coresight: stm: adding driver for CoreSight STM component

This driver adds support for the STM CoreSight IP block, allowing any
system compoment (HW or SW) to log and aggregate messages via a
single entity.

The CoreSight STM exposes an application defined number of channels
called stimulus port.  Configuration is done using entries in sysfs
and channels made available to userspace via configfs.

Signed-off-by: Pratik Patel <pratikp@codeaurora.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Michael Williams <michael.williams@arm.com>
Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 88 insertions, 2 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-stm b/Documentation/ABI/testing/sysfs-bus-coresight-devices-stm
new file mode 100644
index 000000000000..1dffabe7f48d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-stm
@@ -0,0 +1,53 @@
+What:		/sys/bus/coresight/devices/<memory_map>.stm/enable_source
+Date:		April 2016
+KernelVersion:	4.7
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
+Description:	(RW) Enable/disable tracing on this specific trace macrocell.
+		Enabling the trace macrocell implies it has been configured
+		properly and a sink has been identified for it.  The path
+		of coresight components linking the source to the sink is
+		configured and managed automatically by the coresight framework.
+
+What:		/sys/bus/coresight/devices/<memory_map>.stm/hwevent_enable
+Date:		April 2016
+KernelVersion:	4.7
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
+Description:	(RW) Provides access to the HW event enable register, used in
+		conjunction with HW event bank select register.
+
+What:		/sys/bus/coresight/devices/<memory_map>.stm/hwevent_select
+Date:		April 2016
+KernelVersion:	4.7
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
+Description:	(RW) Gives access to the HW event block select register
+		(STMHEBSR) in order to configure up to 256 channels.  Used in
+		conjunction with "hwevent_enable" register as described above.
+
+What:		/sys/bus/coresight/devices/<memory_map>.stm/port_enable
+Date:		April 2016
+KernelVersion:	4.7
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
+Description:	(RW) Provides access to the stimulus port enable register
+		(STMSPER).  Used in conjunction with "port_select" described
+		below.
+
+What:		/sys/bus/coresight/devices/<memory_map>.stm/port_select
+Date:		April 2016
+KernelVersion:	4.7
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
+Description:	(RW) Used to determine which bank of stimulus port bit in
+		register STMSPER (see above) apply to.
+
+What:		/sys/bus/coresight/devices/<memory_map>.stm/status
+Date:		April 2016
+KernelVersion:	4.7
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
+Description:	(R) List various control and status registers.  The specific
+		layout and content is driver specific.
+
+What:		/sys/bus/coresight/devices/<memory_map>.stm/traceid
+Date:		April 2016
+KernelVersion:	4.7
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
+Description:	(RW) Holds the trace ID that will appear in the trace stream
+		coming from this trace entity.
diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt
index 0a5c3290e732..a33c88cd5d1d 100644
--- a/Documentation/trace/coresight.txt
+++ b/Documentation/trace/coresight.txt
@@ -190,8 +190,8 @@ expected to be accessed and controlled using those entries.
 Last but not least, "struct module *owner" is expected to be set to reflect
 the information carried in "THIS_MODULE".
 
-How to use
-----------
+How to use the tracer modules
+-----------------------------
 
 Before trace collection can start, a coresight sink needs to be identify.
 There is no limit on the amount of sinks (nor sources) that can be enabled at
@@ -297,3 +297,36 @@ Info                                    Tracing enabled
 Instruction     13570831        0x8026B584      E28DD00C        false   ADD      sp,sp,#0xc
 Instruction     0       0x8026B588      E8BD8000        true    LDM      sp!,{pc}
 Timestamp                                       Timestamp: 17107041535
+
+How to use the STM module
+-------------------------
+
+Using the System Trace Macrocell module is the same as the tracers - the only
+difference is that clients are driving the trace capture rather
+than the program flow through the code.
+
+As with any other CoreSight component, specifics about the STM tracer can be
+found in sysfs with more information on each entry being found in [1]:
+
+root@genericarmv8:~# ls /sys/bus/coresight/devices/20100000.stm
+enable_source   hwevent_select  port_enable     subsystem       uevent
+hwevent_enable  mgmt            port_select     traceid
+root@genericarmv8:~#
+
+Like any other source a sink needs to be identified and the STM enabled before
+being used:
+
+root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20010000.etf/enable_sink
+root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20100000.stm/enable_source
+
+From there user space applications can request and use channels using the devfs
+interface provided for that purpose by the generic STM API:
+
+root@genericarmv8:~# ls -l /dev/20100000.stm
+crw-------    1 root     root       10,  61 Jan  3 18:11 /dev/20100000.stm
+root@genericarmv8:~#
+
+Details on how to use the generic STM API can be found here [2].
+
+[1]. Documentation/ABI/testing/sysfs-bus-coresight-devices-stm
+[2]. Documentation/trace/stm.txt