void spm_hotplug_off(unsigned long mpidr)
{
unsigned long linear_id;
linear_id = platform_get_core_pos(mpidr);
spm_lock_get();
if (is_hotplug_ready() == 0) {
spm_mcdi_wakeup_all_cores();
mmio_clrbits_32(SPM_PCM_RESERVE, PCM_HOTPLUG_VALID_MASK);
spm_go_to_hotplug();
set_hotplug_ready();
}
mmio_clrsetbits_32(SPM_PCM_RESERVE, PCM_HOTPLUG_VALID_MASK,
(1 << linear_id) |
(1 << (linear_id + PCM_HOTPLUG_VALID_SHIFT)));
spm_lock_release();
}
/*
* This ensures that the hotplug operation can begin only when the
* refcount goes to zero.
*
* Note that during a cpu-hotplug operation, the new readers, if any,
* will be blocked by the cpu_hotplug.lock
*
* Since cpu_hotplug_begin() is always called after invoking
* cpu_maps_update_begin(), we can be sure that only one writer is active.
*
* Note that theoretically, there is a possibility of a livelock:
* - Refcount goes to zero, last reader wakes up the sleeping
* writer.
* - Last reader unlocks the cpu_hotplug.lock.
* - A new reader arrives at this moment, bumps up the refcount.
* - The writer acquires the cpu_hotplug.lock finds the refcount
* non zero and goes to sleep again.
*
* However, this is very difficult to achieve in practice since
* get_online_cpus() not an api which is called all that often.
*
*/
static void cpu_hotplug_begin(void)
{
cpu_hotplug.active_writer = current;
for (;;) {
mutex_lock(&cpu_hotplug.lock);
if (likely(!cpu_hotplug.refcount))
break;
__set_current_state(TASK_UNINTERRUPTIBLE);
mutex_unlock(&cpu_hotplug.lock);
schedule();
}
/*******************************************************************************
* 20131225 marc.huang *
* CPU Hotplug and idle integration *
*******************************************************************************/
atomic_inc(&is_in_hotplug);
spm_mcdi_wakeup_all_cores();
/******************************************************************************/
}
