userimask.c

 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
20static void __iomem *uimask;
21
22static ssize_t
23show_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
29static ssize_t
30store_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
61static DEVICE_ATTR(userimask, S_IRUSR | S_IWUSR,
62		   show_intc_userimask, store_intc_userimask);
63
64
65static 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}
80late_initcall(userimask_sysdev_init);
81
82int 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}