intel_th: Add Global Trace Hub driver

Global Trace Hub (GTH) is the central component of Intel TH architecture;
it carries out switching between the trace sources and trace outputs, can
enable/disable tracing, perform STP encoding, internal buffering, control
backpressure from outputs to sources and so on.

This property is also reflected in the software model; GTH (switch) driver
is required for the other subdevices to probe, because it matches trace
output devices against its output ports and configures them accordingly.

It also implements an interface for output ports to request trace enabling
or disabling and a few other useful things.

For userspace, it provides an attribute group "masters", which allows
configuration of per-master trace output destinations for up to master 255
and "256+" meaning "masters 256 and above". It also provides an attribute
group to discover and configure some of the parameters of its output ports,
called "outputs". Via these the user can set up data retention policy for
an individual output port or check if it is in reset state.

Signed-off-by: Laurent Fert <laurent.fert@intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-bus-intel_th-devices-gth

@@ -0,0 +1,49 @@
+What:		/sys/bus/intel_th/devices/<intel_th_id>-gth/masters/*
+Date:		June 2015
+KernelVersion:	4.3
+Contact:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
+Description:	(RW) Configure output ports for STP masters. Writing -1
+		disables a master; any
+
+What:		/sys/bus/intel_th/devices/<intel_th_id>-gth/outputs/[0-7]_port
+Date:		June 2015
+KernelVersion:	4.3
+Contact:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
+Description:	(RO) Output port type:
+		  0: not present,
+		  1: MSU (Memory Storage Unit)
+		  2: CTP (Common Trace Port)
+		  4: PTI (MIPI PTI).
+
+What:		/sys/bus/intel_th/devices/<intel_th_id>-gth/outputs/[0-7]_drop
+Date:		June 2015
+KernelVersion:	4.3
+Contact:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
+Description:	(RW) Data retention policy setting: keep (0) or drop (1)
+		incoming data while output port is in reset.
+
+What:		/sys/bus/intel_th/devices/<intel_th_id>-gth/outputs/[0-7]_null
+Date:		June 2015
+KernelVersion:	4.3
+Contact:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
+Description:	(RW) STP NULL packet generation: enabled (1) or disabled (0).
+
+What:		/sys/bus/intel_th/devices/<intel_th_id>-gth/outputs/[0-7]_flush
+Date:		June 2015
+KernelVersion:	4.3
+Contact:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
+Description:	(RW) Force flush data from byte packing buffer for the output
+		port.
+
+What:		/sys/bus/intel_th/devices/<intel_th_id>-gth/outputs/[0-7]_reset
+Date:		June 2015
+KernelVersion:	4.3
+Contact:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
+Description:	(RO) Output port is in reset (1).
+
+What:		/sys/bus/intel_th/devices/<intel_th_id>-gth/outputs/[0-7]_smcfreq
+Date:		June 2015
+KernelVersion:	4.3
+Contact:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
+Description:	(RW) STP sync packet frequency for the port. Specifies the
+		number of clocks between mainenance packets.

drivers/hwtracing/intel_th/Kconfig

@@ -24,6 +24,16 @@ config INTEL_TH_PCI
 
 	  Say Y here to enable PCI Intel TH support.
 
+config INTEL_TH_GTH
+	tristate "Intel(R) Trace Hub Global Trace Hub"
+	help
+	  Global Trace Hub (GTH) is the central component of the
+	  Intel TH infrastructure and acts as a switch for source
+	  and output devices. This driver is required for other
+	  Intel TH subdevices to initialize.
+
+	  Say Y here to enable GTH subdevice of Intel(R) Trace Hub.
+
 config INTEL_TH_DEBUG
 	bool "Intel(R) Trace Hub debugging"
 	depends on DEBUG_FS

drivers/hwtracing/intel_th/Makefile

@@ -4,3 +4,6 @@ intel_th-$(CONFIG_INTEL_TH_DEBUG) += debug.o
 
 obj-$(CONFIG_INTEL_TH_PCI)	+= intel_th_pci.o
 intel_th_pci-y			:= pci.o
+
+obj-$(CONFIG_INTEL_TH_GTH)	+= intel_th_gth.o
+intel_th_gth-y			:= gth.o