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 - 2019, 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
16 ACPI_MODULE_NAME("evglock")
17 #if (!ACPI_REDUCED_HARDWARE) /* Entire module */
18 /* Local prototypes */
19 static 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
33 acpi_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
87 acpi_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
115 static 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
142 cleanup_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
170 acpi_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
266 acpi_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 */