[PATCH v2 6/6] Documentation: coresight: docs for config load via configfs

[Mike Leach <mike.leach@linaro.org>]

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@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


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel