[PATCH v2 6/6] Documentation: coresight: docs for config load via configfs
Mike Leach
mike.leach at linaro.org
Tue Nov 30 14:01:00 PST 2021
Add documentation covering the configfs updates that allow
binary configuration files to be loaded and unloaded via configfs,
along with the demonstration programs in samples.
Signed-off-by: Mike Leach <mike.leach at linaro.org>
---
.../trace/coresight/coresight-config.rst | 151 +++++++++++++++++-
1 file changed, 145 insertions(+), 6 deletions(-)
diff --git a/Documentation/trace/coresight/coresight-config.rst b/Documentation/trace/coresight/coresight-config.rst
index 6d5ffa6f7347..f11def230fab 100644
--- a/Documentation/trace/coresight/coresight-config.rst
+++ b/Documentation/trace/coresight/coresight-config.rst
@@ -152,7 +152,7 @@ follows::
$ cd configurations/
$ ls
- autofdo
+ autofdo last_load_status load unload
$ cd autofdo/
$ ls
description feature_refs preset1 preset3 preset5 preset7 preset9
@@ -278,9 +278,19 @@ 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 binary configuration
+file in configfs.
+
+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.
+
+An example of a custom configuration module, and generators for binary
+configuration files are found in './samples/coresight'.
-An example of a custom configuration is found in ./samples/coresight.
+
+Using a Loadable Module
+-----------------------
This creates a new configuration that uses the existing built in
strobing feature, but provides a different set of presets.
@@ -289,6 +299,135 @@ 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 select in KConfig.
+
+
+Using a Binary Configuration File
+---------------------------------
+
+Building the samples creates the 'coresight-cfg-filegen' 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-filegen.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.
+
+The program 'coresight-cfg-file-read' can read back and print a configuration
+binary. This is built using the reader from the driver code.
+
+There are additional attributes in the configurations directory - load, unload
+and last_load_status that can be used to load and unload configuration
+binary files. To load, 'cat' the binary config into the load attribute::
+
+ $ ls /config/cs-syscfg/configurations/
+ autofdo last_load_status load unload
+ $ cat example1.cscfg > /config/cs-syscfg/configurations/load
+ $ ls /config/cs-syscfg/configurations/
+ autofdo autofdo3 last_load_status load unload
+ $ cat /config/cs-syscfg/configurations/last_load_status
+ OK: configuration file loaded (autofdo3).
+
+To unload, use the same file in the unload attribute::
+
+ $ cat example1.cscfg > /config/cs-syscfg/configurations/unload
+ $ cat /config/cs-syscfg/configurations/last_load_status
+ OK: configuration file unloaded (autofdo3).
+ ls /config/cs-syscfg/configurations/
+ autofdo last_load_status load unload
+
+The generator and reader programs can also be built directly, separately from
+the kernel build by using the 'Makefile.host' file. This allows native binaries
+to be created on the host machine rather than cross compiled version for the
+target.
+
+
+Binary Configuration File Format
+--------------------------------
+
+The file format is defined in the source file **coresight-config-file.h**
+
+The source reader and generator examples produce a binary of this format.
+
+This arrangement is reproduced below:-
+
+Overall File structure
+~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ [cscfg_file_header] // Mandatory
+ [CONFIG_ELEM] // Optional - one per file, if present, first element in file.
+ [FEATURE_ELEM]* // Optional - multiple, defined by cscfg_file_header.nr_features
+
+File is invalid if both [CONFIG_ELEM] and [FEATURE_ELEM] are omitted.
+
+A file that contains only [FEATURE_ELEM] may be loaded, and the features used
+by subsequently loaded files with [CONFIG_ELEM] elements.
+
+Where [CONFIG_ELEM] is present, then **cscfg_file_header.nr_features** and
+**CONFIG_ELEM.nr_feat_refs** must have the same value.
+
+CONFIG_ELEM element
+~~~~~~~~~~~~~~~~~~~
+
+::
+
+ [cscfg_file_elem_header] // header length value to end of feature strings.
+ [cscfg_file_elem_str] // name of the configuration.
+ [cscfg_file_elem_str] // description of configuration.
+ [u16 value](nr_presets) // number of defined presets.
+ [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_file_elem_str] * (nr_feat_refs) // the features used in the configurations.
+
+FEATURE_ELEM element
+~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ [cscfg_file_elem_header] // header length is total bytes to end of param structures.
+ [cscfg_file_elem_str] // feature name.
+ [cscfg_file_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_file_elem_str] // parameter name.
+ [u64 value](param_value] // initial value.
+
+Additional definitions.
+~~~~~~~~~~~~~~~~~~~~~~~
+
+The following structures are defined in **coresight-config-file.h**
+
+ * **struct cscfg_file_header** : This structure contains an initial magic number, the total
+ length of the file, and the number of features in the file.
+ * **struct cscfg_file_elem_header**: This defines the total length and type of a CONFIG_ELEM
+ or a FEATURE_ELEM.
+ * **struct cscfg_file_elem_str**: This defines a string and its length.
+
+The magic number in cscfg_file_header is defined as two bitfields::
+
+ [31:8] Fixed magic number to identify file type.
+ [7:0] Current file format version.
+
+The following defines determine the maximum overall file size and maximum individual
+string size::
+
+ CSCFG_FILE_MAXSIZE // maximum overall file size.
+ CSCFG_FILE_STR_MAXSIZE // maximum individual string size.
--
2.17.1
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