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 - 2025, 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 if (!acpi_gbl_use_global_lock) {
46 return_ACPI_STATUS(AE_OK);
47 }
48
49 /* Attempt installation of the global lock handler */
50
51 status = acpi_install_fixed_event_handler(ACPI_EVENT_GLOBAL,
52 handler: acpi_ev_global_lock_handler,
53 NULL);
54
55 /*
56 * If the global lock does not exist on this platform, the attempt to
57 * enable GBL_STATUS will fail (the GBL_ENABLE bit will not stick).
58 * Map to AE_OK, but mark global lock as not present. Any attempt to
59 * actually use the global lock will be flagged with an error.
60 */
61 acpi_gbl_global_lock_present = FALSE;
62 if (status == AE_NO_HARDWARE_RESPONSE) {
63 ACPI_ERROR((AE_INFO,
64 "No response from Global Lock hardware, disabling lock"));
65
66 return_ACPI_STATUS(AE_OK);
67 }
68
69 status = acpi_os_create_lock(&acpi_gbl_global_lock_pending_lock);
70 if (ACPI_FAILURE(status)) {
71 return_ACPI_STATUS(status);
72 }
73
74 acpi_gbl_global_lock_pending = FALSE;
75 acpi_gbl_global_lock_present = TRUE;
76 return_ACPI_STATUS(status);
77}
78
79/*******************************************************************************
80 *
81 * FUNCTION: acpi_ev_remove_global_lock_handler
82 *
83 * PARAMETERS: None
84 *
85 * RETURN: Status
86 *
87 * DESCRIPTION: Remove the handler for the Global Lock
88 *
89 ******************************************************************************/
90
91acpi_status acpi_ev_remove_global_lock_handler(void)
92{
93 acpi_status status;
94
95 ACPI_FUNCTION_TRACE(ev_remove_global_lock_handler);
96
97 acpi_gbl_global_lock_present = FALSE;
98 status = acpi_remove_fixed_event_handler(ACPI_EVENT_GLOBAL,
99 handler: acpi_ev_global_lock_handler);
100
101 acpi_os_delete_lock(handle: acpi_gbl_global_lock_pending_lock);
102 return_ACPI_STATUS(status);
103}
104
105/*******************************************************************************
106 *
107 * FUNCTION: acpi_ev_global_lock_handler
108 *
109 * PARAMETERS: context - From thread interface, not used
110 *
111 * RETURN: ACPI_INTERRUPT_HANDLED
112 *
113 * DESCRIPTION: Invoked directly from the SCI handler when a global lock
114 * release interrupt occurs. If there is actually a pending
115 * request for the lock, signal the waiting thread.
116 *
117 ******************************************************************************/
118
119static u32 acpi_ev_global_lock_handler(void *context)
120{
121 acpi_status status;
122 acpi_cpu_flags flags;
123
124 flags = acpi_os_acquire_lock(handle: acpi_gbl_global_lock_pending_lock);
125
126 /*
127 * If a request for the global lock is not actually pending,
128 * we are done. This handles "spurious" global lock interrupts
129 * which are possible (and have been seen) with bad BIOSs.
130 */
131 if (!acpi_gbl_global_lock_pending) {
132 goto cleanup_and_exit;
133 }
134
135 /*
136 * Send a unit to the global lock semaphore. The actual acquisition
137 * of the global lock will be performed by the waiting thread.
138 */
139 status = acpi_os_signal_semaphore(handle: acpi_gbl_global_lock_semaphore, units: 1);
140 if (ACPI_FAILURE(status)) {
141 ACPI_ERROR((AE_INFO, "Could not signal Global Lock semaphore"));
142 }
143
144 acpi_gbl_global_lock_pending = FALSE;
145
146cleanup_and_exit:
147
148 acpi_os_release_lock(handle: acpi_gbl_global_lock_pending_lock, flags);
149 return (ACPI_INTERRUPT_HANDLED);
150}
151
152/******************************************************************************
153 *
154 * FUNCTION: acpi_ev_acquire_global_lock
155 *
156 * PARAMETERS: timeout - Max time to wait for the lock, in millisec.
157 *
158 * RETURN: Status
159 *
160 * DESCRIPTION: Attempt to gain ownership of the Global Lock.
161 *
162 * MUTEX: Interpreter must be locked
163 *
164 * Note: The original implementation allowed multiple threads to "acquire" the
165 * Global Lock, and the OS would hold the lock until the last thread had
166 * released it. However, this could potentially starve the BIOS out of the
167 * lock, especially in the case where there is a tight handshake between the
168 * Embedded Controller driver and the BIOS. Therefore, this implementation
169 * allows only one thread to acquire the HW Global Lock at a time, and makes
170 * the global lock appear as a standard mutex on the OS side.
171 *
172 *****************************************************************************/
173
174acpi_status acpi_ev_acquire_global_lock(u16 timeout)
175{
176 acpi_cpu_flags flags;
177 acpi_status status;
178 u8 acquired = FALSE;
179
180 ACPI_FUNCTION_TRACE(ev_acquire_global_lock);
181
182 /*
183 * Only one thread can acquire the GL at a time, the global_lock_mutex
184 * enforces this. This interface releases the interpreter if we must wait.
185 */
186 status =
187 acpi_ex_system_wait_mutex(mutex: acpi_gbl_global_lock_mutex->mutex.
188 os_mutex, timeout);
189 if (ACPI_FAILURE(status)) {
190 return_ACPI_STATUS(status);
191 }
192
193 /*
194 * Update the global lock handle and check for wraparound. The handle is
195 * only used for the external global lock interfaces, but it is updated
196 * here to properly handle the case where a single thread may acquire the
197 * lock via both the AML and the acpi_acquire_global_lock interfaces. The
198 * handle is therefore updated on the first acquire from a given thread
199 * regardless of where the acquisition request originated.
200 */
201 acpi_gbl_global_lock_handle++;
202 if (acpi_gbl_global_lock_handle == 0) {
203 acpi_gbl_global_lock_handle = 1;
204 }
205
206 /*
207 * Make sure that a global lock actually exists. If not, just
208 * treat the lock as a standard mutex.
209 */
210 if (!acpi_gbl_global_lock_present) {
211 acpi_gbl_global_lock_acquired = TRUE;
212 return_ACPI_STATUS(AE_OK);
213 }
214
215 flags = acpi_os_acquire_lock(handle: acpi_gbl_global_lock_pending_lock);
216
217 do {
218
219 /* Attempt to acquire the actual hardware lock */
220
221 ACPI_ACQUIRE_GLOBAL_LOCK(acpi_gbl_FACS, acquired);
222 if (acquired) {
223 acpi_gbl_global_lock_acquired = TRUE;
224 ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
225 "Acquired hardware Global Lock\n"));
226 break;
227 }
228
229 /*
230 * Did not get the lock. The pending bit was set above, and
231 * we must now wait until we receive the global lock
232 * released interrupt.
233 */
234 acpi_gbl_global_lock_pending = TRUE;
235 acpi_os_release_lock(handle: acpi_gbl_global_lock_pending_lock, flags);
236
237 ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
238 "Waiting for hardware Global Lock\n"));
239
240 /*
241 * Wait for handshake with the global lock interrupt handler.
242 * This interface releases the interpreter if we must wait.
243 */
244 status =
245 acpi_ex_system_wait_semaphore
246 (semaphore: acpi_gbl_global_lock_semaphore, ACPI_WAIT_FOREVER);
247
248 flags = acpi_os_acquire_lock(handle: acpi_gbl_global_lock_pending_lock);
249
250 } while (ACPI_SUCCESS(status));
251
252 acpi_gbl_global_lock_pending = FALSE;
253 acpi_os_release_lock(handle: acpi_gbl_global_lock_pending_lock, flags);
254
255 return_ACPI_STATUS(status);
256}
257
258/*******************************************************************************
259 *
260 * FUNCTION: acpi_ev_release_global_lock
261 *
262 * PARAMETERS: None
263 *
264 * RETURN: Status
265 *
266 * DESCRIPTION: Releases ownership of the Global Lock.
267 *
268 ******************************************************************************/
269
270acpi_status acpi_ev_release_global_lock(void)
271{
272 u8 pending = FALSE;
273 acpi_status status = AE_OK;
274
275 ACPI_FUNCTION_TRACE(ev_release_global_lock);
276
277 /* Lock must be already acquired */
278
279 if (!acpi_gbl_global_lock_acquired) {
280 ACPI_WARNING((AE_INFO,
281 "Cannot release the ACPI Global Lock, it has not been acquired"));
282 return_ACPI_STATUS(AE_NOT_ACQUIRED);
283 }
284
285 if (acpi_gbl_global_lock_present) {
286
287 /* Allow any thread to release the lock */
288
289 ACPI_RELEASE_GLOBAL_LOCK(acpi_gbl_FACS, pending);
290
291 /*
292 * If the pending bit was set, we must write GBL_RLS to the control
293 * register
294 */
295 if (pending) {
296 status =
297 acpi_write_bit_register
298 (ACPI_BITREG_GLOBAL_LOCK_RELEASE,
299 ACPI_ENABLE_EVENT);
300 }
301
302 ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
303 "Released hardware Global Lock\n"));
304 }
305
306 acpi_gbl_global_lock_acquired = FALSE;
307
308 /* Release the local GL mutex */
309
310 acpi_os_release_mutex(acpi_gbl_global_lock_mutex->mutex.os_mutex);
311 return_ACPI_STATUS(status);
312}
313
314#endif /* !ACPI_REDUCED_HARDWARE */
315