Merge 3.10-rc3 into char-misc-next

We want the changes in here.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

15 files changed, 419 insertions, 39 deletions

diff --git a/Documentation/devicetree/bindings/net/macb.txt b/Documentation/devicetree/bindings/net/macb.txt
index 44afa0e5057d..4ff65047bb9a 100644
--- a/Documentation/devicetree/bindings/net/macb.txt
+++ b/Documentation/devicetree/bindings/net/macb.txt
@@ -4,7 +4,7 @@ Required properties:
 - compatible: Should be "cdns,[<chip>-]{macb|gem}"
   Use "cdns,at91sam9260-macb" Atmel at91sam9260 and at91sam9263 SoCs.
   Use "cdns,at32ap7000-macb" for other 10/100 usage or use the generic form: "cdns,macb".
-  Use "cnds,pc302-gem" for Picochip picoXcell pc302 and later devices based on
+  Use "cdns,pc302-gem" for Picochip picoXcell pc302 and later devices based on
   the Cadence GEM, or the generic form: "cdns,gem".
 - reg: Address and length of the register set for the device
 - interrupts: Should contain macb interrupt
diff --git a/Documentation/devicetree/bindings/drm/exynos/hdmi.txt b/Documentation/devicetree/bindings/video/exynos_hdmi.txt
index 589edee37394..589edee37394 100644
--- a/Documentation/devicetree/bindings/drm/exynos/hdmi.txt
+++ b/Documentation/devicetree/bindings/video/exynos_hdmi.txt
diff --git a/Documentation/devicetree/bindings/drm/exynos/hdmiddc.txt b/Documentation/devicetree/bindings/video/exynos_hdmiddc.txt
index fa166d945809..fa166d945809 100644
--- a/Documentation/devicetree/bindings/drm/exynos/hdmiddc.txt
+++ b/Documentation/devicetree/bindings/video/exynos_hdmiddc.txt
diff --git a/Documentation/devicetree/bindings/drm/exynos/hdmiphy.txt b/Documentation/devicetree/bindings/video/exynos_hdmiphy.txt
index 858f4f9b902f..858f4f9b902f 100644
--- a/Documentation/devicetree/bindings/drm/exynos/hdmiphy.txt
+++ b/Documentation/devicetree/bindings/video/exynos_hdmiphy.txt
diff --git a/Documentation/devicetree/bindings/drm/exynos/mixer.txt b/Documentation/devicetree/bindings/video/exynos_mixer.txt
index 9b2ea0343566..9b2ea0343566 100644
--- a/Documentation/devicetree/bindings/drm/exynos/mixer.txt
+++ b/Documentation/devicetree/bindings/video/exynos_mixer.txt
diff --git a/Documentation/devicetree/bindings/video/simple-framebuffer.txt b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
new file mode 100644
index 000000000000..3ea460583111
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
@@ -0,0 +1,25 @@
+Simple Framebuffer
+
+A simple frame-buffer describes a raw memory region that may be rendered to,
+with the assumption that the display hardware has already been set up to scan
+out from that buffer.
+
+Required properties:
+- compatible: "simple-framebuffer"
+- reg: Should contain the location and size of the framebuffer memory.
+- width: The width of the framebuffer in pixels.
+- height: The height of the framebuffer in pixels.
+- stride: The number of bytes in each line of the framebuffer.
+- format: The format of the framebuffer surface. Valid values are:
+  - r5g6b5 (16-bit pixels, d[15:11]=r, d[10:5]=g, d[4:0]=b).
+
+Example:
+
+        framebuffer {
+                compatible = "simple-framebuffer";
+                reg = <0x1d385000 (1600 * 1200 * 2)>;
+                width = <1600>;
+                height = <1200>;
+                stride = <(1600 * 2)>;
+                format = "r5g6b5";
+        };
diff --git a/Documentation/devicetree/usage-model.txt b/Documentation/devicetree/usage-model.txt
index ef9d06c9f8fd..0efedaad5165 100644
--- a/Documentation/devicetree/usage-model.txt
+++ b/Documentation/devicetree/usage-model.txt
@@ -191,9 +191,11 @@ Linux it will look something like this:
         };
 
 The bootargs property contains the kernel arguments, and the initrd-*
-properties define the address and size of an initrd blob.  The
-chosen node may also optionally contain an arbitrary number of
-additional properties for platform-specific configuration data.
+properties define the address and size of an initrd blob.  Note that
+initrd-end is the first address after the initrd image, so this doesn't
+match the usual semantic of struct resource.  The chosen node may also
+optionally contain an arbitrary number of additional properties for
+platform-specific configuration data.
 
 During early boot, the architecture setup code calls of_scan_flat_dt()
 several times with different helper callbacks to parse device tree
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index c3bfacb92910..6e3b18a8afc6 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3005,6 +3005,27 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         Force threading of all interrupt handlers except those
                         marked explicitly IRQF_NO_THREAD.
 
+        tmem            [KNL,XEN]
+                        Enable the Transcendent memory driver if built-in.
+
+        tmem.cleancache=0|1 [KNL, XEN]
+                        Default is on (1). Disable the usage of the cleancache
+                        API to send anonymous pages to the hypervisor.
+
+        tmem.frontswap=0|1 [KNL, XEN]
+                        Default is on (1). Disable the usage of the frontswap
+                        API to send swap pages to the hypervisor. If disabled
+                        the selfballooning and selfshrinking are force disabled.
+
+        tmem.selfballooning=0|1 [KNL, XEN]
+                        Default is on (1). Disable the driving of swap pages
+                        to the hypervisor.
+
+        tmem.selfshrinking=0|1 [KNL, XEN]
+                        Default is on (1). Partial swapoff that immediately
+                        transfers pages from Xen hypervisor back to the
+                        kernel based on different criteria.
+
         topology=       [S390]
                         Format: {off | on}
                         Specify if the kernel should make use of the cpu
diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt
new file mode 100644
index 000000000000..cbf7ae412da4
--- /dev/null
+++ b/Documentation/kernel-per-CPU-kthreads.txt
@@ -0,0 +1,202 @@
+REDUCING OS JITTER DUE TO PER-CPU KTHREADS
+
+This document lists per-CPU kthreads in the Linux kernel and presents
+options to control their OS jitter.  Note that non-per-CPU kthreads are
+not listed here.  To reduce OS jitter from non-per-CPU kthreads, bind
+them to a "housekeeping" CPU dedicated to such work.
+
+
+REFERENCES
+
+o       Documentation/IRQ-affinity.txt:  Binding interrupts to sets of CPUs.
+
+o       Documentation/cgroups:  Using cgroups to bind tasks to sets of CPUs.
+
+o       man taskset:  Using the taskset command to bind tasks to sets
+        of CPUs.
+
+o       man sched_setaffinity:  Using the sched_setaffinity() system
+        call to bind tasks to sets of CPUs.
+
+o       /sys/devices/system/cpu/cpuN/online:  Control CPU N's hotplug state,
+        writing "0" to offline and "1" to online.
+
+o       In order to locate kernel-generated OS jitter on CPU N:
+
+                cd /sys/kernel/debug/tracing
+                echo 1 > max_graph_depth # Increase the "1" for more detail
+                echo function_graph > current_tracer
+                # run workload
+                cat per_cpu/cpuN/trace
+
+
+KTHREADS
+
+Name: ehca_comp/%u
+Purpose: Periodically process Infiniband-related work.
+To reduce its OS jitter, do any of the following:
+1.      Don't use eHCA Infiniband hardware, instead choosing hardware
+        that does not require per-CPU kthreads.  This will prevent these
+        kthreads from being created in the first place.  (This will
+        work for most people, as this hardware, though important, is
+        relatively old and is produced in relatively low unit volumes.)
+2.      Do all eHCA-Infiniband-related work on other CPUs, including
+        interrupts.
+3.      Rework the eHCA driver so that its per-CPU kthreads are
+        provisioned only on selected CPUs.
+
+
+Name: irq/%d-%s
+Purpose: Handle threaded interrupts.
+To reduce its OS jitter, do the following:
+1.      Use irq affinity to force the irq threads to execute on
+        some other CPU.
+
+Name: kcmtpd_ctr_%d
+Purpose: Handle Bluetooth work.
+To reduce its OS jitter, do one of the following:
+1.      Don't use Bluetooth, in which case these kthreads won't be
+        created in the first place.
+2.      Use irq affinity to force Bluetooth-related interrupts to
+        occur on some other CPU and furthermore initiate all
+        Bluetooth activity on some other CPU.
+
+Name: ksoftirqd/%u
+Purpose: Execute softirq handlers when threaded or when under heavy load.
+To reduce its OS jitter, each softirq vector must be handled
+separately as follows:
+TIMER_SOFTIRQ:  Do all of the following:
+1.      To the extent possible, keep the CPU out of the kernel when it
+        is non-idle, for example, by avoiding system calls and by forcing
+        both kernel threads and interrupts to execute elsewhere.
+2.      Build with CONFIG_HOTPLUG_CPU=y.  After boot completes, force
+        the CPU offline, then bring it back online.  This forces
+        recurring timers to migrate elsewhere.  If you are concerned
+        with multiple CPUs, force them all offline before bringing the
+        first one back online.  Once you have onlined the CPUs in question,
+        do not offline any other CPUs, because doing so could force the
+        timer back onto one of the CPUs in question.
+NET_TX_SOFTIRQ and NET_RX_SOFTIRQ:  Do all of the following:
+1.      Force networking interrupts onto other CPUs.
+2.      Initiate any network I/O on other CPUs.
+3.      Once your application has started, prevent CPU-hotplug operations
+        from being initiated from tasks that might run on the CPU to
+        be de-jittered.  (It is OK to force this CPU offline and then
+        bring it back online before you start your application.)
+BLOCK_SOFTIRQ:  Do all of the following:
+1.      Force block-device interrupts onto some other CPU.
+2.      Initiate any block I/O on other CPUs.
+3.      Once your application has started, prevent CPU-hotplug operations
+        from being initiated from tasks that might run on the CPU to
+        be de-jittered.  (It is OK to force this CPU offline and then
+        bring it back online before you start your application.)
+BLOCK_IOPOLL_SOFTIRQ:  Do all of the following:
+1.      Force block-device interrupts onto some other CPU.
+2.      Initiate any block I/O and block-I/O polling on other CPUs.
+3.      Once your application has started, prevent CPU-hotplug operations
+        from being initiated from tasks that might run on the CPU to
+        be de-jittered.  (It is OK to force this CPU offline and then
+        bring it back online before you start your application.)
+TASKLET_SOFTIRQ: Do one or more of the following:
+1.      Avoid use of drivers that use tasklets.  (Such drivers will contain
+        calls to things like tasklet_schedule().)
+2.      Convert all drivers that you must use from tasklets to workqueues.
+3.      Force interrupts for drivers using tasklets onto other CPUs,
+        and also do I/O involving these drivers on other CPUs.
+SCHED_SOFTIRQ: Do all of the following:
+1.      Avoid sending scheduler IPIs to the CPU to be de-jittered,
+        for example, ensure that at most one runnable kthread is present
+        on that CPU.  If a thread that expects to run on the de-jittered
+        CPU awakens, the scheduler will send an IPI that can result in
+        a subsequent SCHED_SOFTIRQ.
+2.      Build with CONFIG_RCU_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_ALL=y,
+        CONFIG_NO_HZ_FULL=y, and, in addition, ensure that the CPU
+        to be de-jittered is marked as an adaptive-ticks CPU using the
+        "nohz_full=" boot parameter.  This reduces the number of
+        scheduler-clock interrupts that the de-jittered CPU receives,
+        minimizing its chances of being selected to do the load balancing
+        work that runs in SCHED_SOFTIRQ context.
+3.      To the extent possible, keep the CPU out of the kernel when it
+        is non-idle, for example, by avoiding system calls and by
+        forcing both kernel threads and interrupts to execute elsewhere.
+        This further reduces the number of scheduler-clock interrupts
+        received by the de-jittered CPU.
+HRTIMER_SOFTIRQ:  Do all of the following:
+1.      To the extent possible, keep the CPU out of the kernel when it
+        is non-idle.  For example, avoid system calls and force both
+        kernel threads and interrupts to execute elsewhere.
+2.      Build with CONFIG_HOTPLUG_CPU=y.  Once boot completes, force the
+        CPU offline, then bring it back online.  This forces recurring
+        timers to migrate elsewhere.  If you are concerned with multiple
+        CPUs, force them all offline before bringing the first one
+        back online.  Once you have onlined the CPUs in question, do not
+        offline any other CPUs, because doing so could force the timer
+        back onto one of the CPUs in question.
+RCU_SOFTIRQ:  Do at least one of the following:
+1.      Offload callbacks and keep the CPU in either dyntick-idle or
+        adaptive-ticks state by doing all of the following:
+        a.      Build with CONFIG_RCU_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_ALL=y,
+                CONFIG_NO_HZ_FULL=y, and, in addition ensure that the CPU
+                to be de-jittered is marked as an adaptive-ticks CPU using
+                the "nohz_full=" boot parameter.  Bind the rcuo kthreads
+                to housekeeping CPUs, which can tolerate OS jitter.
+        b.      To the extent possible, keep the CPU out of the kernel
+                when it is non-idle, for example, by avoiding system
+                calls and by forcing both kernel threads and interrupts
+                to execute elsewhere.
+2.      Enable RCU to do its processing remotely via dyntick-idle by
+        doing all of the following:
+        a.      Build with CONFIG_NO_HZ=y and CONFIG_RCU_FAST_NO_HZ=y.
+        b.      Ensure that the CPU goes idle frequently, allowing other
+                CPUs to detect that it has passed through an RCU quiescent
+                state.  If the kernel is built with CONFIG_NO_HZ_FULL=y,
+                userspace execution also allows other CPUs to detect that
+                the CPU in question has passed through a quiescent state.
+        c.      To the extent possible, keep the CPU out of the kernel
+                when it is non-idle, for example, by avoiding system
+                calls and by forcing both kernel threads and interrupts
+                to execute elsewhere.
+
+Name: rcuc/%u
+Purpose: Execute RCU callbacks in CONFIG_RCU_BOOST=y kernels.
+To reduce its OS jitter, do at least one of the following:
+1.      Build the kernel with CONFIG_PREEMPT=n.  This prevents these
+        kthreads from being created in the first place, and also obviates
+        the need for RCU priority boosting.  This approach is feasible
+        for workloads that do not require high degrees of responsiveness.
+2.      Build the kernel with CONFIG_RCU_BOOST=n.  This prevents these
+        kthreads from being created in the first place.  This approach
+        is feasible only if your workload never requires RCU priority
+        boosting, for example, if you ensure frequent idle time on all
+        CPUs that might execute within the kernel.
+3.      Build with CONFIG_RCU_NOCB_CPU=y and CONFIG_RCU_NOCB_CPU_ALL=y,
+        which offloads all RCU callbacks to kthreads that can be moved
+        off of CPUs susceptible to OS jitter.  This approach prevents the
+        rcuc/%u kthreads from having any work to do, so that they are
+        never awakened.
+4.      Ensure that the CPU never enters the kernel, and, in particular,
+        avoid initiating any CPU hotplug operations on this CPU.  This is
+        another way of preventing any callbacks from being queued on the
+        CPU, again preventing the rcuc/%u kthreads from having any work
+        to do.
+
+Name: rcuob/%d, rcuop/%d, and rcuos/%d
+Purpose: Offload RCU callbacks from the corresponding CPU.
+To reduce its OS jitter, do at least one of the following:
+1.      Use affinity, cgroups, or other mechanism to force these kthreads
+        to execute on some other CPU.
+2.      Build with CONFIG_RCU_NOCB_CPUS=n, which will prevent these
+        kthreads from being created in the first place.  However, please
+        note that this will not eliminate OS jitter, but will instead
+        shift it to RCU_SOFTIRQ.
+
+Name: watchdog/%u
+Purpose: Detect software lockups on each CPU.
+To reduce its OS jitter, do at least one of the following:
+1.      Build with CONFIG_LOCKUP_DETECTOR=n, which will prevent these
+        kthreads from being created in the first place.
+2.      Echo a zero to /proc/sys/kernel/watchdog to disable the
+        watchdog timer.
+3.      Echo a large number of /proc/sys/kernel/watchdog_thresh in
+        order to reduce the frequency of OS jitter due to the watchdog
+        timer down to a level that is acceptable for your workload.
diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
index 504dfe4d52eb..a66c9821b5ce 100644
--- a/Documentation/power/devices.txt
+++ b/Documentation/power/devices.txt
@@ -268,7 +268,7 @@ situations.
 System Power Management Phases
 ------------------------------
 Suspending or resuming the system is done in several phases.  Different phases
-are used for standby or memory sleep states ("suspend-to-RAM") and the
+are used for freeze, standby, and memory sleep states ("suspend-to-RAM") and the
 hibernation state ("suspend-to-disk").  Each phase involves executing callbacks
 for every device before the next phase begins.  Not all busses or classes
 support all these callbacks and not all drivers use all the callbacks.  The
@@ -309,7 +309,8 @@ execute the corresponding method from dev->driver->pm instead if there is one.
 
 Entering System Suspend
 -----------------------
-When the system goes into the standby or memory sleep state, the phases are:
+When the system goes into the freeze, standby or memory sleep state,
+the phases are:
 
                 prepare, suspend, suspend_late, suspend_noirq.
 
@@ -368,7 +369,7 @@ the devices that were suspended.
 
 Leaving System Suspend
 ----------------------
-When resuming from standby or memory sleep, the phases are:
+When resuming from freeze, standby or memory sleep, the phases are:
 
                 resume_noirq, resume_early, resume, complete.
 
@@ -433,8 +434,8 @@ the system log.
 
 Entering Hibernation
 --------------------
-Hibernating the system is more complicated than putting it into the standby or
-memory sleep state, because it involves creating and saving a system image.
+Hibernating the system is more complicated than putting it into the other
+sleep states, because it involves creating and saving a system image.
 Therefore there are more phases for hibernation, with a different set of
 callbacks.  These phases always run after tasks have been frozen and memory has
 been freed.
@@ -485,8 +486,8 @@ image forms an atomic snapshot of the system state.
 
 At this point the system image is saved, and the devices then need to be
 prepared for the upcoming system shutdown.  This is much like suspending them
-before putting the system into the standby or memory sleep state, and the phases
-are similar.
+before putting the system into the freeze, standby or memory sleep state,
+and the phases are similar.
 
     9.  The prepare phase is discussed above.
 
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
index c537834af005..f1f0f59a7c47 100644
--- a/Documentation/power/interface.txt
+++ b/Documentation/power/interface.txt
@@ -7,8 +7,8 @@ running. The interface exists in /sys/power/ directory (assuming sysfs
 is mounted at /sys). 
 
 /sys/power/state controls system power state. Reading from this file
-returns what states are supported, which is hard-coded to 'standby'
-(Power-On Suspend), 'mem' (Suspend-to-RAM), and 'disk'
+returns what states are supported, which is hard-coded to 'freeze',
+'standby' (Power-On Suspend), 'mem' (Suspend-to-RAM), and 'disk'
 (Suspend-to-Disk). 
 
 Writing to this file one of those strings causes the system to
diff --git a/Documentation/power/notifiers.txt b/Documentation/power/notifiers.txt
index c2a4a346c0d9..a81fa254303d 100644
--- a/Documentation/power/notifiers.txt
+++ b/Documentation/power/notifiers.txt
@@ -15,8 +15,10 @@ A suspend/hibernation notifier may be used for this purpose.
 The subsystems or drivers having such needs can register suspend notifiers that
 will be called upon the following events by the PM core:
 
-PM_HIBERNATION_PREPARE  The system is going to hibernate or suspend, tasks will
-                        be frozen immediately.
+PM_HIBERNATION_PREPARE  The system is going to hibernate, tasks will be frozen
+                        immediately. This is different from PM_SUSPEND_PREPARE
+                        below because here we do additional work between notifiers
+                        and drivers freezing.
 
 PM_POST_HIBERNATION     The system memory state has been restored from a
                         hibernation image or an error occurred during
diff --git a/Documentation/power/states.txt b/Documentation/power/states.txt
index 4416b28630df..442d43df9b25 100644
--- a/Documentation/power/states.txt
+++ b/Documentation/power/states.txt
@@ -2,12 +2,26 @@
 System Power Management States
 
 
-The kernel supports three power management states generically, though
-each is dependent on platform support code to implement the low-level
-details for each state. This file describes each state, what they are
+The kernel supports four power management states generically, though
+one is generic and the other three are dependent on platform support
+code to implement the low-level details for each state.
+This file describes each state, what they are
 commonly called, what ACPI state they map to, and what string to write
 to /sys/power/state to enter that state
 
+state:          Freeze / Low-Power Idle
+ACPI state:     S0
+String:         "freeze"
+
+This state is a generic, pure software, light-weight, low-power state.
+It allows more energy to be saved relative to idle by freezing user
+space and putting all I/O devices into low-power states (possibly
+lower-power than available at run time), such that the processors can
+spend more time in their idle states.
+This state can be used for platforms without Standby/Suspend-to-RAM
+support, or it can be used in addition to Suspend-to-RAM (memory sleep)
+to provide reduced resume latency.
+
 
 State:          Standby / Power-On Suspend
 ACPI State:     S1
@@ -22,9 +36,6 @@ We try to put devices in a low-power state equivalent to D1, which
 also offers low power savings, but low resume latency. Not all devices
 support D1, and those that don't are left on. 
 
-A transition from Standby to the On state should take about 1-2
-seconds. 
-
 
 State:          Suspend-to-RAM
 ACPI State:     S3
@@ -42,9 +53,6 @@ transition back to the On state.
 For at least ACPI, STR requires some minimal boot-strapping code to
 resume the system from STR. This may be true on other platforms. 
 
-A transition from Suspend-to-RAM to the On state should take about
-3-5 seconds. 
-
 
 State:          Suspend-to-disk
 ACPI State:     S4
@@ -74,7 +82,3 @@ low-power state (like ACPI S4), or it may simply power down. Powering
 down offers greater savings, and allows this mechanism to work on any
 system. However, entering a real low-power state allows the user to
 trigger wake up events (e.g. pressing a key or opening a laptop lid).
-
-A transition from Suspend-to-Disk to the On state should take about 30
-seconds, though it's typically a bit more with the current
-implementation. 
diff --git a/Documentation/rapidio/rapidio.txt b/Documentation/rapidio/rapidio.txt
index c75694b35d08..a9c16c979da2 100644
--- a/Documentation/rapidio/rapidio.txt
+++ b/Documentation/rapidio/rapidio.txt
@@ -79,20 +79,63 @@ master port that is used to communicate with devices within the network.
 In order to initialize the RapidIO subsystem, a platform must initialize and
 register at least one master port within the RapidIO network. To register mport
 within the subsystem controller driver initialization code calls function
-rio_register_mport() for each available master port. After all active master
-ports are registered with a RapidIO subsystem, the rio_init_mports() routine
-is called to perform enumeration and discovery.
+rio_register_mport() for each available master port.
 
-In the current PowerPC-based implementation a subsys_initcall() is specified to
-perform controller initialization and mport registration. At the end it directly
-calls rio_init_mports() to execute RapidIO enumeration and discovery.
+RapidIO subsystem uses subsys_initcall() or device_initcall() to perform
+controller initialization (depending on controller device type).
+
+After all active master ports are registered with a RapidIO subsystem,
+an enumeration and/or discovery routine may be called automatically or
+by user-space command.
 
 4. Enumeration and Discovery
 ----------------------------
 
-When rio_init_mports() is called it scans a list of registered master ports and
-calls an enumeration or discovery routine depending on the configured role of a
-master port: host or agent.
+4.1 Overview
+------------
+
+RapidIO subsystem configuration options allow users to specify enumeration and
+discovery methods as statically linked components or loadable modules.
+An enumeration/discovery method implementation and available input parameters
+define how any given method can be attached to available RapidIO mports:
+simply to all available mports OR individually to the specified mport device.
+
+Depending on selected enumeration/discovery build configuration, there are
+several methods to initiate an enumeration and/or discovery process:
+
+  (a) Statically linked enumeration and discovery process can be started
+  automatically during kernel initialization time using corresponding module
+  parameters. This was the original method used since introduction of RapidIO
+  subsystem. Now this method relies on enumerator module parameter which is
+  'rio-scan.scan' for existing basic enumeration/discovery method.
+  When automatic start of enumeration/discovery is used a user has to ensure
+  that all discovering endpoints are started before the enumerating endpoint
+  and are waiting for enumeration to be completed.
+  Configuration option CONFIG_RAPIDIO_DISC_TIMEOUT defines time that discovering
+  endpoint waits for enumeration to be completed. If the specified timeout
+  expires the discovery process is terminated without obtaining RapidIO network
+  information. NOTE: a timed out discovery process may be restarted later using
+  a user-space command as it is described later if the given endpoint was
+  enumerated successfully.
+
+  (b) Statically linked enumeration and discovery process can be started by
+  a command from user space. This initiation method provides more flexibility
+  for a system startup compared to the option (a) above. After all participating
+  endpoints have been successfully booted, an enumeration process shall be
+  started first by issuing a user-space command, after an enumeration is
+  completed a discovery process can be started on all remaining endpoints.
+
+  (c) Modular enumeration and discovery process can be started by a command from
+  user space. After an enumeration/discovery module is loaded, a network scan
+  process can be started by issuing a user-space command.
+  Similar to the option (b) above, an enumerator has to be started first.
+
+  (d) Modular enumeration and discovery process can be started by a module
+  initialization routine. In this case an enumerating module shall be loaded
+  first.
+
+When a network scan process is started it calls an enumeration or discovery
+routine depending on the configured role of a master port: host or agent.
 
 Enumeration is performed by a master port if it is configured as a host port by
 assigning a host device ID greater than or equal to zero. A host device ID is
@@ -104,8 +147,58 @@ for it.
 The enumeration and discovery routines use RapidIO maintenance transactions
 to access the configuration space of devices.
 
-The enumeration process is implemented according to the enumeration algorithm
-outlined in the RapidIO Interconnect Specification: Annex I [1].
+4.2 Automatic Start of Enumeration and Discovery
+------------------------------------------------
+
+Automatic enumeration/discovery start method is applicable only to built-in
+enumeration/discovery RapidIO configuration selection. To enable automatic
+enumeration/discovery start by existing basic enumerator method set use boot
+command line parameter "rio-scan.scan=1".
+
+This configuration requires synchronized start of all RapidIO endpoints that
+form a network which will be enumerated/discovered. Discovering endpoints have
+to be started before an enumeration starts to ensure that all RapidIO
+controllers have been initialized and are ready to be discovered. Configuration
+parameter CONFIG_RAPIDIO_DISC_TIMEOUT defines time (in seconds) which
+a discovering endpoint will wait for enumeration to be completed.
+
+When automatic enumeration/discovery start is selected, basic method's
+initialization routine calls rio_init_mports() to perform enumeration or
+discovery for all known mport devices.
+
+Depending on RapidIO network size and configuration this automatic
+enumeration/discovery start method may be difficult to use due to the
+requirement for synchronized start of all endpoints.
+
+4.3 User-space Start of Enumeration and Discovery
+-------------------------------------------------
+
+User-space start of enumeration and discovery can be used with built-in and
+modular build configurations. For user-space controlled start RapidIO subsystem
+creates the sysfs write-only attribute file '/sys/bus/rapidio/scan'. To initiate
+an enumeration or discovery process on specific mport device, a user needs to
+write mport_ID (not RapidIO destination ID) into that file. The mport_ID is a
+sequential number (0 ... RIO_MAX_MPORTS) assigned during mport device
+registration. For example for machine with single RapidIO controller, mport_ID
+for that controller always will be 0.
+
+To initiate RapidIO enumeration/discovery on all available mports a user may
+write '-1' (or RIO_MPORT_ANY) into the scan attribute file.
+
+4.4 Basic Enumeration Method
+----------------------------
+
+This is an original enumeration/discovery method which is available since
+first release of RapidIO subsystem code. The enumeration process is
+implemented according to the enumeration algorithm outlined in the RapidIO
+Interconnect Specification: Annex I [1].
+
+This method can be configured as statically linked or loadable module.
+The method's single parameter "scan" allows to trigger the enumeration/discovery
+process from module initialization routine.
+
+This enumeration/discovery method can be started only once and does not support
+unloading if it is built as a module.
 
 The enumeration process traverses the network using a recursive depth-first
 algorithm. When a new device is found, the enumerator takes ownership of that
@@ -160,6 +253,19 @@ time period. If this wait time period expires before enumeration is completed,
 an agent skips RapidIO discovery and continues with remaining kernel
 initialization.
 
+4.5 Adding New Enumeration/Discovery Method
+-------------------------------------------
+
+RapidIO subsystem code organization allows addition of new enumeration/discovery
+methods as new configuration options without significant impact to to the core
+RapidIO code.
+
+A new enumeration/discovery method has to be attached to one or more mport
+devices before an enumeration/discovery process can be started. Normally,
+method's module initialization routine calls rio_register_scan() to attach
+an enumerator to a specified mport device (or devices). The basic enumerator
+implementation demonstrates this process.
+
 5. References
 -------------
 
diff --git a/Documentation/rapidio/sysfs.txt b/Documentation/rapidio/sysfs.txt
index 97f71ce575d6..19878179da4c 100644
--- a/Documentation/rapidio/sysfs.txt
+++ b/Documentation/rapidio/sysfs.txt
@@ -88,3 +88,20 @@ that exports additional attributes.
 
 IDT_GEN2:
  errlog - reads contents of device error log until it is empty.
+
+
+5. RapidIO Bus Attributes
+-------------------------
+
+RapidIO bus subdirectory /sys/bus/rapidio implements the following bus-specific
+attribute:
+
+  scan - allows to trigger enumeration discovery process from user space. This
+         is a write-only attribute. To initiate an enumeration or discovery
+         process on specific mport device, a user needs to write mport_ID (not
+         RapidIO destination ID) into this file. The mport_ID is a sequential
+         number (0 ... RIO_MAX_MPORTS) assigned to the mport device.
+         For example, for a machine with a single RapidIO controller, mport_ID
+         for that controller always will be 0.
+         To initiate RapidIO enumeration/discovery on all available mports
+         a user must write '-1' (or RIO_MPORT_ANY) into this attribute file.