1// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
2/******************************************************************************
3 *
4 * Module Name: evglock - Global Lock support
5 *
6 * Copyright (C) 2000 - 2023, Intel Corp.
7 *
8 *****************************************************************************/
9
10#include <acpi/acpi.h>
11#include "accommon.h"
12#include "acevents.h"
13#include "acinterp.h"
14
15#define _COMPONENT          ACPI_EVENTS
16ACPI_MODULE_NAME("evglock")
17#if (!ACPI_REDUCED_HARDWARE)	/* Entire module */
18/* Local prototypes */
19static u32 acpi_ev_global_lock_handler(void *context);
20
21/*******************************************************************************
22 *
23 * FUNCTION:    acpi_ev_init_global_lock_handler
24 *
25 * PARAMETERS:  None
26 *
27 * RETURN:      Status
28 *
29 * DESCRIPTION: Install a handler for the global lock release event
30 *
31 ******************************************************************************/
32
33acpi_status acpi_ev_init_global_lock_handler(void)
34{
35	acpi_status status;
36
37	ACPI_FUNCTION_TRACE(ev_init_global_lock_handler);
38
39	/* If Hardware Reduced flag is set, there is no global lock */
40
41	if (acpi_gbl_reduced_hardware) {
42		return_ACPI_STATUS(AE_OK);
43	}
44
45	/* Attempt installation of the global lock handler */
46
47	status = acpi_install_fixed_event_handler(ACPI_EVENT_GLOBAL,
48						  acpi_ev_global_lock_handler,
49						  NULL);
50
51	/*
52	 * If the global lock does not exist on this platform, the attempt to
53	 * enable GBL_STATUS will fail (the GBL_ENABLE bit will not stick).
54	 * Map to AE_OK, but mark global lock as not present. Any attempt to
55	 * actually use the global lock will be flagged with an error.
56	 */
57	acpi_gbl_global_lock_present = FALSE;
58	if (status == AE_NO_HARDWARE_RESPONSE) {
59		ACPI_ERROR((AE_INFO,
60			    "No response from Global Lock hardware, disabling lock"));
61
62		return_ACPI_STATUS(AE_OK);
63	}
64
65	status = acpi_os_create_lock(&acpi_gbl_global_lock_pending_lock);
66	if (ACPI_FAILURE(status)) {
67		return_ACPI_STATUS(status);
68	}
69
70	acpi_gbl_global_lock_pending = FALSE;
71	acpi_gbl_global_lock_present = TRUE;
72	return_ACPI_STATUS(status);
73}
74
75/*******************************************************************************
76 *
77 * FUNCTION:    acpi_ev_remove_global_lock_handler
78 *
79 * PARAMETERS:  None
80 *
81 * RETURN:      Status
82 *
83 * DESCRIPTION: Remove the handler for the Global Lock
84 *
85 ******************************************************************************/
86
87acpi_status acpi_ev_remove_global_lock_handler(void)
88{
89	acpi_status status;
90
91	ACPI_FUNCTION_TRACE(ev_remove_global_lock_handler);
92
93	acpi_gbl_global_lock_present = FALSE;
94	status = acpi_remove_fixed_event_handler(ACPI_EVENT_GLOBAL,
95						 acpi_ev_global_lock_handler);
96
97	acpi_os_delete_lock(acpi_gbl_global_lock_pending_lock);
98	return_ACPI_STATUS(status);
99}
100
101/*******************************************************************************
102 *
103 * FUNCTION:    acpi_ev_global_lock_handler
104 *
105 * PARAMETERS:  context         - From thread interface, not used
106 *
107 * RETURN:      ACPI_INTERRUPT_HANDLED
108 *
109 * DESCRIPTION: Invoked directly from the SCI handler when a global lock
110 *              release interrupt occurs. If there is actually a pending
111 *              request for the lock, signal the waiting thread.
112 *
113 ******************************************************************************/
114
115static u32 acpi_ev_global_lock_handler(void *context)
116{
117	acpi_status status;
118	acpi_cpu_flags flags;
119
120	flags = acpi_os_acquire_lock(acpi_gbl_global_lock_pending_lock);
121
122	/*
123	 * If a request for the global lock is not actually pending,
124	 * we are done. This handles "spurious" global lock interrupts
125	 * which are possible (and have been seen) with bad BIOSs.
126	 */
127	if (!acpi_gbl_global_lock_pending) {
128		goto cleanup_and_exit;
129	}
130
131	/*
132	 * Send a unit to the global lock semaphore. The actual acquisition
133	 * of the global lock will be performed by the waiting thread.
134	 */
135	status = acpi_os_signal_semaphore(acpi_gbl_global_lock_semaphore, 1);
136	if (ACPI_FAILURE(status)) {
137		ACPI_ERROR((AE_INFO, "Could not signal Global Lock semaphore"));
138	}
139
140	acpi_gbl_global_lock_pending = FALSE;
141
142cleanup_and_exit:
143
144	acpi_os_release_lock(acpi_gbl_global_lock_pending_lock, flags);
145	return (ACPI_INTERRUPT_HANDLED);
146}
147
148/******************************************************************************
149 *
150 * FUNCTION:    acpi_ev_acquire_global_lock
151 *
152 * PARAMETERS:  timeout         - Max time to wait for the lock, in millisec.
153 *
154 * RETURN:      Status
155 *
156 * DESCRIPTION: Attempt to gain ownership of the Global Lock.
157 *
158 * MUTEX:       Interpreter must be locked
159 *
160 * Note: The original implementation allowed multiple threads to "acquire" the
161 * Global Lock, and the OS would hold the lock until the last thread had
162 * released it. However, this could potentially starve the BIOS out of the
163 * lock, especially in the case where there is a tight handshake between the
164 * Embedded Controller driver and the BIOS. Therefore, this implementation
165 * allows only one thread to acquire the HW Global Lock at a time, and makes
166 * the global lock appear as a standard mutex on the OS side.
167 *
168 *****************************************************************************/
169
170acpi_status acpi_ev_acquire_global_lock(u16 timeout)
171{
172	acpi_cpu_flags flags;
173	acpi_status status;
174	u8 acquired = FALSE;
175
176	ACPI_FUNCTION_TRACE(ev_acquire_global_lock);
177
178	/*
179	 * Only one thread can acquire the GL at a time, the global_lock_mutex
180	 * enforces this. This interface releases the interpreter if we must wait.
181	 */
182	status =
183	    acpi_ex_system_wait_mutex(acpi_gbl_global_lock_mutex->mutex.
184				      os_mutex, timeout);
185	if (ACPI_FAILURE(status)) {
186		return_ACPI_STATUS(status);
187	}
188
189	/*
190	 * Update the global lock handle and check for wraparound. The handle is
191	 * only used for the external global lock interfaces, but it is updated
192	 * here to properly handle the case where a single thread may acquire the
193	 * lock via both the AML and the acpi_acquire_global_lock interfaces. The
194	 * handle is therefore updated on the first acquire from a given thread
195	 * regardless of where the acquisition request originated.
196	 */
197	acpi_gbl_global_lock_handle++;
198	if (acpi_gbl_global_lock_handle == 0) {
199		acpi_gbl_global_lock_handle = 1;
200	}
201
202	/*
203	 * Make sure that a global lock actually exists. If not, just
204	 * treat the lock as a standard mutex.
205	 */
206	if (!acpi_gbl_global_lock_present) {
207		acpi_gbl_global_lock_acquired = TRUE;
208		return_ACPI_STATUS(AE_OK);
209	}
210
211	flags = acpi_os_acquire_lock(acpi_gbl_global_lock_pending_lock);
212
213	do {
214
215		/* Attempt to acquire the actual hardware lock */
216
217		ACPI_ACQUIRE_GLOBAL_LOCK(acpi_gbl_FACS, acquired);
218		if (acquired) {
219			acpi_gbl_global_lock_acquired = TRUE;
220			ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
221					  "Acquired hardware Global Lock\n"));
222			break;
223		}
224
225		/*
226		 * Did not get the lock. The pending bit was set above, and
227		 * we must now wait until we receive the global lock
228		 * released interrupt.
229		 */
230		acpi_gbl_global_lock_pending = TRUE;
231		acpi_os_release_lock(acpi_gbl_global_lock_pending_lock, flags);
232
233		ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
234				  "Waiting for hardware Global Lock\n"));
235
236		/*
237		 * Wait for handshake with the global lock interrupt handler.
238		 * This interface releases the interpreter if we must wait.
239		 */
240		status =
241		    acpi_ex_system_wait_semaphore
242		    (acpi_gbl_global_lock_semaphore, ACPI_WAIT_FOREVER);
243
244		flags = acpi_os_acquire_lock(acpi_gbl_global_lock_pending_lock);
245
246	} while (ACPI_SUCCESS(status));
247
248	acpi_gbl_global_lock_pending = FALSE;
249	acpi_os_release_lock(acpi_gbl_global_lock_pending_lock, flags);
250
251	return_ACPI_STATUS(status);
252}
253
254/*******************************************************************************
255 *
256 * FUNCTION:    acpi_ev_release_global_lock
257 *
258 * PARAMETERS:  None
259 *
260 * RETURN:      Status
261 *
262 * DESCRIPTION: Releases ownership of the Global Lock.
263 *
264 ******************************************************************************/
265
266acpi_status acpi_ev_release_global_lock(void)
267{
268	u8 pending = FALSE;
269	acpi_status status = AE_OK;
270
271	ACPI_FUNCTION_TRACE(ev_release_global_lock);
272
273	/* Lock must be already acquired */
274
275	if (!acpi_gbl_global_lock_acquired) {
276		ACPI_WARNING((AE_INFO,
277			      "Cannot release the ACPI Global Lock, it has not been acquired"));
278		return_ACPI_STATUS(AE_NOT_ACQUIRED);
279	}
280
281	if (acpi_gbl_global_lock_present) {
282
283		/* Allow any thread to release the lock */
284
285		ACPI_RELEASE_GLOBAL_LOCK(acpi_gbl_FACS, pending);
286
287		/*
288		 * If the pending bit was set, we must write GBL_RLS to the control
289		 * register
290		 */
291		if (pending) {
292			status =
293			    acpi_write_bit_register
294			    (ACPI_BITREG_GLOBAL_LOCK_RELEASE,
295			     ACPI_ENABLE_EVENT);
296		}
297
298		ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
299				  "Released hardware Global Lock\n"));
300	}
301
302	acpi_gbl_global_lock_acquired = FALSE;
303
304	/* Release the local GL mutex */
305
306	acpi_os_release_mutex(acpi_gbl_global_lock_mutex->mutex.os_mutex);
307	return_ACPI_STATUS(status);
308}
309
310#endif				/* !ACPI_REDUCED_HARDWARE */
311