HI Mathieu,
On Fri, 26 Nov 2021 at 18:26, Mathieu Poirier mathieu.poirier@linaro.org wrote:
On Wed, Nov 24, 2021 at 08:00:38PM +0000, Mike Leach wrote:
Update the CoreSight System Configuration document to cover the use of loadable modules to add configurations and features to the system.
Signed-off-by: Mike Leach mike.leach@linaro.org
.../trace/coresight/coresight-config.rst | 62 ++++++++++++++++++- 1 file changed, 59 insertions(+), 3 deletions(-)
diff --git a/Documentation/trace/coresight/coresight-config.rst b/Documentation/trace/coresight/coresight-config.rst index 6ed13398ca2c..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::
@@ -236,3 +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.
Shouldn't all instances in the above section be configfs rather than sysfs? If so should I make the changes?
What I am trying to explain there is that when using sysfs to control CoreSight, it is possible to set a configuration using configfs, which is then used when a tracer is enabled under sysfs.
Mike
I have your patchset on stanby in my local coresight-next tree - just let me know.
Thanks, Mathieu
+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.
2.17.1