Merge branch 'for-linus' of git://git.linaro.org/people/rmk/linux-arm

Pull ARM updates from Russell King:
 "The major items included in here are:

   - MCPM, multi-cluster power management, part of the infrastructure
     required for ARMs big.LITTLE support.

   - A rework of the ARM KVM code to allow re-use by ARM64.

   - Error handling cleanups of the IS_ERR_OR_NULL() madness and fixes
     of that stuff for arch/arm

   - Preparatory patches for Cortex-M3 support from Uwe Kleine-König.

  There is also a set of three patches in here from Hugh/Catalin to
  address freeing of inappropriate page tables on LPAE.  You already
  have these from akpm, but they were already part of my tree at the
  time he sent them, so unfortunately they'll end up with duplicate
  commits"

* 'for-linus' of git://git.linaro.org/people/rmk/linux-arm: (77 commits)
  ARM: EXYNOS: remove unnecessary use of IS_ERR_VALUE()
  ARM: IMX: remove unnecessary use of IS_ERR_VALUE()
  ARM: OMAP: use consistent error checking
  ARM: cleanup: OMAP hwmod error checking
  ARM: 7709/1: mcpm: Add explicit AFLAGS to support v6/v7 multiplatform kernels
  ARM: 7700/2: Make cpu_init() notrace
  ARM: 7702/1: Set the page table freeing ceiling to TASK_SIZE
  ARM: 7701/1: mm: Allow arch code to control the user page table ceiling
  ARM: 7703/1: Disable preemption in broadcast_tlb*_a15_erratum()
  ARM: mcpm: provide an interface to set the SMP ops at run time
  ARM: mcpm: generic SMP secondary bringup and hotplug support
  ARM: mcpm_head.S: vlock-based first man election
  ARM: mcpm: Add baremetal voting mutexes
  ARM: mcpm: introduce helpers for platform coherency exit/setup
  ARM: mcpm: introduce the CPU/cluster power API
  ARM: multi-cluster PM: secondary kernel entry code
  ARM: cacheflush: add synchronization helpers for mixed cache state accesses
  ARM: cpu hotplug: remove majority of cache flushing from platforms
  ARM: smp: flush L1 cache in cpu_die()
  ARM: tegra: remove tegra specific cpu_disable()
  ...

96 files changed, 3087 insertions, 1210 deletions

diff --git a/Documentation/arm/cluster-pm-race-avoidance.txt b/Documentation/arm/cluster-pm-race-avoidance.txt
new file mode 100644
index 00000000000..750b6fc24af
--- /dev/null
+++ b/Documentation/arm/cluster-pm-race-avoidance.txt
@@ -0,0 +1,498 @@
+Cluster-wide Power-up/power-down race avoidance algorithm
+=========================================================
+
+This file documents the algorithm which is used to coordinate CPU and
+cluster setup and teardown operations and to manage hardware coherency
+controls safely.
+
+The section "Rationale" explains what the algorithm is for and why it is
+needed.  "Basic model" explains general concepts using a simplified view
+of the system.  The other sections explain the actual details of the
+algorithm in use.
+
+
+Rationale
+---------
+
+In a system containing multiple CPUs, it is desirable to have the
+ability to turn off individual CPUs when the system is idle, reducing
+power consumption and thermal dissipation.
+
+In a system containing multiple clusters of CPUs, it is also desirable
+to have the ability to turn off entire clusters.
+
+Turning entire clusters off and on is a risky business, because it
+involves performing potentially destructive operations affecting a group
+of independently running CPUs, while the OS continues to run.  This
+means that we need some coordination in order to ensure that critical
+cluster-level operations are only performed when it is truly safe to do
+so.
+
+Simple locking may not be sufficient to solve this problem, because
+mechanisms like Linux spinlocks may rely on coherency mechanisms which
+are not immediately enabled when a cluster powers up.  Since enabling or
+disabling those mechanisms may itself be a non-atomic operation (such as
+writing some hardware registers and invalidating large caches), other
+methods of coordination are required in order to guarantee safe
+power-down and power-up at the cluster level.
+
+The mechanism presented in this document describes a coherent memory
+based protocol for performing the needed coordination.  It aims to be as
+lightweight as possible, while providing the required safety properties.
+
+
+Basic model
+-----------
+
+Each cluster and CPU is assigned a state, as follows:
+
+	DOWN
+	COMING_UP
+	UP
+	GOING_DOWN
+
+	    +---------> UP ----------+
+	    |                        v
+
+	COMING_UP                GOING_DOWN
+
+	    ^                        |
+	    +--------- DOWN <--------+
+
+
+DOWN:	The CPU or cluster is not coherent, and is either powered off or
+	suspended, or is ready to be powered off or suspended.
+
+COMING_UP: The CPU or cluster has committed to moving to the UP state.
+	It may be part way through the process of initialisation and
+	enabling coherency.
+
+UP:	The CPU or cluster is active and coherent at the hardware
+	level.  A CPU in this state is not necessarily being used
+	actively by the kernel.
+
+GOING_DOWN: The CPU or cluster has committed to moving to the DOWN
+	state.  It may be part way through the process of teardown and
+	coherency exit.
+
+
+Each CPU has one of these states assigned to it at any point in time.
+The CPU states are described in the "CPU state" section, below.
+
+Each cluster is also assigned a state, but it is necessary to split the
+state value into two parts (the "cluster" state and "inbound" state) and
+to introduce additional states in order to avoid races between different
+CPUs in the cluster simultaneously modifying the state.  The cluster-
+level states are described in the "Cluster state" section.
+
+To help distinguish the CPU states from cluster states in this
+discussion, the state names are given a CPU_ prefix for the CPU states,
+and a CLUSTER_ or INBOUND_ prefix for the cluster states.
+
+
+CPU state
+---------
+
+In this algorithm, each individual core in a multi-core processor is
+referred to as a "CPU".  CPUs are assumed to be single-threaded:
+therefore, a CPU can only be doing one thing at a single point in time.
+
+This means that CPUs fit the basic model closely.
+
+The algorithm defines the following states for each CPU in the system:
+
+	CPU_DOWN
+	CPU_COMING_UP
+	CPU_UP
+	CPU_GOING_DOWN
+
+	 cluster setup and
+	CPU setup complete          policy decision
+	      +-----------> CPU_UP ------------+
+	      |                                v
+
+	CPU_COMING_UP                   CPU_GOING_DOWN
+
+	      ^                                |
+	      +----------- CPU_DOWN <----------+
+	 policy decision           CPU teardown complete
+	or hardware event
+
+
+The definitions of the four states correspond closely to the states of
+the basic model.
+
+Transitions between states occur as follows.
+
+A trigger event (spontaneous) means that the CPU can transition to the
+next state as a result of making local progress only, with no
+requirement for any external event to happen.
+
+
+CPU_DOWN:
+
+	A CPU reaches the CPU_DOWN state when it is ready for
+	power-down.  On reaching this state, the CPU will typically
+	power itself down or suspend itself, via a WFI instruction or a
+	firmware call.
+
+	Next state:	CPU_COMING_UP
+	Conditions:	none
+
+	Trigger events:
+
+		a) an explicit hardware power-up operation, resulting
+		   from a policy decision on another CPU;
+
+		b) a hardware event, such as an interrupt.
+
+
+CPU_COMING_UP:
+
+	A CPU cannot start participating in hardware coherency until the
+	cluster is set up and coherent.  If the cluster is not ready,
+	then the CPU will wait in the CPU_COMING_UP state until the
+	cluster has been set up.
+
+	Next state:	CPU_UP
+	Conditions:	The CPU's parent cluster must be in CLUSTER_UP.
+	Trigger events:	Transition of the parent cluster to CLUSTER_UP.
+
+	Refer to the "Cluster state" section for a description of the
+	CLUSTER_UP state.
+
+
+CPU_UP:
+	When a CPU reaches the CPU_UP state, it is safe for the CPU to
+	start participating in local coherency.
+
+	This is done by jumping to the kernel's CPU resume code.
+
+	Note that the definition of this state is slightly different
+	from the basic model definition: CPU_UP does not mean that the
+	CPU is coherent yet, but it does mean that it is safe to resume
+	the kernel.  The kernel handles the rest of the resume
+	procedure, so the remaining steps are not visible as part of the
+	race avoidance algorithm.
+
+	The CPU remains in this state until an explicit policy decision
+	is made to shut down or suspend the CPU.
+
+	Next state:	CPU_GOING_DOWN
+	Conditions:	none
+	Trigger events:	explicit policy decision
+
+
+CPU_GOING_DOWN:
+
+	While in this state, the CPU exits coherency, including any
+	operations required to achieve this (such as cleaning data
+	caches).
+
+	Next state:	CPU_DOWN
+	Conditions:	local CPU teardown complete
+	Trigger events:	(spontaneous)
+
+
+Cluster state
+-------------
+
+A cluster is a group of connected CPUs with some common resources.
+Because a cluster contains multiple CPUs, it can be doing multiple
+things at the same time.  This has some implications.  In particular, a
+CPU can start up while another CPU is tearing the cluster down.
+
+In this discussion, the "outbound side" is the view of the cluster state
+as seen by a CPU tearing the cluster down.  The "inbound side" is the
+view of the cluster state as seen by a CPU setting the CPU up.
+
+In order to enable safe coordination in such situations, it is important
+that a CPU which is setting up the cluster can advertise its state
+independently of the CPU which is tearing down the cluster.  For this
+reason, the cluster state is split into two parts:
+
+	"cluster" state: The global state of the cluster; or the state
+		on the outbound side:
+
+		CLUSTER_DOWN
+		CLUSTER_UP
+		CLUSTER_GOING_DOWN
+
+	"inbound" state: The state of the cluster on the inbound side.
+
+		INBOUND_NOT_COMING_UP
+		INBOUND_COMING_UP
+
+
+	The different pairings of these states results in six possible
+	states for the cluster as a whole:
+
+	                            CLUSTER_UP
+	          +==========> INBOUND_NOT_COMING_UP -------------+
+	          #                                               |
+	                                                          |
+	     CLUSTER_UP     <----+                                |
+	  INBOUND_COMING_UP      |                                v
+
+	          ^             CLUSTER_GOING_DOWN       CLUSTER_GOING_DOWN
+	          #              INBOUND_COMING_UP <=== INBOUND_NOT_COMING_UP
+
+	    CLUSTER_DOWN         |                                |
+	  INBOUND_COMING_UP <----+                                |
+	                                                          |
+	          ^                                               |
+	          +===========     CLUSTER_DOWN      <------------+
+	                       INBOUND_NOT_COMING_UP
+
+	Transitions -----> can only be made by the outbound CPU, and
+	only involve changes to the "cluster" state.
+
+	Transitions ===##> can only be made by the inbound CPU, and only
+	involve changes to the "inbound" state, except where there is no
+	further transition possible on the outbound side (i.e., the
+	outbound CPU has put the cluster into the CLUSTER_DOWN state).
+
+	The race avoidance algorithm does not provide a way to determine
+	which exact CPUs within the cluster play these roles.  This must
+	be decided in advance by some other means.  Refer to the section
+	"Last man and first man selection" for more explanation.
+
+
+	CLUSTER_DOWN/INBOUND_NOT_COMING_UP is the only state where the
+	cluster can actually be powered down.
+
+	The parallelism of the inbound and outbound CPUs is observed by
+	the existence of two different paths from CLUSTER_GOING_DOWN/
+	INBOUND_NOT_COMING_UP (corresponding to GOING_DOWN in the basic
+	model) to CLUSTER_DOWN/INBOUND_COMING_UP (corresponding to
+	COMING_UP in the basic model).  The second path avoids cluster
+	teardown completely.
+
+	CLUSTER_UP/INBOUND_COMING_UP is equivalent to UP in the basic
+	model.  The final transition to CLUSTER_UP/INBOUND_NOT_COMING_UP
+	is trivial and merely resets the state machine ready for the
+	next cycle.
+
+	Details of the allowable transitions follow.
+
+	The next state in each case is notated
+<