Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 132 insertions, 0 deletions

diff --git a/Documentation/driver-api/slimbus.rst b/Documentation/driver-api/slimbus.rst
new file mode 100644
index 000000000..410eec79b
--- /dev/null
+++ b/Documentation/driver-api/slimbus.rst
@@ -0,0 +1,132 @@
+============================
+Linux kernel SLIMbus support
+============================
+
+Overview
+========
+
+What is SLIMbus?
+----------------
+SLIMbus (Serial Low Power Interchip Media Bus) is a specification developed by
+MIPI (Mobile Industry Processor Interface) alliance. The bus uses master/slave
+configuration, and is a 2-wire multi-drop implementation (clock, and data).
+
+Currently, SLIMbus is used to interface between application processors of SoCs
+(System-on-Chip) and peripheral components (typically codec). SLIMbus uses
+Time-Division-Multiplexing to accommodate multiple data channels, and
+a control channel.
+
+The control channel is used for various control functions such as bus
+management, configuration and status updates. These messages can be unicast (e.g.
+reading/writing device specific values), or multicast (e.g. data channel
+reconfiguration sequence is a broadcast message announced to all devices)
+
+A data channel is used for data-transfer between 2 SLIMbus devices. Data
+channel uses dedicated ports on the device.
+
+Hardware description:
+---------------------
+SLIMbus specification has different types of device classifications based on
+their capabilities.
+A manager device is responsible for enumeration, configuration, and dynamic
+channel allocation. Every bus has 1 active manager.
+
+A generic device is a device providing application functionality (e.g. codec).
+
+Framer device is responsible for clocking the bus, and transmitting frame-sync
+and framing information on the bus.
+
+Each SLIMbus component has an interface device for monitoring physical layer.
+
+Typically each SoC contains SLIMbus component having 1 manager, 1 framer device,
+1 generic device (for data channel support), and 1 interface device.
+External peripheral SLIMbus component usually has 1 generic device (for
+functionality/data channel support), and an associated interface device.
+The generic device's registers are mapped as 'value elements' so that they can
+be written/read using SLIMbus control channel exchanging control/status type of
+information.
+In case there are multiple framer devices on the same bus, manager device is
+responsible to select the active-framer for clocking the bus.
+
+Per specification, SLIMbus uses "clock gears" to do power management based on
+current frequency and bandwidth requirements. There are 10 clock gears and each
+gear changes the SLIMbus frequency to be twice its previous gear.
+
+Each device has a 6-byte enumeration-address and the manager assigns every
+device with a 1-byte logical address after the devices report presence on the
+bus.
+
+Software description:
+---------------------
+There are 2 types of SLIMbus drivers:
+
+slim_controller represents a 'controller' for SLIMbus. This driver should
+implement duties needed by the SoC (manager device, associated
+interface device for monitoring the layers and reporting errors, default
+framer device).
+
+slim_device represents the 'generic device/component' for SLIMbus, and a
+slim_driver should implement driver for that slim_device.
+
+Device notifications to the driver:
+-----------------------------------
+Since SLIMbus devices have mechanisms for reporting their presence, the
+framework allows drivers to bind when corresponding devices report their
+presence on the bus.
+However, it is possible that the driver needs to be probed
+first so that it can enable corresponding SLIMbus device (e.g. power it up and/or
+take it out of reset). To support that behavior, the framework allows drivers
+to probe first as well  (e.g. using standard DeviceTree compatibility field).
+This creates the necessity for the driver to know when the device is functional
+(i.e. reported present). device_up callback is used for that reason when the
+device reports present and is assigned a logical address by the controller.
+
+Similarly, SLIMbus devices 'report absent' when they go down. A 'device_down'
+callback notifies the driver when the device reports absent and its logical
+address assignment is invalidated by the controller.
+
+Another notification "boot_device" is used to notify the slim_driver when
+controller resets the bus. This notification allows the driver to take necessary
+steps to boot the device so that it's functional after the bus has been reset.
+
+Driver and Controller APIs:
+---------------------------
+.. kernel-doc:: include/linux/slimbus.h
+   :internal:
+
+.. kernel-doc:: drivers/slimbus/slimbus.h
+   :internal:
+
+.. kernel-doc:: drivers/slimbus/core.c
+   :export:
+
+Clock-pause:
+------------
+SLIMbus mandates that a reconfiguration sequence (known as clock-pause) be
+broadcast to all active devices on the bus before the bus can enter low-power
+mode. Controller uses this sequence when it decides to enter low-power mode so
+that corresponding clocks and/or power-rails can be turned off to save power.
+Clock-pause is exited by waking up framer device (if controller driver initiates
+exiting low power mode), or by toggling the data line (if a slave device wants
+to initiate it).
+
+Clock-pause APIs:
+~~~~~~~~~~~~~~~~~
+.. kernel-doc:: drivers/slimbus/sched.c
+   :export:
+
+Messaging:
+----------
+The framework supports regmap and read/write apis to exchange control-information
+with a SLIMbus device. APIs can be synchronous or asynchronous.
+The header file <linux/slimbus.h> has more documentation about messaging APIs.
+
+Messaging APIs:
+~~~~~~~~~~~~~~~
+.. kernel-doc:: drivers/slimbus/messaging.c
+   :export:
+
+Streaming APIs:
+~~~~~~~~~~~~~~~
+.. kernel-doc:: drivers/slimbus/stream.c
+   :export: