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 int ret;
36
37 ret = kstrtoul(buf, 10, &level);
38 if (ret != 0)
39 return ret;
40
41 /*
42 * Minimal acceptable IRQ levels are in the 2 - 16 range, but
43 * these are chomped so as to not interfere with normal IRQs.
44 *
45 * Level 1 is a special case on some CPUs in that it's not
46 * directly settable, but given that USERIMASK cuts off below a
47 * certain level, we don't care about this limitation here.
48 * Level 0 on the other hand equates to user masking disabled.
49 *
50 * We use the default priority level as a cut off so that only
51 * special case opt-in IRQs can be mangled.
52 */
53 if (level >= intc_get_dfl_prio_level())
54 return -EINVAL;
55
56 __raw_writel(0xa5 << 24 | level << 4, uimask);
57
58 return count;
59 }
60
61 static DEVICE_ATTR(userimask, S_IRUSR | S_IWUSR,
62 show_intc_userimask, store_intc_userimask);
63
64
userimask_sysdev_init(void)65 static int __init userimask_sysdev_init(void)
66 {
67 struct device *dev_root;
68 int ret = 0;
69
70 if (unlikely(!uimask))
71 return -ENXIO;
72
73 dev_root = bus_get_dev_root(&intc_subsys);
74 if (dev_root) {
75 ret = device_create_file(dev_root, &dev_attr_userimask);
76 put_device(dev_root);
77 }
78 return ret;
79 }
80 late_initcall(userimask_sysdev_init);
81
register_intc_userimask(unsigned long addr)82 int register_intc_userimask(unsigned long addr)
83 {
84 if (unlikely(uimask))
85 return -EBUSY;
86
87 uimask = ioremap(addr, SZ_4K);
88 if (unlikely(!uimask))
89 return -ENOMEM;
90
91 pr_info("userimask support registered for levels 0 -> %d\n",
92 intc_get_dfl_prio_level() - 1);
93
94 return 0;
95 }
96