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
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
58static DEVICE_ATTR(userimask, S_IRUSR | S_IWUSR,
59		   show_intc_userimask, store_intc_userimask);
60
61
62static 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}
77late_initcall(userimask_sysdev_init);
78
79int 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