1 /*
2 * Support for hardware-assisted userspace interrupt masking.
3 *
4 * Copyright (C) 2010 Paul Mundt
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License. See the file "COPYING" in the main directory of this archive
8 * for more details.
9 */
10 #define pr_fmt(fmt) "intc: " fmt
11
12 #include <linux/errno.h>
13 #include <linux/device.h>
14 #include <linux/init.h>
15 #include <linux/io.h>
16 #include <linux/stat.h>
17 #include <linux/sizes.h>
18 #include "internals.h"
19
20 static void __iomem *uimask;
21
22 static ssize_t
show_intc_userimask(struct device * dev,struct device_attribute * attr,char * buf)23 show_intc_userimask(struct device *dev,
24 struct device_attribute *attr, char *buf)
25 {
26 return sprintf(buf, "%d\n", (__raw_readl(uimask) >> 4) & 0xf);
27 }
28
29 static ssize_t
store_intc_userimask(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)30 store_intc_userimask(struct device *dev,
31 struct device_attribute *attr,
32 const char *buf, size_t count)
33 {
34 unsigned long level;
35
36 level = simple_strtoul(buf, NULL, 10);
37
38 /*
39 * Minimal acceptable IRQ levels are in the 2 - 16 range, but
40 * these are chomped so as to not interfere with normal IRQs.
41 *
42 * Level 1 is a special case on some CPUs in that it's not
43 * directly settable, but given that USERIMASK cuts off below a
44 * certain level, we don't care about this limitation here.
45 * Level 0 on the other hand equates to user masking disabled.
46 *
47 * We use the default priority level as a cut off so that only
48 * special case opt-in IRQs can be mangled.
49 */
50 if (level >= intc_get_dfl_prio_level())
51 return -EINVAL;
52
53 __raw_writel(0xa5 << 24 | level << 4, uimask);
54
55 return count;
56 }
57
58 static DEVICE_ATTR(userimask, S_IRUSR | S_IWUSR,
59 show_intc_userimask, store_intc_userimask);
60
61
userimask_sysdev_init(void)62 static int __init userimask_sysdev_init(void)
63 {
64 struct device *dev_root;
65 int ret = 0;
66
67 if (unlikely(!uimask))
68 return -ENXIO;
69
70 dev_root = bus_get_dev_root(&intc_subsys);
71 if (dev_root) {
72 ret = device_create_file(dev_root, &dev_attr_userimask);
73 put_device(dev_root);
74 }
75 return ret;
76 }
77 late_initcall(userimask_sysdev_init);
78
register_intc_userimask(unsigned long addr)79 int register_intc_userimask(unsigned long addr)
80 {
81 if (unlikely(uimask))
82 return -EBUSY;
83
84 uimask = ioremap(addr, SZ_4K);
85 if (unlikely(!uimask))
86 return -ENOMEM;
87
88 pr_info("userimask support registered for levels 0 -> %d\n",
89 intc_get_dfl_prio_level() - 1);
90
91 return 0;
92 }
93