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authorGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-12-21 10:07:07 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-12-21 10:07:07 +0100
commitfdcee305c08a27c8d5d2d03eb5b2656ac3e4a0cc (patch)
tree69e990b2538a4104e1f6b5e1358532bb68e210b5 /Documentation/trace
parenta4c1aaf97bf1d7102ac538beaf7846b7c5d8c97d (diff)
parentefa56eddf5d5c03a90abe708431f16c12c291837 (diff)
Merge tag 'coresight-next-v5.17' of gitolite.kernel.org:pub/scm/linux/kernel/git/coresight/linux into char-misc-next
Mathieu writes: Coresight changes for v5.17 This pull request includes: - A patch that uses devm_bitmap_zalloc() instead of the open-coded equivalent. - Work to make coresight complex configuration loadable via modules. - Some coresight documentation updates. Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> * tag 'coresight-next-v5.17' of gitolite.kernel.org:pub/scm/linux/kernel/git/coresight/linux: coresight: core: Fix typo in a comment Documentation: coresight: Update coresight configuration docs coresight: configfs: Allow configfs to activate configuration coresight: syscfg: Example CoreSight configuration loadable module coresight: syscfg: Update load API for config loadable modules coresight: configuration: Update API to permit dynamic load/unload coresight: configuration: Update API to introduce load owner concept Documentation: coresight: Fix documentation issue coresight: Use devm_bitmap_zalloc when applicable
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/coresight/coresight-config.rst78
1 files changed, 64 insertions, 14 deletions
diff --git a/Documentation/trace/coresight/coresight-config.rst b/Documentation/trace/coresight/coresight-config.rst
index a4e3ef295240..6d5ffa6f7347 100644
--- a/Documentation/trace/coresight/coresight-config.rst
+++ b/Documentation/trace/coresight/coresight-config.rst
@@ -155,14 +155,14 @@ follows::
autofdo
$ cd autofdo/
$ ls
- description preset1 preset3 preset5 preset7 preset9
- feature_refs preset2 preset4 preset6 preset8
+ description feature_refs preset1 preset3 preset5 preset7 preset9
+ enable preset preset2 preset4 preset6 preset8
$ cat description
Setup ETMs with strobing for autofdo
$ cat feature_refs
strobing
-Each preset declared has a preset<n> subdirectory declared. The values for
+Each preset declared has a 'preset<n>' subdirectory declared. The values for
the preset can be examined::
$ cat preset1/values
@@ -170,6 +170,9 @@ the preset can be examined::
$ cat preset2/values
strobing.window = 0x1388 strobing.period = 0x4
+The 'enable' and 'preset' files allow the control of a configuration when
+using CoreSight with sysfs.
+
The features referenced by the configuration can be examined in the features
directory::
@@ -211,19 +214,13 @@ also declared in the perf 'cs_etm' event infrastructure so that they can
be selected when running trace under perf::
$ ls /sys/devices/cs_etm
- configurations format perf_event_mux_interval_ms sinks type
- events nr_addr_filters power
-
-Key directories here are 'configurations' - which lists the loaded
-configurations, and 'events' - a generic perf directory which allows
-selection on the perf command line.::
+ cpu0 cpu2 events nr_addr_filters power subsystem uevent
+ cpu1 cpu3 format perf_event_mux_interval_ms sinks type
- $ ls configurations/
- autofdo
- $ cat configurations/autofdo
- 0xa7c3dddd
+The key directory here is 'events' - a generic perf directory which allows
+selection on the perf command line. As with the sinks entries, this provides
+a hash of the configuration name.
-As with the sinks entries, this provides a hash of the configuration name.
The entry in the 'events' directory uses perfs built in syntax generator
to substitute the syntax for the name when evaluating the command::
@@ -242,3 +239,56 @@ A preset to override the current parameter values can also be selected::
When configurations are selected in this way, then the trace sink used is
automatically selected.
+
+Using Configurations in sysfs
+=============================
+
+Coresight can be controlled using sysfs. When this is in use then a configuration
+can be made active for the devices that are used in the sysfs session.
+
+In a configuration there are 'enable' and 'preset' files.
+
+To enable a configuration for use with sysfs::
+
+ $ cd configurations/autofdo
+ $ echo 1 > enable
+
+This will then use any default parameter values in the features - which can be
+adjusted as described above.
+
+To use a preset<n> set of parameter values::
+
+ $ echo 3 > preset
+
+This will select preset3 for the configuration.
+The valid values for preset are 0 - to deselect presets, and any value of
+<n> where a preset<n> sub-directory is present.
+
+Note that the active sysfs configuration is a global parameter, therefore
+only a single configuration can be active for sysfs at any one time.
+Attempting to enable a second configuration will result in an error.
+Additionally, attempting to disable the configuration while in use will
+also result in an error.
+
+The use of the active configuration by sysfs is independent of the configuration
+used in perf.
+
+
+Creating and Loading Custom Configurations
+==========================================
+
+Custom configurations and / or features can be dynamically loaded into the
+system by using a loadable module.
+
+An example of a custom configuration is found in ./samples/coresight.
+
+This creates a new configuration that uses the existing built in
+strobing feature, but provides a different set of presets.
+
+When the module is loaded, then the configuration appears in the configfs
+file system and is selectable in the same way as the built in configuration
+described above.
+
+Configurations can use previously loaded features. The system will ensure
+that it is not possible to unload a feature that is currently in use, by
+enforcing the unload order as the strict reverse of the load order.