cpufreq: Fix optimal_freq logic on ramp down

When ondemand governor decides to ramp down the frequency, the missing
check for frequency being lower than optimal_freq was causing frequency
to be ramped down to optimal_freq even if the frequency decided by ondemand
governor was higher.

Change-Id: I00f9ae4c61ccda4039f3338dee2c29b8cb790be4
Signed-off-by: Veena Sambasivan <veenas@codeaurora.org>
msm: Synchronize CPU frequency on thread migration

Sometimes when foreground threads, crucial for UI, migrate
from a core at higher frequency to the one running at a lower
frequency, it could badly affect performance for cases like
scrolling.
This change tries to raise the frequency of the destination core
to the same value as the source core, if it is not already running
at the same or higher frequency.  In order for the ondemand
governor to have a fair idea of load in the next sample, it also
reschedules the next sample one sampling interval from the
frequency transition after which the ondemand governor again
takes over.

Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>
Change-Id: I9d2fbb166b0cc042d3fd57cea75a5066df4c794b
cpufreq: Use dedicated high-priority workqueues

In the process of scaling CPU frequencies, cpufreq and the APIS is
calls may hold resources that will prevent threads critical for
system stability from running.

Specifically, thermal-mitigation software may need to respond
quickly to high-temperature conditions and throttle the CPU speed
in an effort to cool down. If the system is already in the middle
of a CPU frequency switch being executed on behalf of a cpufreq
governor, thermal mitigation will be blocked until the scaling
action has completed. If the system is under heave load of medium
or high-priority threads, this may take a long while and the system
may potentially surpass thermal limits in the meantime.

Resolve this by using high priority workqueues for all ondemand
and conservative governor scaling operations.  This will allow them
to complete promptly and release their hold on resources necessary
for maintaining system stability.

Change-Id: I2f56052c131442838036cf4cdd8059f7c09bb805
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>
cpufreq: ondemand: Fix store_powersave_bias() race with hotplug

store_powersave_bias() assumes that CPUs will not be taken offline or
brought online while executing its for_each_online_cpu() loops. Fix
this race by blocking hotplug while executing in these loop.

CRs-Fixed: 494407
Change-Id: I0d5520444ec21a8d9b12fb73c06ac8442449fa85
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>
cpufreq: ondemand: Fix locking in store_powersave_bias

store_powersave_bias() assumes that dbs_info->cur_policy will
not change while it is executing. If it does, memory corruption
can potentially result. Fix this by acquiring the dbs_lock.

Most noticeably, this resolves timer-related list corruptions
encountered when queue_delayed_work_on() is called from within
store_powersave_bias() while a CPU is being hotplugged in and
out.

CRs-Fixed: 494407
Change-Id: I0fd5cbef6834545274cad9481e574ec50b37b871
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>
cpufreq: ondemand: change freq sync code to use per-CPU kthreads

The migration notifier may run in a context where it is not safe to
enqueue a work item. For example:

(__queue_work+0x1f4/0x40c)
(queue_work_on+0x34/0x44)
(dbs_migration_notify+0x2c/0x40)
(notifier_call_chain+0x38/0x68)
(__atomic_notifier_call_chain+0x34/0x44)
(atomic_notifier_call_chain+0x14/0x18)
(try_to_wake_up+0x350/0x36c)
(autoremove_wake_function+0xc/0x34)
(__wake_up_common+0x48/0x7c)
(__wake_up+0x3c/0x50)
(trustee_thread+0x1d0/0x528)
(kthread+0x80/0x8c)

The trustee code already takes a lock internal to the workqueue
implementation and is not expecting a wake up to come around and
enter the workqueue code again, where the same lock will be needed.

Instead of relying on a workqueue, use a per-CPU kthread to do
the frequency syncing.

Change-Id: I7555ee40867792fa8ec4ea8f9a6309323775e797
CRs-Fixed: 501099
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
cpufreq: Avoid using smp_processor_id() in preemptible context

Even though this work item runs on only one cpu at a time (due to
queue_work_on()) it is possible for the work item to be preempted
and so use of smp_processor_id() is illegal.

BUG: using smp_processor_id() in preemptible [00000000]
code: kworker/3:1/4162 caller is dbs_refresh_callback+0xc/0x188
[<c00151b0>] (unwind_backtrace+0x0/0x120) from [<c0279058>]
(debug_smp_processor_id+0xbc/0xf0)
[<c0279058>] (debug_smp_processor_id+0xbc/0xf0) from [<c0454b54>]
(dbs_refresh_callback+0xc/0x188)
[<c0454b54>] (dbs_refresh_callback+0xc/0x188) from [<c0087290>]
(process_one_work+0x354/0x648)
[<c0087290>] (process_one_work+0x354/0x648) from [<c0089754>]
(worker_thread+0x1a8/0x2a8)
[<c0089754>] (worker_thread+0x1a8/0x2a8) from [<c008e480>]
(kthread+0x90/0xa0)
[<c008e480>] (kthread+0x90/0xa0) from [<c000f438>]
(kernel_thread_exit+0x0/0x8)

The intent of the code is to determine which CPU this work item
is running on, which we can easily do by passing that information
in a wrapper struct around the work struct. Do this so we avoid
this problem.

Change-Id: I05ca0ff2b3cbaa239930463ea0760e3e9d75145f
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>