evglock.c

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/******************************************************************************
 *
 * Module Name: evglock - Global Lock support
 *
 *****************************************************************************/

/*
 * Copyright (C) 2000 - 2012, 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);

    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 */