC Timer"
40 #define UV_MMTIMER_VERSION "1.0"
41 
42 static long uv_mmtimer_ioctl(struct file *file, unsigned int cmd,
43 						unsigned long arg);
44 static int uv_mmtimer_mmap(struct file *file, struct vm_area_struct *vma);
45 
46 /*
47  * Period in femtoseconds (10^-15 s)
48  */
49 static unsigned long uv_mmtimer_femtoperiod;
50 
51 static const struct file_operations uv_mmtimer_fops = {
52 	.owner = THIS_MODULE,
53 	.mmap =	uv_mmtimer_mmap,
54 	.unlocked_ioctl = uv_mmtimer_ioctl,
55 };
56 
57 /**
58  * uv_mmtimer_ioctl - ioctl interface for /dev/uv_mmtimer
59  * @file: file structure for the device
60  * @cmd: command to execute
61  * @arg: optional argument to command
62  *
63  * Executes the command specified by @cmd.  Returns 0 for success, < 0 for
64  * failure.
65  *
66  * Valid commands:
67  *
68  * %MMTIMER_GETOFFSET - Should return the offset (relative to the start
69  * of the page where the registers are mapped) for the counter in question.
70  *
71  * %MMTIMER_GETRES - Returns the resolution of the clock in femto (10^-15)
72  * seconds
73  *
74  * %MMTIMER_GETFREQ - Copies the frequency of the clock in Hz to the address
75  * specified by @arg
76  *
77  * %MMTIMER_GETBITS - Returns the number of bits in the clock's counter
78  *
79  * %MMTIMER_MMAPAVAIL - Returns 1 if registers can be mmap'd into userspace
80  *
81  * %MMTIMER_GETCOUNTER - Gets the current value in the counter and places it
82  * in the address specified by @arg.
83  */
84 static long uv_mmtimer_ioctl(struct file *file, unsigned int cmd,
85 						unsigned long arg)
86 {
87 	int ret = 0;
88 
89 	switch (cmd) {
90 	case MMTIMER_GETOFFSET:	/* offset of the counter */
91 		/*
92 		 * Starting with HUB rev 2.0, the UV RTC register is
93 		 * replicated across all cachelines of it's own page.
94 		 * This allows faster simultaneous reads from a given socket.
95 		 *
96 		 * The offset returned is in 64 bit units.
97 		 */
98 		if (uv_get_min_hub_revision_id() == 1)
99 			ret = 0;
100 		else
101 			ret = ((uv_blade_processor_id() * L1_CACHE_BYTES) %
102 					PAGE_SIZE) / 8;
103 		break;
104 
105 	case MMTIMER_GETRES: /* resolution of the clock in 10^-15 s */
106 		if (copy_to_user((unsigned long __user *)arg,
107 				&uv_mmtimer_femtoperiod, sizeof(unsigned long)))
108 			ret = -EFAULT;
109 		break;
110 
111 	case MMTIMER_GETFREQ: /* frequency in Hz */
112 		if (copy_to_user((unsigned long __user *)arg,
113 				&sn_rtc_cycles_per_second,
114 				sizeof(unsigned long)))
115 			ret = -EFAULT;
116 		break;
117 
118 	case MMTIMER_GETBITS: /* number of bits in the clock */
119 		ret = hweight64(UVH_RTC_REAL_TIME_CLOCK_MASK);
120 		break;
121 
122 	case MMTIMER_MMAPAVAIL:
123 		ret = 1;
124 		break;
125 
126 	case MMTIMER_GETCOUNTER:
127 		if (copy_to_user((unsigned long __user *)arg,
128 				(unsigned long *)uv_local_mmr_address(UVH_RTC),
129 				sizeof(unsigned long)))
130 			ret = -EFAULT;
131 		break;
132 	default:
133 		ret = -ENOTTY;
134 		break;
135 	}
136 	return ret;
137 }
138 
139 /**
140  * uv_mmtimer_mmap - maps the clock's registers into userspace
141  * @file: file structure for the device
142  * @vma: VMA to map the registers into
143  *
144  * Calls remap_pfn_range() to map the clock's registers into
145  * the calling process' address space.
146  */
147 static int uv_mmtimer_mmap(struct file *file, struct vm_area_struct *vma)
148 {
149 	unsigned long uv_mmtimer_addr;
150 
151 	if (vma->vm_end - vma->vm_start != PAGE_SIZE)
152 		return -EINVAL;
153 
154 	if (vma->vm_flags & VM_WRITE)
155 		return -EPERM;
156 
157 	if (PAGE_SIZE > (1 << 16))
158 		return -ENOSYS;
159 
160 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
161 
162 	uv_mmtimer_addr = UV_LOCAL_MMR_BASE | UVH_RTC;
163 	uv_mmtimer_addr &= ~(PAGE_SIZE - 1);
164 	uv_mmtimer_addr &= 0xfffffffffffffffUL;
165 
166 	if (remap_pfn_range(vma, vma->vm_start, uv_mmtimer_addr >> PAGE_SHIFT,
167 					PAGE_SIZE, vma->vm_page_prot)) {
168 		printk(KERN_ERR "remap_pfn_range failed in uv_mmtimer_mmap\n");
169 		return -EAGAIN;
170 	}
171 
172 	return 0;
173 }
174 
175 static struct miscdevice uv_mmtimer_miscdev = {
176 	MISC_DYNAMIC_MINOR,
177 	UV_MMTIMER_NAME,
178 	&uv_mmtimer_fops
179 };
180 
181 
182 /**
183  * uv_mmtimer_init - device initialization routine
184  *
185  * Does initial setup for the uv_mmtimer device.
186  */
187 static int __init uv_mmtimer_init(void)
188 {
189 	if (!is_uv_system()) {
190 		printk(KERN_ERR "%s: Hardware unsupported\n", UV_MMTIMER_NAME);
191 		return -1;
192 	}
193 
194 	/*
195 	 * Sanity check the cycles/sec variable
196 	 */
197 	if (sn_rtc_cycles_per_second < 100000) {
198 		printk(KERN_ERR "%s: unable to determine clock frequency\n",
199 		       UV_MMTIMER_NAME);
200 		return -1;
201 	}
202 
203 	uv_mmtimer_femtoperiod = ((unsigned long)1E15 +
204 				sn_rtc_cycles_per_second / 2) /
205 				sn_rtc_cycles_per_second;
206 
207 	if (misc_register(&uv_mmtimer_miscdev)) {
208 		printk(KERN_ERR "%s: failed to register device\n",
209 		       UV_MMTIMER_NAME);
210 		return -1;
211 	}
212 
213 	printk(KERN_INFO "%s: v%s, %ld MHz\n", UV_MMTIMER_DESC,
214 		UV_MMTIMER_VERSION,
215 		sn_rtc_cycles_per_second/(unsigned long)1E6);
216 
217 	return 0;
218 }
219 
220 module_init(uv_mmtimer_init);
221