// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 /****************************************************************************** * * Module Name: evglock - Global Lock support * * Copyright (C) 2000 - 2025, Intel Corp. * *****************************************************************************/ #include <acpi/acpi.h> #include "accommon.h" #include "acevents.h" #include "acinterp.h" #define _COMPONENT ACPI_EVENTS ACPI_MODULE_NAME("evglock") #if (!ACPI_REDUCED_HARDWARE) /* Entire module */ /* Local prototypes */ static u32 acpi_ev_global_lock_handler(void *context); /******************************************************************************* * * FUNCTION: acpi_ev_init_global_lock_handler * * PARAMETERS: None * * RETURN: Status * * DESCRIPTION: Install a handler for the global lock release event * ******************************************************************************/ acpi_status acpi_ev_init_global_lock_handler(void) { acpi_status status; ACPI_FUNCTION_TRACE(ev_init_global_lock_handler); /* If Hardware Reduced flag is set, there is no global lock */ if (acpi_gbl_reduced_hardware) { return_ACPI_STATUS(AE_OK); } if (!acpi_gbl_use_global_lock) { return_ACPI_STATUS(AE_OK); } /* Attempt installation of the global lock handler */ status = acpi_install_fixed_event_handler(ACPI_EVENT_GLOBAL, acpi_ev_global_lock_handler, NULL); /* * If the global lock does not exist on this platform, the attempt to * enable GBL_STATUS will fail (the GBL_ENABLE bit will not stick). * Map to AE_OK, but mark global lock as not present. Any attempt to * actually use the global lock will be flagged with an error. */ acpi_gbl_global_lock_present = FALSE; if (status == AE_NO_HARDWARE_RESPONSE) { ACPI_ERROR((AE_INFO, "No response from Global Lock hardware, disabling lock")); return_ACPI_STATUS(AE_OK); } status = acpi_os_create_lock(&acpi_gbl_global_lock_pending_lock); if (ACPI_FAILURE(status)) { return_ACPI_STATUS(status); } acpi_gbl_global_lock_pending = FALSE; acpi_gbl_global_lock_present = TRUE; return_ACPI_STATUS(status); } /******************************************************************************* * * FUNCTION: acpi_ev_remove_global_lock_handler * * PARAMETERS: None * * RETURN: Status * * DESCRIPTION: Remove the handler for the Global Lock * ******************************************************************************/ acpi_status acpi_ev_remove_global_lock_handler(void) { acpi_status status; ACPI_FUNCTION_TRACE(ev_remove_global_lock_handler); acpi_gbl_global_lock_present = FALSE; status = acpi_remove_fixed_event_handler(ACPI_EVENT_GLOBAL, acpi_ev_global_lock_handler); acpi_os_delete_lock(acpi_gbl_global_lock_pending_lock); return_ACPI_STATUS(status); } /******************************************************************************* * * FUNCTION: acpi_ev_global_lock_handler * * PARAMETERS: context - From thread interface, not used * * RETURN: ACPI_INTERRUPT_HANDLED * * DESCRIPTION: Invoked directly from the SCI handler when a global lock * release interrupt occurs. If there is actually a pending * request for the lock, signal the waiting thread. * ******************************************************************************/ static u32 acpi_ev_global_lock_handler(void *context) { acpi_status status; acpi_cpu_flags flags; flags = acpi_os_acquire_lock(acpi_gbl_global_lock_pending_lock); /* * If a request for the global lock is not actually pending, * we are done. This handles "spurious" global lock interrupts * which are possible (and have been seen) with bad BIOSs. */ if (!acpi_gbl_global_lock_pending) { goto cleanup_and_exit; } /* * Send a unit to the global lock semaphore. The actual acquisition * of the global lock will be performed by the waiting thread. */ status = acpi_os_signal_semaphore(acpi_gbl_global_lock_semaphore, 1); if (ACPI_FAILURE(status)) { ACPI_ERROR((AE_INFO, "Could not signal Global Lock semaphore")); } acpi_gbl_global_lock_pending = FALSE; cleanup_and_exit: acpi_os_release_lock(acpi_gbl_global_lock_pending_lock, flags); return (ACPI_INTERRUPT_HANDLED); } /****************************************************************************** * * FUNCTION: acpi_ev_acquire_global_lock * * PARAMETERS: timeout - Max time to wait for the lock, in millisec. * * RETURN: Status * * DESCRIPTION: Attempt to gain ownership of the Global Lock. * * MUTEX: Interpreter must be locked * * Note: The original implementation allowed multiple threads to "acquire" the * Global Lock, and the OS would hold the lock until the last thread had * released it. However, this could potentially starve the BIOS out of the * lock, especially in the case where there is a tight handshake between the * Embedded Controller driver and the BIOS. Therefore, this implementation * allows only one thread to acquire the HW Global Lock at a time, and makes * the global lock appear as a standard mutex on the OS side. * *****************************************************************************/ acpi_status acpi_ev_acquire_global_lock(u16 timeout) { acpi_cpu_flags flags; acpi_status status; u8 acquired = FALSE; ACPI_FUNCTION_TRACE(ev_acquire_global_lock); /* * Only one thread can acquire the GL at a time, the global_lock_mutex * enforces this. This interface releases the interpreter if we must wait. */ status = acpi_ex_system_wait_mutex(acpi_gbl_global_lock_mutex->mutex. os_mutex, timeout); if (ACPI_FAILURE(status)) { return_ACPI_STATUS(status); } /* * Update the global lock handle and check for wraparound. The handle is * only used for the external global lock interfaces, but it is updated * here to properly handle the case where a single thread may acquire the * lock via both the AML and the acpi_acquire_global_lock interfaces. The * handle is therefore updated on the first acquire from a given thread * regardless of where the acquisition request originated. */ acpi_gbl_global_lock_handle++; if (acpi_gbl_global_lock_handle == 0) { acpi_gbl_global_lock_handle = 1; } /* * Make sure that a global lock actually exists. If not, just * treat the lock as a standard mutex. */ if (!acpi_gbl_global_lock_present) { acpi_gbl_global_lock_acquired = TRUE; return_ACPI_STATUS(AE_OK); } flags = acpi_os_acquire_lock(acpi_gbl_global_lock_pending_lock); do { /* Attempt to acquire the actual hardware lock */ ACPI_ACQUIRE_GLOBAL_LOCK(acpi_gbl_FACS, acquired); if (acquired) { acpi_gbl_global_lock_acquired = TRUE; ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Acquired hardware Global Lock\n")); break; } /* * Did not get the lock. The pending bit was set above, and * we must now wait until we receive the global lock * released interrupt. */ acpi_gbl_global_lock_pending = TRUE; acpi_os_release_lock(acpi_gbl_global_lock_pending_lock, flags); ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Waiting for hardware Global Lock\n")); /* * Wait for handshake with the global lock interrupt handler. * This interface releases the interpreter if we must wait. */ status = acpi_ex_system_wait_semaphore (acpi_gbl_global_lock_semaphore, ACPI_WAIT_FOREVER); flags = acpi_os_acquire_lock(acpi_gbl_global_lock_pending_lock); } while (ACPI_SUCCESS(status)); acpi_gbl_global_lock_pending = FALSE; acpi_os_release_lock(acpi_gbl_global_lock_pending_lock, flags); return_ACPI_STATUS(status); } /******************************************************************************* * * FUNCTION: acpi_ev_release_global_lock * * PARAMETERS: None * * RETURN: Status * * DESCRIPTION: Releases ownership of the Global Lock. * ******************************************************************************/ acpi_status acpi_ev_release_global_lock(void) { u8 pending = FALSE; acpi_status status = AE_OK; ACPI_FUNCTION_TRACE(ev_release_global_lock); /* Lock must be already acquired */ if (!acpi_gbl_global_lock_acquired) { ACPI_WARNING((AE_INFO, "Cannot release the ACPI Global Lock, it has not been acquired")); return_ACPI_STATUS(AE_NOT_ACQUIRED); } if (acpi_gbl_global_lock_present) { /* Allow any thread to release the lock */ ACPI_RELEASE_GLOBAL_LOCK(acpi_gbl_FACS, pending); /* * If the pending bit was set, we must write GBL_RLS to the control * register */ if (pending) { status = acpi_write_bit_register (ACPI_BITREG_GLOBAL_LOCK_RELEASE, ACPI_ENABLE_EVENT); } ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Released hardware Global Lock\n")); } acpi_gbl_global_lock_acquired = FALSE; /* Release the local GL mutex */ acpi_os_release_mutex(acpi_gbl_global_lock_mutex->mutex.os_mutex); return_ACPI_STATUS(status); } #endif /* !ACPI_REDUCED_HARDWARE */
