cpuidle: refactor out cpuidle_enter_state

Split the code to enter a state and update the stats into a helper
function, cpuidle_enter_state, and export it.  This function will
be called by the coupled state code to handle entering the safe
state and the final coupled state.

Change-Id: I7b18848370c61408de5960e3844e8faf426fa575
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Colin Cross <ccross@android.com>
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
cpuidle: fix error handling in __cpuidle_register_device

Fix the error handling in __cpuidle_register_device to include
the missing list_del.  Move it to a label, which will simplify
the error handling when coupled states are added.

Change-Id: I1e0fcbf97e9542c3f5f7634ef9bfc126d518d51e
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Colin Cross <ccross@android.com>
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
cpuidle: add support for states that affect multiple cpus

On some ARM SMP SoCs (OMAP4460, Tegra 2, and probably more), the
cpus cannot be independently powered down, either due to
sequencing restrictions (on Tegra 2, cpu 0 must be the last to
power down), or due to HW bugs (on OMAP4460, a cpu powering up
will corrupt the gic state unless the other cpu runs a work
around).  Each cpu has a power state that it can enter without
coordinating with the other cpu (usually Wait For Interrupt, or
WFI), and one or more "coupled" power states that affect blocks
shared between the cpus (L2 cache, interrupt controller, and
sometimes the whole SoC).  Entering a coupled power state must
be tightly controlled on both cpus.

The easiest solution to implementing coupled cpu power states is
to hotplug all but one cpu whenever possible, usually using a
cpufreq governor that looks at cpu load to determine when to
enable the secondary cpus.  This causes problems, as hotplug is an
expensive operation, so the number of hotplug transitions must be
minimized, leading to very slow response to loads, often on the
order of seconds.

This file implements an alternative solution, where each cpu will
wait in the WFI state until all cpus are ready to enter a coupled
state, at which point the coupled state function will be called
on all cpus at approximately the same time.

Once all cpus are ready to enter idle, they are woken by an smp
cross call.  At this point, there is a chance that one of the
cpus will find work to do, and choose not to enter idle.  A
final pass is needed to guarantee that all cpus will call the
power state enter function at the same time.  During this pass,
each cpu will increment the ready counter, and continue once the
ready counter matches the number of online coupled cpus.  If any
cpu exits idle, the other cpus will decrement their counter and
retry.

To use coupled cpuidle states, a cpuidle driver must:

   Set struct cpuidle_device.coupled_cpus to the mask of all
   coupled cpus, usually the same as cpu_possible_mask if all cpus
   are part of the same cluster.  The coupled_cpus mask must be
   set in the struct cpuidle_device for each cpu.

   Set struct cpuidle_device.safe_state to a state that is not a
   coupled state.  This is usually WFI.

   Set CPUIDLE_FLAG_COUPLED in struct cpuidle_state.flags for each
   state that affects multiple cpus.

   Provide a struct cpuidle_state.enter function for each state
   that affects multiple cpus.  This function is guaranteed to be
   called on all cpus at approximately the same time.  The driver
   should ensure that the cpus all abort together if any cpu tries
   to abort once the function is called.

update1:

cpuidle: coupled: fix count of online cpus

online_count was never incremented on boot, and was also counting
cpus that were not part of the coupled set.  Fix both issues by
introducting a new function that counts online coupled cpus, and
call it from register as well as the hotplug notifier.

update2:

cpuidle: coupled: fix decrementing ready count

cpuidle_coupled_set_not_ready sometimes refuses to decrement the
ready count in order to prevent a race condition.  This makes it
unsuitable for use when finished with idle.  Add a new function
cpuidle_coupled_set_done that decrements both the ready count and
waiting count, and call it after idle is complete.

Change-Id: If304c55c17c4aadd693f843d941fb0e6c3375ac0
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Trinabh Gupta <g.trinabh@gmail.com>
Cc: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Colin Cross <ccross@android.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
block: Adding ROW scheduling algorithm

This patch adds the implementation of a new scheduling algorithm - ROW.
The policy of this algorithm is to prioritize READ requests over WRITE
as much as possible without starving the WRITE requests.

Change-Id: I4ed52ea21d43b0e7c0769b2599779a3d3869c519
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: ROW: Correct minimum values of ROW tunable parameters

The ROW scheduling algorithm exposes several tunable parameters.
This patch updates the minimum allowed values for those parameters.

Change-Id: I5ec19d54b694e2e83ad5376bd99cc91f084967f5
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: ROW: Fix forced dispatch

This patch fixes forced dispatch in the ROW scheduling algorithm.
When the dispatch function is called with the forced flag on, we
can't delay the dispatch of the requests that are in scheduler queues.
Thus, when dispatch is called with forced turned on, we need to cancel
idling, or not to idle at all.

Change-Id: I3aa0da33ad7b59c0731c696f1392b48525b52ddc
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: Add support for reinsert a dispatched req

Add support for reinserting a dispatched request back to the
scheduler's internal data structures.
This capability is used by the device driver when it chooses to
interrupt the current request transmission and execute another (more
urgent) pending request. For example: interrupting long write in order
to handle pending read. The device driver re-inserts the
remaining write request back to the scheduler, to be rescheduled
for transmission later on.

Add API for verifying whether the current scheduler
supports reinserting requests mechanism. If reinsert mechanism isn't
supported by the scheduler, this code path will never be activated.

Change-Id: I5c982a66b651ebf544aae60063ac8a340d79e67f
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: Add API for urgent request handling

This patch add support in block & elevator layers for handling
urgent requests. The decision if a request is urgent or not is taken
by the scheduler. Urgent request notification is passed to the underlying
block device driver (eMMC for example). Block device driver may decide to
interrupt the currently running low priority request to serve the new
urgent request. By doing so READ latency is greatly reduced in read&write
collision scenarios.

Note that if the current scheduler doesn't implement the urgent request
mechanism, this code path is never activated.

Change-Id: I8aa74b9b45c0d3a2221bd4e82ea76eb4103e7cfa
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
row: Adding support for reinsert already dispatched req

Add support for reinserting already dispatched request back to the
schedulers internal data structures.
The request will be reinserted back to the queue (head) it was
dispatched from as if it was never dispatched.

Change-Id: I70954df300774409c25b5821465fb3aa33d8feb5
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block:row: fix idling mechanism in ROW

This patch addresses the following issues found in the ROW idling
mechanism:
1. Fix the delay passed to queue_delayed_work (pass actual delay
   and not the time when to start the work)
2. Change the idle time and the idling-trigger frequency to be
   HZ dependent (instead of using msec_to_jiffies())
3. Destroy idle_workqueue() in queue_exit

Change-Id: If86513ad6b4be44fb7a860f29bd2127197d8d5bf
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
row: Add support for urgent request handling

This patch adds support for handling urgent requests.
ROW queue can be marked as "urgent" so if it was un-served in last
dispatch cycle and a request was added to it - it will trigger
issuing an urgent-request-notification to the block device driver.
The block device driver may choose at stop the transmission of current
ongoing request to handle the urgent one. Foe example: long WRITE may
be stopped to handle an urgent READ. This decreases READ latency.

Change-Id: I84954c13f5e3b1b5caeadc9fe1f9aa21208cb35e
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Add some debug information on ROW queues

1. Add a counter for number of requests on queue.
2. Add function to print queues status (number requests
   currently on queue and number of already dispatched requests
   in current dispatch cycle).

Change-Id: I1e98b9ca33853e6e6a8ddc53240f6cd6981e6024
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Insert dispatch_quantum into struct row_queue

There is really no point in keeping the dispatch quantum
of a queue outside of it. By inserting it to the row_queue
structure we spare extra level in accessing it.

Change-Id: Ic77571818b643e71f9aafbb2ca93d0a92158b199
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: fix sysfs functions - idle_time conversion

idle_time was updated to be stored in msec instead of jiffies.
So there is no need to convert the value when reading from user or
displaying the value to him.

Change-Id: I58e074b204e90a90536d32199ac668112966e9cf
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Aggregate row_queue parameters to one structure

Each ROW queues has several parameters which default values are defined
in separate arrays. This patch aggregates all default values into one
array.
The values in question are:
 - is idling enabled for the queue
 - queue quantum
 - can the queue notify on urgent request

Change-Id: I3821b0a042542295069b340406a16b1000873ec6
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Dispatch requests according to their io-priority

This patch implements "application-hints" which is a way the issuing
application can notify the scheduler on the priority of its request.
This is done by setting the io-priority of the request.
This patch reuses an already existing mechanism of io-priorities developed
for CFQ. Please refer to kernel/Documentation/block/ioprio.txt for
usage example and explanations.

Change-Id: I228ec8e52161b424242bb7bb133418dc8b73925a
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Idling mechanism re-factoring

At the moment idling in ROW is implemented by delayed work that uses
jiffies granularity which is not very accurate. This patch replaces
current idling mechanism implementation with hrtime API, which gives
nanosecond resolution (instead of jiffies).

Change-Id: I86c7b1776d035e1d81571894b300228c8b8f2d92
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Don't notify URGENT if there are un-completed urgent req

When ROW scheduler reports to the block layer that there is an urgent
request pending, the device driver may decide to stop the transmission
of the current request in order to handle the urgent one. If the current
transmitted request is an urgent request - we don't want it to be
stopped.
Due to the above ROW scheduler won't notify of an urgent request if
there are urgent requests in flight.

Change-Id: I2fa186d911b908ec7611682b378b9cdc48637ac7
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Update initial values of ROW data structures

This patch sets the initial values of internal ROW
parameters.

Change-Id: I38132062a7fcbe2e58b9cc757e55caac64d013dc
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
[smuckle@codeaurora.org: ported from msm-3.7]
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
block: row: Re-design urgent request notification mechanism

This patch updates the ROW URGENT notification policy to apply with the
bellow:
- Don't notify URGENT if there is an un-completed URGENT request in driver
- After notifying that URGENT request is present, the next request
  dispatched is the URGENT one.
- At every given moment only 1 request can be marked as URGENT.
  Independent of it's location (driver or scheduler)

Other changes to URGENT policy:
- Only queues that are allowed to notify of an URGENT request pending
are READ queues

Change-Id: I17ff73125bc7a760cea1116b466115a2df635a14
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>