Add documentation covering the updates that allow configuration tables to be loaded and unloaded via configfs, along with the demonstration programs in tools/coresight.
Cc: Jonathan Corbet corbet@lwn.net Cc: linux-doc@vger.kernel.org Signed-off-by: Mike Leach mike.leach@linaro.org --- .../trace/coresight/coresight-config.rst | 287 ++++++++++++++++-- 1 file changed, 264 insertions(+), 23 deletions(-)
diff --git a/Documentation/trace/coresight/coresight-config.rst b/Documentation/trace/coresight/coresight-config.rst index 6d5ffa6f7347..235cc6443a86 100644 --- a/Documentation/trace/coresight/coresight-config.rst +++ b/Documentation/trace/coresight/coresight-config.rst @@ -109,20 +109,20 @@ Operation
The following steps take place in the operation of a configuration.
-1) In this example, the configuration is 'autofdo', which has an - associated feature 'strobing' that works on ETMv4 CoreSight Devices. +1) In this example, the configuration is ``autofdo``, which has an + associated feature ``strobing`` that works on ETMv4 CoreSight Devices.
-2) The configuration is enabled. For example 'perf' may select the +2) The configuration is enabled. For example ``perf`` may select the configuration as part of its command line::
perf record -e cs_etm/autofdo/ myapp
- which will enable the 'autofdo' configuration. + which will enable the ``autofdo`` configuration.
3) perf starts tracing on the system. As each ETMv4 that perf uses for trace is enabled, the configuration manager will check if the ETMv4 has a feature that relates to the currently active configuration. - In this case 'strobing' is enabled & programmed into the ETMv4. + In this case ``strobing`` is enabled & programmed into the ETMv4.
4) When the ETMv4 is disabled, any registers marked as needing to be saved will be read back. @@ -136,18 +136,18 @@ Viewing Configurations and Features The set of configurations and features that are currently loaded into the system can be viewed using the configfs API.
-Mount configfs as normal and the 'cs-syscfg' subsystem will appear:: +Mount configfs as normal and the ``cs-syscfg`` subsystem will appear::
$ ls /config cs-syscfg stp-policy
-This has two sub-directories:: +This has two sub-directories, with the load and unload attribute files::
$ cd cs-syscfg/ $ ls - configurations features + configurations features load unload
-The system has the configuration 'autofdo' built in. It may be examined as +The system has the configuration ``autofdo`` built in. It may be examined as follows::
$ cd configurations/ @@ -162,7 +162,7 @@ follows:: $ 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 @@ -170,7 +170,7 @@ 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 +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 @@ -210,18 +210,18 @@ Using Configurations in perf ============================
The configurations loaded into the CoreSight configuration management are -also declared in the perf 'cs_etm' event infrastructure so that they can +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 cpu0 cpu2 events nr_addr_filters power subsystem uevent cpu1 cpu3 format perf_event_mux_interval_ms sinks type
-The key directory here is 'events' - a generic perf directory which allows +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.
-The entry in the 'events' directory uses perfs built in syntax generator +The entry in the ``events`` directory uses perfs built in syntax generator to substitute the syntax for the name when evaluating the command::
$ ls events/ @@ -229,7 +229,7 @@ to substitute the syntax for the name when evaluating the command:: $ cat events/autofdo configid=0xa7c3dddd
-The 'autofdo' configuration may be selected on the perf command line:: +The ``autofdo`` configuration may be selected on the perf command line::
$ perf record -e cs_etm/autofdo/u --per-thread <application>
@@ -246,7 +246,7 @@ 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. +In a configuration there are ``enable`` and ``preset`` files.
To enable a configuration for use with sysfs::
@@ -256,13 +256,13 @@ To enable a configuration for use with sysfs:: 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:: +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. +<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. @@ -278,9 +278,28 @@ Creating and Loading Custom Configurations ==========================================
Custom configurations and / or features can be dynamically loaded into the -system by using a loadable module. +system by using a loadable module, or by loading a configuration table +through in configfs.
-An example of a custom configuration is found in ./samples/coresight. +Loaded 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. + + +Using a Loadable Module +----------------------- + +A new configuration or set of features can be created using the internal +structures used in the drivers, by writing a loadable module that defines +the configuration, and loading this into the kernel at runtime. + +Creating a custom configuration in this way requires the user to compile the +module for the specific kernel in use, which limits portability. + +Module Example +~~~~~~~~~~~~~~ + +An example of a custom configuration module 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. @@ -289,6 +308,228 @@ 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. +The file ``coresight-cfg-sample.c`` contains the configuration and module +initialisation code needed to create the loadable module. + +This will be built alongside the kernel modules if selected in KConfig. +(select ``CONFIG_SAMPLE_CORESIGHT_SYSCFG``). + + +Using a Configuration Table File +-------------------------------- + +Configurations and features can also be dynamically loaded at runtime +using a compact binary table format described below. + +Upon load, this table is validated, expanded into the internal structures +needed for load into the CoreSight subsystem, and loaded into the relevant +CoreSight devices. + +There are additional attributes in the cs-syscfg directory - ``load_table`` +and ``unload_last_table`` that can be used to load and unload configuration +tables. + +As described above, in order to respect configuration dependencies, unload +order is scrictly enforced to be the reverse of load order. + +Load and unload cannot be done if trace is in progress using a configuration. + +To load, 'cat' the table file into the load attribute:: + + $ ls /config/cs-syscfg + configurations features load_table show_last_load unload_last_table + $ cat example1.cscfg > /config/cs-syscfg/load_table + $ ls /config/cs-syscfg/configurations/ + autofdo autofdo3 + +``unload_last_table`` can be used to unload the last loaded configuration, +but only if this was loaded as a configuration table. + +To unload, write a non-zero value to ``unload_last_table``. This will unload +the last loaded table - unless another configuration or feature has been +loaded as a loadable module after the last table load:: + + $ echo 1 > /config/cs-syscfg/unload_last_table + ls /config/cs-syscfg/configurations/ + autofdo + +The type of the last loaded configuration can be determined by reading the +``show_last_load`` attribute:: + + $ cat /config/cs-syscfg/show_last_load + load name: autofdo3 + load type: Runtime Dynamic table load + (configurations: autofdo3 ) + (features: None ) + +This shows the key elements of the loaded configuration - the type of load, +load name, and any configurations and features loaded by the table. + +Unload will fail if the last loaded item was not a dynamic loaded table. +When using ``show_last_load`` a non table load will show:: + + cat /config/cs-syscfg/show_last_load + load name: [Not Set] + load type: Loadable module + + +Generation tools and table examples +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ``./tools/coresight`` directory contains example programs to generate and +read and print binary configuration table files. + +Building the tools creates the ``coresight-cfg-file-gen`` program that will +generate a configuration binary ``example1.cscfg`` that can be loaded into the +system using configfs. The configuration declared in the source file +``coresight-cfg-example1.c`` is named ``autofdo3`` - the name that will be used +once loaded. + +The source files ``coresight-cfg-bufw.h`` and ``coresight-cfg-bufw.c`` provide a +standard function to convert a configuration declared in 'C' into the correct +binary buffer format. These files can be re-used to create new custom +configurations. Alternatively, additional examples can be added to the +``coresight-cfg-file-gen`` program:: + + $ ./coresight-cfg-file-gen + Coresight Configuration file Generator + + Generating example1 example + Generating example2 example + +The program ``coresight-cfg-file-read`` can read back and print a configuration +binary. This is built using the file reader from the driver code +(``coresight-config-file.c``), which is copied over into ``./tools/coresight`` at +build time.:: + + ./coresight-cfg-file-read example1.cscfg + CoreSight Configuration file reader + ============================================ + + Configuration 1 + Name:- autofdo3 + Description:- + Setup ETMs with strobing for autofdo + Supplied presets allow experimentation with mark-space ratio for various loads + + Uses 1 features:- + Feature-1: strobing + + Provides 4 sets of preset values, 2 presets per set + set[0]: 0x7d0, 0x64, + set[1]: 0x7d0, 0x3e8, + set[2]: 0x7d0, 0x1388, + set[3]: 0x7d0, 0x2710, + + ============================================ + File contains no features + + +CoreSight Configuration Table Format +------------------------------------ + +The file format is defined in the source file ``coresight-config-table.h`` + +The source reader and generator examples use/produce a table in this format, +as a binary file. + +This arrangement is reproduced below:- + +Overall Table structure +~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + [cscfg_table_header] // Mandatory + [CONFIG_ELEM]* // Optional - multiple, defined by cscfg_table_header.nr_configs + [FEATURE_ELEM]* // Optional - multiple, defined by cscfg_table_header.nr_features + +Table is invalid if both [CONFIG_ELEM] and [FEATURE_ELEM] are omitted. + +A table that contains only [FEATURE_ELEM] may be loaded, and the features used +by subsequently loaded files with [CONFIG_ELEM] elements. + +Element Name Strings +~~~~~~~~~~~~~~~~~~~~ + +Configuration name strings are required to consist of alphanumeric characters and '_' only. Other special characters are not permitted. + +For example ``my_config_2`` is a valid name, while ``this-bad-config#5`` will not work. + +This is in order to comply with the requirements of the perf command line. + +It is recommended that Feature and Parameter names use the same convention to allow for future enhancements to the command line syntax. + +CONFIG_ELEM element +~~~~~~~~~~~~~~~~~~~ + +:: + + [cscfg_table_elem_header] // header length value to end of feature strings. + [cscfg_table_elem_str] // name of the configuration. + // (see element string name requirements) + [cscfg_table_elem_str] // description of configuration. + [u16 value](nr_presets) // number of defined sets presets values. + [u32 value](nr_total_params) // total parameters defined by all used features. + [u16 value](nr_feat_refs) // number of features referenced by the configuration + [u64 values] * (nr_presets * nr_total_params) // the preset values. + [cscfg_table_elem_str] * (nr_feat_refs) // names of features used in the configurations. + +FEATURE_ELEM element +~~~~~~~~~~~~~~~~~~~~ + +:: + + [cscfg_table_elem_header] // header length is total bytes to end of param structures. + [cscfg_table_elem_str] // feature name. + [cscfg_table_elem_str] // feature description. + [u32 value](match_flags) // flags to associate the feature with a device. + [u16 value](nr_regs) // number of registers. + [u16 value](nr_params) // number of parameters. + [cscfg_regval_desc struct] * (nr_regs) // register definitions + [PARAM_ELEM] * (nr_params) // parameters definitions + +PARAM_ELEM element +~~~~~~~~~~~~~~~~~~ + +:: + + [cscfg_table_elem_str] // parameter name. + [u64 value](param_value) // initial value. + +Additional definitions +~~~~~~~~~~~~~~~~~~~~~~ + +The following structures are defined in ``coresight-config-file.h`` + + * ``struct cscfg_table_header`` : This structure contains an initial magic number, the total + length of the table, and the number of configurations and features in the table. + * ``struct cscfg_table_elem_header``: This defines the total length and type of a CONFIG_ELEM + or a FEATURE_ELEM. + * ``struct cscfg_table_elem_str``: This defines a string and its length. + +The magic number in cscfg_table_header is defined as two bitfields:: + + [31:8] Fixed magic number to identify table type. + [7:0] Current table format version. + +The following defines determine the maximum overall table size and maximum individual +string size + + * ``CSCFG_TABLE_MAXSIZE`` : maximum overall table size. + * ``CSCFG_TABLE_STR_MAXSIZE`` : maximum individual string size. + +Load Dependencies +~~~~~~~~~~~~~~~~~ + +Files may be unloaded only in the strict reverse order of loading. This is enforced by the +configuration system. + +This is to ensure that any load dependencies are maintained. + +A configuration table that contains a CONFIG_ELEM that references named features "feat_A" and "feat_B" will load only if either:- + +a) "feat_A" and/or "feat_B" has been loaded previously, or are present as built-in / module loaded features. +b) "feat_A" and/or "feat_B" are declared as FEAT_ELEM in the same table as the CONFIG_ELEM. + +Tables that contain features or configurations with the same names as those already loaded will fail to load.