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>
Signed-off-by: Ajay Dudani <adudani@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
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
Signed-off-by: Ajay Dudani <adudani@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: Fix locking issue in store_powersave_bias

store_powersave_bias takes timer_mutex before calling dbs_timer_exit
which tries to cancel the delayed work do_dbs_timer which in turn
tries to take the same lock. This can cause a lock recursion under
the race condition where can cancel_delayed_work_sync is called
when the work has already started executing.

This can be avoided by taking that lock after calling
dbs_timer_exit.

Change-Id: I7f862286e66f1ddc1e13e4eeee369dd188fc10d5
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>
cpufreq: ondemand: Fix update_sampling_rate race with hotplug

update_sampling_rate has a for loop which goes through each
online cpu and possibly queue up the ondemand work for them.
But while doing this it doesnt take any hotplug lock which
could potentially cause a race condition where ondemand work
is queued after the hotplug code (which sets the policy to NULL)
in the governor has cancelled any pending work. This could cause
a crash while trying to access the NULL policy in dbs_check_cpu.

Protecting the for_each_online_cpu loop with get_online_cpus()
and put_online_cpus().

Change-Id: Ia3f43ca7e4bed542834ab03ca1191d728f13311c
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>
cpufreq: ondemand: Fix hotplug deadlock with store_powersave_bias

store_powersave_bias() acquires the hotplug lock and the dbs_mutex
lock, but does so in the wrong order.  Deadlocks like the following
can result.

Thread A:
    get_online_cpus+0x3c/0x5c           <- acquires 'cpu_hotplug.lock'
    store_powersave_bias+0x80/0x3f4     <- acquires 'dbs_mutex'
    kobj_attr_store+0x14/0x20
    sysfs_write_file+0x108/0x13c
    vfs_write+0xb0/0x128
    sys_write+0x38/0x64

Thread B:
    cpufreq_governor_dbs+0x7c/0x55c     <- acquires 'dbs_mutex'
    __cpufreq_governor+0x90/0xe0
    __cpufreq_set_policy+0x1b0/0x258
    cpufreq_add_dev_interface+0x2cc/0x334
    cpufreq_add_dev+0x514/0x580
    cpufreq_cpu_callback+0x88/0x9c
    notifier_call_chain+0x38/0x68
    __cpu_notify+0x28/0x40
    _cpu_up+0xe4/0x118                  <- acquires 'cpu_hotplug.lock'
    cpu_up+0x64/0x80
    store_online+0x48/0x78
    dev_attr_store+0x18/0x24
    sysfs_write_file+0x108/0x13c
    vfs_write+0xb0/0x128
    sys_write+0x38/0x64

Fix this by flipping the order in which the locks are acquired and
released in store_powersave_bias so that it is the same as in the
hotplug path.

Change-Id: Idc59fb29d60b8f7fceb8ed0f2bb9eff4670abda7
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>
cpufreq: ondemand: add input_boost interface

Currently Ondemand governor handles any input event
like touch by scaling the CPU frequency to maximum
available on the target.

This change adds a new sysfs interface "input_boost"
whereby the CPU will scale to this frequency on input events.
The value of this sysfs is user defined so input events
can now be handled by scaling the CPU to lower frequencies
than target max.

Change-Id: I5428fd8797c9984b17a66b01a44557f2160e8b68
Signed-off-by: Dilip Gudlur <dgudlur@codeaurora.org>