power.cxx

eCos操作系统源码

    // the policy callback will be changed while the system is running,
    // but just in case somebody installs a null pointer between the
    // check and the call...
    void        (*callback)(PowerController*, PowerMode, PowerMode, PowerMode, PowerMode) = __power_policy_callback;
    if (0 != callback) {
        (*callback)(controller, old_mode, controller->mode, desired_mode, controller->desired_mode);
    }
}

// power_doit() is responsible for a single iteration over the various controllers,
// aborting if there is a global mode change during the current iteration. The
// calling code, either power_thread_fn() or power_nothread_doit(), will take
// care of the higher-level iterating while there is work to be done.
//
// If a global mode change has been requested then the order in which the controllers
// are invoked is significant: front->back for lowering power modes, back->front for
// a higher power mode. If there are individual changes to be processed then
// arbitrarily front->back is used as well.
static inline void
power_doit()
{
    PowerController*    controller;

    abort_mode_change   = false;

    if (__power_desired_mode < __power_mode) {
        // The new mode is more active than the old one, so start with
        // the power controllers at the back of the table.
        for (controller = &(__POWER_END__) - 1; !abort_mode_change && (controller >= &(__POWER__[0])); controller--) {
            PowerMode   desired_mode;
            cyg_bool    change_this;
            
#ifdef CYGPKG_POWER_THREAD
            // Read the desired_mode and change_this flags atomically.
            cyg_scheduler_lock();
            desired_mode = controller->desired_mode;
            change_this  = controller->change_this;
            cyg_scheduler_unlock();
#else
            desired_mode = controller->desired_mode;
            change_this  = controller->change_this;
#endif
            // If this controller is not running at the desired mode, change it.
            if (desired_mode != controller->mode) {
                power_change_controller_mode(controller, desired_mode, change_this);
            }
        }
    } else {    // __power_desired_mode >= __power_mode.
        // Either a global mode change to a less active mode, or
        // one or more individual controller changes. Other than
        // iterating in a different direction, the code is the same
        // as above.
        for (controller = &(__POWER__[0]); !abort_mode_change && (controller != &(__POWER_END__)); controller++) {
            PowerMode   desired_mode;
            cyg_bool    change_this;
            
#ifdef CYGPKG_POWER_THREAD
            cyg_scheduler_lock();
            desired_mode = controller->desired_mode;
            change_this  = controller->change_this;
            cyg_scheduler_unlock();
#else
            desired_mode = controller->desired_mode;
            change_this  = controller->change_this;
#endif
            if (desired_mode != controller->mode) {
                power_change_controller_mode(controller, desired_mode, change_this);
            }
        }
    }

    // All of the controllers have been invoked. If there have been no
    // intervening calls to power_set_mode() (which would have updated
    // abort_mode_change) then we must now be running at the desired
    // global mode.
    if (!abort_mode_change) {
        __power_mode = __power_desired_mode;
    }
}

#ifdef CYGPKG_POWER_THREAD
static void
power_thread_fn(cyg_addrword_t param)
{
    for (;;) {
        // Currently idle. Wait for a request to change power modes.
        cyg_semaphore_wait(&power_thread_action);
        power_doit();
    }
}
#else
static inline void
power_nothread_doit()
{
    power_todo_count++;
    if (!power_doing_it) {
        power_doing_it = true;
        do {
            power_doit();
        } while (--power_todo_count > 0);
        power_doing_it = false;
    }
}
#endif

// ----------------------------------------------------------------------------
// The exported calls.

extern "C" void
power_set_controller_mode(PowerController* controller, PowerMode new_mode)
{
#ifdef CYGPKG_POWER_THREAD
    cyg_scheduler_lock();   // Protect against concurrent calls
#endif
    
    controller->desired_mode    = new_mode;
    controller->change_this     = true;

#ifdef CYGPKG_POWER_THREAD    
    cyg_scheduler_unlock();
    cyg_semaphore_post(&power_thread_action);
#else
    power_nothread_doit();
#endif    
}

extern "C" void
power_set_mode(PowerMode new_mode)
{
    PowerController*        controller;

#ifdef CYGPKG_POWER_THREAD
    cyg_scheduler_lock();
#endif
    
    __power_desired_mode    = new_mode;
    abort_mode_change       = true;
    // Update each controller. Most importantly, clear the
    // "change_this" flag in every power controller. The net result is
    // that power_set_mode() overrides any power_set_controller_mode()
    // operations that have not yet been processed, but future
    // power_set_controller_mode() calls will have the desired effect.
    for (controller = &(__POWER__[0]); controller != &(__POWER_END__); controller++) {
        if (controller->attached) {
            controller->change_this     = 0;
            controller->desired_mode    = new_mode;
        }
    }

#ifdef CYGPKG_POWER_THREAD    
    cyg_scheduler_unlock();
    cyg_semaphore_post(&power_thread_action);
#else
    power_nothread_doit();
#endif    
}

// ----------------------------------------------------------------------------
// Power management initialization. This gets called from
// power_data.cxx using a prioritized constructors. Doing this way
// minimizes the amount of data that is going to end up in libextras.a
// and hence in the final executable, allowing linker garbage collection
// to clean up as much as possible. The main operation here is to start
// up a separate power management thread when configured to do so.
//
// If no separate thread is being used then no run-time initialization
// is needed.
#ifdef CYGPKG_POWER_THREAD
extern "C" void
power_init(void)
{
    cyg_semaphore_init(&power_thread_action, 0);
    cyg_thread_create(CYGNUM_POWER_THREAD_PRIORITY,
                      &power_thread_fn,
                      (cyg_addrword_t) 0,
                      "Power management thread",
                      power_thread_stack,
                      CYGNUM_POWER_THREAD_STACKSIZE,
                      &power_thread_handle,
                      &power_thread
        );
    cyg_thread_resume(power_thread_handle);
}
#endif