1/*
2 *  Copyright (C) 2009 Imagination Technologies
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 * The Meta KICK interrupt mechanism is generally a useful feature, so
9 * we provide an interface for registering multiple interrupt
10 * handlers. All the registered interrupt handlers are "chained". When
11 * a KICK interrupt is received the first function in the list is
12 * called. If that interrupt handler cannot handle the KICK the next
13 * one is called, then the next until someone handles it (or we run
14 * out of functions). As soon as one function handles the interrupt no
15 * other handlers are called.
16 *
17 * The only downside of chaining interrupt handlers is that each
18 * handler must be able to detect whether the KICK was intended for it
19 * or not.  For example, when the IPI handler runs and it sees that
20 * there are no IPI messages it must not signal that the KICK was
21 * handled, thereby giving the other handlers a chance to run.
22 *
23 * The reason that we provide our own interface for calling KICK
24 * handlers instead of using the generic kernel infrastructure is that
25 * the KICK handlers require access to a CPU's pTBI structure. So we
26 * pass it as an argument.
27 */
28#include <linux/export.h>
29#include <linux/hardirq.h>
30#include <linux/irq.h>
31#include <linux/kernel.h>
32#include <linux/mm.h>
33#include <linux/types.h>
34
35#include <asm/traps.h>
36
37/*
38 * All accesses/manipulations of kick_handlers_list should be
39 * performed while holding kick_handlers_lock.
40 */
41static DEFINE_SPINLOCK(kick_handlers_lock);
42static LIST_HEAD(kick_handlers_list);
43
44void kick_register_func(struct kick_irq_handler *kh)
45{
46	unsigned long flags;
47
48	spin_lock_irqsave(&kick_handlers_lock, flags);
49
50	list_add_tail(&kh->list, &kick_handlers_list);
51
52	spin_unlock_irqrestore(&kick_handlers_lock, flags);
53}
54EXPORT_SYMBOL(kick_register_func);
55
56void kick_unregister_func(struct kick_irq_handler *kh)
57{
58	unsigned long flags;
59
60	spin_lock_irqsave(&kick_handlers_lock, flags);
61
62	list_del(&kh->list);
63
64	spin_unlock_irqrestore(&kick_handlers_lock, flags);
65}
66EXPORT_SYMBOL(kick_unregister_func);
67
68TBIRES
69kick_handler(TBIRES State, int SigNum, int Triggers, int Inst, PTBI pTBI)
70{
71	struct pt_regs *old_regs;
72	struct kick_irq_handler *kh;
73	struct list_head *lh;
74	int handled = 0;
75	TBIRES ret;
76
77	head_end(State, ~INTS_OFF_MASK);
78
79	/* If we interrupted user code handle any critical sections. */
80	if (State.Sig.SaveMask & TBICTX_PRIV_BIT)
81		restart_critical_section(State);
82
83	trace_hardirqs_off();
84
85	old_regs = set_irq_regs((struct pt_regs *)State.Sig.pCtx);
86	irq_enter();
87
88	/*
89	 * There is no need to disable interrupts here because we
90	 * can't nest KICK interrupts in a KICK interrupt handler.
91	 */
92	spin_lock(&kick_handlers_lock);
93
94	list_for_each(lh, &kick_handlers_list) {
95		kh = list_entry(lh, struct kick_irq_handler, list);
96
97		ret = kh->func(State, SigNum, Triggers, Inst, pTBI, &handled);
98		if (handled)
99			break;
100	}
101
102	spin_unlock(&kick_handlers_lock);
103
104	WARN_ON(!handled);
105
106	irq_exit();
107	set_irq_regs(old_regs);
108
109	return tail_end(ret);
110}
111