isc.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Functions for registration of I/O interruption subclasses on s390.
 4 *
 5 * Copyright IBM Corp. 2008
 6 * Authors: Sebastian Ott <sebott@linux.vnet.ibm.com>
 7 */
 8
 9#include <linux/spinlock.h>
10#include <linux/export.h>
11#include <linux/module.h>
12#include <asm/isc.h>
13
14static unsigned int isc_refs[MAX_ISC + 1];
15static DEFINE_SPINLOCK(isc_ref_lock);
16
17
18/**
19 * isc_register - register an I/O interruption subclass.
20 * @isc: I/O interruption subclass to register
21 *
22 * The number of users for @isc is increased. If this is the first user to
23 * register @isc, the corresponding I/O interruption subclass mask is enabled.
24 *
25 * Context:
26 *   This function must not be called in interrupt context.
27 */
28void isc_register(unsigned int isc)
29{
30	if (isc > MAX_ISC) {
31		WARN_ON(1);
32		return;
33	}
34
35	spin_lock(&isc_ref_lock);
36	if (isc_refs[isc] == 0)
37		system_ctl_set_bit(6, 31 - isc);
38	isc_refs[isc]++;
39	spin_unlock(&isc_ref_lock);
40}
41EXPORT_SYMBOL_GPL(isc_register);
42
43/**
44 * isc_unregister - unregister an I/O interruption subclass.
45 * @isc: I/O interruption subclass to unregister
46 *
47 * The number of users for @isc is decreased. If this is the last user to
48 * unregister @isc, the corresponding I/O interruption subclass mask is
49 * disabled.
50 * Note: This function must not be called if isc_register() hasn't been called
51 * before by the driver for @isc.
52 *
53 * Context:
54 *   This function must not be called in interrupt context.
55 */
56void isc_unregister(unsigned int isc)
57{
58	spin_lock(&isc_ref_lock);
59	/* check for misuse */
60	if (isc > MAX_ISC || isc_refs[isc] == 0) {
61		WARN_ON(1);
62		goto out_unlock;
63	}
64	if (isc_refs[isc] == 1)
65		system_ctl_clear_bit(6, 31 - isc);
66	isc_refs[isc]--;
67out_unlock:
68	spin_unlock(&isc_ref_lock);
69}
70EXPORT_SYMBOL_GPL(isc_unregister);