text: /******************************************************************************
   *
   * Module Name: evglock - Global Lock support
   *
   *****************************************************************************/
  
  /*
   * Copyright (C) 2000 - 2015, Intel Corp.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions, and the following disclaimer,
   *    without modification.
   * 2. Redistributions in binary form must reproduce at minimum a disclaimer
   *    substantially similar to the "NO WARRANTY" disclaimer below
   *    ("Disclaimer") and any redistribution must be conditioned upon
   *    including a substantially similar Disclaimer requirement for further
   *    binary redistribution.
   * 3. Neither the names of the above-listed copyright holders nor the names
   *    of any contributors may be used to endorse or promote products derived
   *    from this software without specific prior written permission.
   *
   * Alternatively, this software may be distributed under the terms of the
   * GNU General Public License ("GPL") version 2 as published by the Free
   * Software Foundation.
   *
   * NO WARRANTY
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGES.
   */
  
  #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);
  	}
  
  	/* 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 */
  