1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * PowerNV OPAL asynchronous completion interfaces
4 *
5 * Copyright 2013-2017 IBM Corp.
6 */
7
8#undef DEBUG
9
10#include <linux/kernel.h>
11#include <linux/init.h>
12#include <linux/slab.h>
13#include <linux/sched.h>
14#include <linux/semaphore.h>
15#include <linux/spinlock.h>
16#include <linux/wait.h>
17#include <linux/gfp.h>
18#include <linux/of.h>
19#include <asm/machdep.h>
20#include <asm/opal.h>
21
22enum opal_async_token_state {
23	ASYNC_TOKEN_UNALLOCATED = 0,
24	ASYNC_TOKEN_ALLOCATED,
25	ASYNC_TOKEN_DISPATCHED,
26	ASYNC_TOKEN_ABANDONED,
27	ASYNC_TOKEN_COMPLETED
28};
29
30struct opal_async_token {
31	enum opal_async_token_state state;
32	struct opal_msg response;
33};
34
35static DECLARE_WAIT_QUEUE_HEAD(opal_async_wait);
36static DEFINE_SPINLOCK(opal_async_comp_lock);
37static struct semaphore opal_async_sem;
38static unsigned int opal_max_async_tokens;
39static struct opal_async_token *opal_async_tokens;
40
41static int __opal_async_get_token(void)
42{
43	unsigned long flags;
44	int i, token = -EBUSY;
45
46	spin_lock_irqsave(&opal_async_comp_lock, flags);
47
48	for (i = 0; i < opal_max_async_tokens; i++) {
49		if (opal_async_tokens[i].state == ASYNC_TOKEN_UNALLOCATED) {
50			opal_async_tokens[i].state = ASYNC_TOKEN_ALLOCATED;
51			token = i;
52			break;
53		}
54	}
55
56	spin_unlock_irqrestore(&opal_async_comp_lock, flags);
57	return token;
58}
59
60/*
61 * Note: If the returned token is used in an opal call and opal returns
62 * OPAL_ASYNC_COMPLETION you MUST call one of opal_async_wait_response() or
63 * opal_async_wait_response_interruptible() at least once before calling another
64 * opal_async_* function
65 */
66int opal_async_get_token_interruptible(void)
67{
68	int token;
69
70	/* Wait until a token is available */
71	if (down_interruptible(&opal_async_sem))
72		return -ERESTARTSYS;
73
74	token = __opal_async_get_token();
75	if (token < 0)
76		up(&opal_async_sem);
77
78	return token;
79}
80EXPORT_SYMBOL_GPL(opal_async_get_token_interruptible);
81
82static int __opal_async_release_token(int token)
83{
84	unsigned long flags;
85	int rc;
86
87	if (token < 0 || token >= opal_max_async_tokens) {
88		pr_err("%s: Passed token is out of range, token %d\n",
89				__func__, token);
90		return -EINVAL;
91	}
92
93	spin_lock_irqsave(&opal_async_comp_lock, flags);
94	switch (opal_async_tokens[token].state) {
95	case ASYNC_TOKEN_COMPLETED:
96	case ASYNC_TOKEN_ALLOCATED:
97		opal_async_tokens[token].state = ASYNC_TOKEN_UNALLOCATED;
98		rc = 0;
99		break;
100	/*
101	 * DISPATCHED and ABANDONED tokens must wait for OPAL to respond.
102	 * Mark a DISPATCHED token as ABANDONED so that the response handling
103	 * code knows no one cares and that it can free it then.
104	 */
105	case ASYNC_TOKEN_DISPATCHED:
106		opal_async_tokens[token].state = ASYNC_TOKEN_ABANDONED;
107		fallthrough;
108	default:
109		rc = 1;
110	}
111	spin_unlock_irqrestore(&opal_async_comp_lock, flags);
112
113	return rc;
114}
115
116int opal_async_release_token(int token)
117{
118	int ret;
119
120	ret = __opal_async_release_token(token);
121	if (!ret)
122		up(&opal_async_sem);
123
124	return ret;
125}
126EXPORT_SYMBOL_GPL(opal_async_release_token);
127
128int opal_async_wait_response(uint64_t token, struct opal_msg *msg)
129{
130	if (token >= opal_max_async_tokens) {
131		pr_err("%s: Invalid token passed\n", __func__);
132		return -EINVAL;
133	}
134
135	if (!msg) {
136		pr_err("%s: Invalid message pointer passed\n", __func__);
137		return -EINVAL;
138	}
139
140	/*
141	 * There is no need to mark the token as dispatched, wait_event()
142	 * will block until the token completes.
143	 *
144	 * Wakeup the poller before we wait for events to speed things
145	 * up on platforms or simulators where the interrupts aren't
146	 * functional.
147	 */
148	opal_wake_poller();
149	wait_event(opal_async_wait, opal_async_tokens[token].state
150			== ASYNC_TOKEN_COMPLETED);
151	memcpy(msg, &opal_async_tokens[token].response, sizeof(*msg));
152
153	return 0;
154}
155EXPORT_SYMBOL_GPL(opal_async_wait_response);
156
157int opal_async_wait_response_interruptible(uint64_t token, struct opal_msg *msg)
158{
159	unsigned long flags;
160	int ret;
161
162	if (token >= opal_max_async_tokens) {
163		pr_err("%s: Invalid token passed\n", __func__);
164		return -EINVAL;
165	}
166
167	if (!msg) {
168		pr_err("%s: Invalid message pointer passed\n", __func__);
169		return -EINVAL;
170	}
171
172	/*
173	 * The first time this gets called we mark the token as DISPATCHED
174	 * so that if wait_event_interruptible() returns not zero and the
175	 * caller frees the token, we know not to actually free the token
176	 * until the response comes.
177	 *
178	 * Only change if the token is ALLOCATED - it may have been
179	 * completed even before the caller gets around to calling this
180	 * the first time.
181	 *
182	 * There is also a dirty great comment at the token allocation
183	 * function that if the opal call returns OPAL_ASYNC_COMPLETION to
184	 * the caller then the caller *must* call this or the not
185	 * interruptible version before doing anything else with the
186	 * token.
187	 */
188	if (opal_async_tokens[token].state == ASYNC_TOKEN_ALLOCATED) {
189		spin_lock_irqsave(&opal_async_comp_lock, flags);
190		if (opal_async_tokens[token].state == ASYNC_TOKEN_ALLOCATED)
191			opal_async_tokens[token].state = ASYNC_TOKEN_DISPATCHED;
192		spin_unlock_irqrestore(&opal_async_comp_lock, flags);
193	}
194
195	/*
196	 * Wakeup the poller before we wait for events to speed things
197	 * up on platforms or simulators where the interrupts aren't
198	 * functional.
199	 */
200	opal_wake_poller();
201	ret = wait_event_interruptible(opal_async_wait,
202			opal_async_tokens[token].state ==
203			ASYNC_TOKEN_COMPLETED);
204	if (!ret)
205		memcpy(msg, &opal_async_tokens[token].response, sizeof(*msg));
206
207	return ret;
208}
209EXPORT_SYMBOL_GPL(opal_async_wait_response_interruptible);
210
211/* Called from interrupt context */
212static int opal_async_comp_event(struct notifier_block *nb,
213		unsigned long msg_type, void *msg)
214{
215	struct opal_msg *comp_msg = msg;
216	enum opal_async_token_state state;
217	unsigned long flags;
218	uint64_t token;
219
220	if (msg_type != OPAL_MSG_ASYNC_COMP)
221		return 0;
222
223	token = be64_to_cpu(comp_msg->params[0]);
224	spin_lock_irqsave(&opal_async_comp_lock, flags);
225	state = opal_async_tokens[token].state;
226	opal_async_tokens[token].state = ASYNC_TOKEN_COMPLETED;
227	spin_unlock_irqrestore(&opal_async_comp_lock, flags);
228
229	if (state == ASYNC_TOKEN_ABANDONED) {
230		/* Free the token, no one else will */
231		opal_async_release_token(token);
232		return 0;
233	}
234	memcpy(&opal_async_tokens[token].response, comp_msg, sizeof(*comp_msg));
235	wake_up(&opal_async_wait);
236
237	return 0;
238}
239
240static struct notifier_block opal_async_comp_nb = {
241		.notifier_call	= opal_async_comp_event,
242		.next		= NULL,
243		.priority	= 0,
244};
245
246int __init opal_async_comp_init(void)
247{
248	struct device_node *opal_node;
249	const __be32 *async;
250	int err;
251
252	opal_node = of_find_node_by_path("/ibm,opal");
253	if (!opal_node) {
254		pr_err("%s: Opal node not found\n", __func__);
255		err = -ENOENT;
256		goto out;
257	}
258
259	async = of_get_property(opal_node, "opal-msg-async-num", NULL);
260	if (!async) {
261		pr_err("%s: %pOF has no opal-msg-async-num\n",
262				__func__, opal_node);
263		err = -ENOENT;
264		goto out_opal_node;
265	}
266
267	opal_max_async_tokens = be32_to_cpup(async);
268	opal_async_tokens = kcalloc(opal_max_async_tokens,
269			sizeof(*opal_async_tokens), GFP_KERNEL);
270	if (!opal_async_tokens) {
271		err = -ENOMEM;
272		goto out_opal_node;
273	}
274
275	err = opal_message_notifier_register(OPAL_MSG_ASYNC_COMP,
276			&opal_async_comp_nb);
277	if (err) {
278		pr_err("%s: Can't register OPAL event notifier (%d)\n",
279				__func__, err);
280		kfree(opal_async_tokens);
281		goto out_opal_node;
282	}
283
284	sema_init(&opal_async_sem, opal_max_async_tokens);
285
286out_opal_node:
287	of_node_put(opal_node);
288out:
289	return err;
290}
291