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>
cpufreq: ondemand: Fix kernel warning in cpufreq_governor_dbs

GOV_STOP event destroys the timer_mutex and is not initialized back
upon GOV_START event.
The Kernel complains at mutex_lock(during GOV_LIMITS event) after
mutex_destroy.

[<c0014918>] (unwind_backtrace+0x0/0x11c)
[<c007c004>] (warn_slowpath_common+0x4c/0x64)
[<c007c034>] (warn_slowpath_null+0x18/0x1c)
[<c079eef8>] (__mutex_lock_slowpath+0x130/0x3c4)
[<c079f1ac>] (mutex_lock+0x20/0x3c) from [<c0540900>]
[<c0540900>] (cpufreq_governor_dbs+0x3c8/0x468)
[<c053d500>] (__cpufreq_governor+0x90/0xe0)
[<c053d774>] (__cpufreq_set_policy+0x224/0x258)
[<c053da58>] (cpufreq_add_dev_interface+0x2b0/0x308)
[<c053e784>] (cpufreq_add_dev+0x500/0x56c)
[<c079247c>] (cpufreq_cpu_callback+0x88/0x9c)
[<c07a2ca8>] (notifier_call_chain+0x38/0x68)
[<c007ded0>] (__cpu_notify+0x28/0x40)
[<c0790024>] (_cpu_up+0xe4/0x118)
[<c0790024>] (cpu_up+0x64/0x80)
[<c0765840>] (store_online+0x48/0x78)
[<c038d0c8>] (dev_attr_store+0x18/0x24)
[<c017be40>] (sysfs_write_file+0x108/0x13c)
[<c012cdfc>] (vfs_write+0xb0/0x128)
[<c012d034>](sys_write+0x38/0x64)

Change-Id: Ie2a796b17209243de731ccf2ab04b7f9e7048df8
Signed-off-by: Anji Jonnala <anjir@codeaurora.org>
msm: cpufreq: make the gov stop part fully atomic

In the function cpufreq_governor_dbs, the case CPUFREQ_GOV_STOP
is not completely atomic. The removal of sysfs is outside the
critical path. If a START/STOP done frequently from user space
then there is chance of adding the sysfs interface before removal.
This creates a warning from sysfs saying creating an already
existing entry.

Also once it fails to create, cpufreq_governor_dbs returns with
error code. The dbs_enable value is incremented which is not
rolled back and cpufreq core tries to set the old
governor. This might create further problems.

Hence the removal of sysfs entry should happen in the critical
path.

CRs-fixed: 440969
Change-Id: I98891756caf2ce0b85e39e9b4f58034af1ed97ce
Signed-off-by: Venkat Devarasetty <vdevaras@codeaurora.org>
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: 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: Disable freq sync feature in store_powersave_bias

Turn off frequency synchronization of CPUs on thread migrations
when powersave bias is enabled. This is done to prevent re-arming
of the dbs timer work (which is cancelled by store_powersave_bias)
by the sync_thread.

Change-Id: I165dd591845c1d66d01a14e8dfc44c767c677b0d
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>
cpufreq: ondemand: Boost CPU frequency only for touch input

Originally CPU frequency were boosted for any input event.
In some case, sensor sends a lot of input event, which
keep CPU in high frequency.  CPU frequency only need to
be boosted when real user interaction happens.

Change-Id: Ia3ad755b98d8363a17729926610b5dd6f0075288
CR-Fixed: 507519
Signed-off-by: Tingwei Zhang <tingwei@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>
cpufreq: ondemand: fix timer-related list corruption in store_powersave_bias()

The dbs_timer_init() call in store_powersave_bias() re-initializes the
dbs_info workqueue, call on dbs_timer_exit() to ensure
outstanding work is cleared prior to making this call. Also, grab the
percpu timer_mutex lock to avoid race conditions with respect to the
dbs timer.

Change-Id: I79f3d43eeb51d2d8e21edd0fe043d6583333951f
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>
ondemand: add sysfs entry for down_diff_multi_core

This change adds sysfs entry for the ondemand governor's attribute
down_differential_multi_core. This is required to be able to program
this knob to attain better perf/power for use cases like camcorder.

CRs-fixed: 561456
Change-Id: Ib7c1223215c6b714c286c231ed37f3abfae741c6
Signed-off-by: Krishna Vanka <kvanka@codeaurora.org>
cpufreq: ondemand: Remove unnecessary synchronization attempt

Commit 1ce28d6b (ondemand: updated tune for hardware coordination)
brings in an attempt to synchronize expiry of per-cpu ondemand timer
at same time across all online cpus. This is meant to help systems
where "multiple cores share P-state via Hardware Coordination".

Synchronization is achieved by having timers expire when jiffy value
would be a perfect multiple of sampling window size. While such
synchronozation attemps are unnecessary on systems where cores don't
share P-states, it can hurt on power as cpus can now work off shorter
sampling windows (when percentage utilization over short window can be
observed to be high, causing frequency to be boosted).

Remove this unnecessary attempt to synchronize expiry of ondemand
timer across online cpus. A more acceptable solution could be to have
low-level architecture specific cpufreq driver indicate the need for
synchronization.

Change-Id: I6cb1cf3472ca106f029dc01248e0df7cfbb495b8
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>