Revert "msm: mdss: Remove distinction between positive and negative polarities"

This reverts commit 3b807e9140b031167b5d0811c41a05d59bbbd2f2.
auto_hotplug: change parameter permissions
cpufreq: cpu-boost: Resolve deadlock when waking up sync thread

CPU boost driver receives notification from scheduler when threads
migrate towards a cpu and in turn wakes up a sync thread associated
with that cpu to handle any required frequency transitions. The wakeup
call however can lead to a deadlock inside scheduler under some
circumstance. The deadlock is seen when sync thread is the only thread
running on a cpu and goes to sleep (say by calling wait_event() ->
schedule()). Midway through this sleep (schedule()) call, while cpu is
still running in context of sync thread, scheduler attempts a load
balance (realizing that cpu is about to become idle) which can result
in tasks being migrated towards the cpu going idle. This will cause
migration notification to be issued and in turn a wakeup on sync
thread. The wakeup call however gets stuck in below while() loop
inside scheduler:

try_to_wake_up(struct task_struct *p, ...)
{

        /*
         * If the owning (remote) cpu is still in the middle of
	 * schedule() with this task as prev, wait until its done
	 * referencing the task.
         */
	while (p->on_cpu)
		cpu_relax();

}

A possible fix could be to teach try_to_wake_up() about this
special case. Another fix, implemented in this patch and that helps
minimize scheduler changes, is to have cpu boost driver not issue a
wakeup under this special circumstance, which was found to occur very
infrequently.

Change-Id: I92bc68a22d51595a208673fe2a1eedfa97004f9e
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>
cpufreq: cpu-boost: Fix deadlock in wake_up of sync threads

If wake_up() is called on the current task on a CPU, the call will wait
until the current task is switched out before it wakes it up again and
returns.

The sync notifier for a CPU always runs on that CPU.

These two together can result in a deadlock if the sync notifier on CPU A
tries to wake up the sync thread of CPU A as it goes to sleep (is the
current task). A previous commit fixed this by adding a check to the sync
notifier to not wake up the sync thread of CPU A if it's the current task.

But this is still not sufficient to prevent deadlocks.

Sync thread of CPU A could be the current task on CPU B and sync thread of
CPU B could be the current task on CPU A.  At this point, if sync notifier
of CPU A and B try to wake up the sync threads of CPU A and B, it will
result in CPU A waiting for the current task in CPU B to get switched out
and CPU B waiting for the current task in CPU A to get switched out.  This
will result in a deadlock.

Prevent this scenario from happening by pinning the sync threads of each
CPU to run on that CPU. By doing this, we guarantee that sync notifiers
will only try to wake up sync threads running on that CPU. The fix added by
"cpufreq: cpu-boost: Resolve deadlock when waking up sync thread" ensures a
deadlock doesn't happen when a sync notifier tries to wake up a sync thread
running on that CPU.

Change-Id: I864e545529722a23886dd5a82f66089155d2d193
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: revjunkie <gadgetjuan@gmail.com>