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| author | Alexander Shishkin <alexander.shishkin@linux.intel.com> | 2016-07-14 13:39:20 +0300 |
|---|---|---|
| committer | Alexander Shishkin <alexander.shishkin@linux.intel.com> | 2016-11-18 16:54:40 +0200 |
| commit | bd566189723d919e6081b494856337ef61a23f9f (patch) | |
| tree | d3a54363dc9a1a4c27169c934096378e99af654b /Documentation/trace | |
| parent | a0ebf519b8a2666438d999c62995618c710573e5 (diff) | |
| download | lwn-bd566189723d919e6081b494856337ef61a23f9f.tar.gz lwn-bd566189723d919e6081b494856337ef61a23f9f.zip | |
stm class: Document the stm_source interface
This patch adds a description of the stm_source device class, an
interface for the kernel code to send traces over STM devices.
Cc: linux-api@vger.kernel.org
Cc: Chunyan Zhang <zhang.chunyan@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/stm.txt | 27 |
1 files changed, 24 insertions, 3 deletions
diff --git a/Documentation/trace/stm.txt b/Documentation/trace/stm.txt index ea035f9dbfd7..349869851463 100644 --- a/Documentation/trace/stm.txt +++ b/Documentation/trace/stm.txt @@ -69,12 +69,33 @@ stm device's channel mmio region is 64 bytes and hardware page size is width==64, you should be able to mmap() one page on this file descriptor and obtain direct access to an mmio region for 64 channels. +Examples of STM devices are Intel(R) Trace Hub [1] and Coresight STM +[2]. + +stm_source +========== + For kernel-based trace sources, there is "stm_source" device class. Devices of this class can be connected and disconnected to/from -stm devices at runtime via a sysfs attribute. +stm devices at runtime via a sysfs attribute called "stm_source_link" +by writing the name of the desired stm device there, for example: -Examples of STM devices are Intel(R) Trace Hub [1] and Coresight STM -[2]. +$ echo dummy_stm.0 > /sys/class/stm_source/console/stm_source_link + +For examples on how to use stm_source interface in the kernel, refer +to stm_console or stm_heartbeat drivers. + +stm_console +=========== + +One implementation of this interface also used in the example above is +the "stm_console" driver, which basically provides a one-way console +for kernel messages over an stm device. + +To configure the master/channel pair that will be assigned to this +console in the STP stream, create a "console" policy entry (see the +beginning of this text on how to do that). When initialized, it will +consume one channel. [1] https://software.intel.com/sites/default/files/managed/d3/3c/intel-th-developer-manual.pdf [2] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0444b/index.html |