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 <[e-mail]>

* 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

Documentation/trace/coresight/coresight-config.rst

···
     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
     strobing.window = 0x1388 strobing.period = 0x2
     $ 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::
···
 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
+    cpu0  cpu2  events  nr_addr_filters		power  subsystem  uevent
+    cpu1  cpu3  format  perf_event_mux_interval_ms	sinks  type
 
-Key directories here are 'configurations' - which lists the loaded
-configurations, and 'events' - a generic perf directory which allows
-selection on the perf command line.::
+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.
 
-    $ ls configurations/
-    autofdo
-    $ cat configurations/autofdo
-    0xa7c3dddd
-
-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::
 
···
 
 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.

MAINTAINERS

···
 F:	drivers/hwtracing/coresight/*
 F:	include/dt-bindings/arm/coresight-cti-dt.h
 F:	include/linux/coresight*
+F:	samples/coresight/*
 F:	tools/perf/arch/arm/util/auxtrace.c
 F:	tools/perf/arch/arm/util/cs-etm.c
 F:	tools/perf/arch/arm/util/cs-etm.h

drivers/hwtracing/coresight/coresight-cfg-preload.c

···
 	NULL
 };
 
+static struct cscfg_load_owner_info preload_owner = {
+	.type = CSCFG_OWNER_PRELOAD,
+};
+
 /* preload called on initialisation */
-int cscfg_preload(void)
+int cscfg_preload(void *owner_handle)
 {
-	return cscfg_load_config_sets(preload_cfgs, preload_feats);
+	preload_owner.owner_handle = owner_handle;
+	return cscfg_load_config_sets(preload_cfgs, preload_feats, &preload_owner);
 }

drivers/hwtracing/coresight/coresight-config.h

···
  * @params_desc: array of parameters used.
  * @nr_regs:	 number of registers used.
  * @regs_desc:	 array of registers used.
+ * @load_owner:	 handle to load owner for dynamic load and unload of features.
+ * @fs_group:	 reference to configfs group for dynamic unload.
  */
 struct cscfg_feature_desc {
 	const char *name;
···
 	struct cscfg_parameter_desc *params_desc;
 	int nr_regs;
 	struct cscfg_regval_desc *regs_desc;
+	void *load_owner;
+	struct config_group *fs_group;
 };
 
 /**
···
  * @presets:		Array of preset values.
  * @event_ea:		Extended attribute for perf event value
  * @active_cnt:		ref count for activate on this configuration.
- *
+ * @load_owner:		handle to load owner for dynamic load and unload of configs.
+ * @fs_group:		reference to configfs group for dynamic unload.
  */
 struct cscfg_config_desc {
 	const char *name;
···
 	const u64 *presets; /* nr_presets * nr_total_params */
 	struct dev_ext_attribute *event_ea;
 	atomic_t active_cnt;
+	void *load_owner;
+	struct config_group *fs_group;
 };
 
 /**

drivers/hwtracing/coresight/coresight-core.c

···
  * coresight_grab_device - Power up this device and any of the helper
  * devices connected to it for trace operation. Since the helper devices
  * don't appear on the trace path, they should be handled along with the
- * the master device.
+ * master device.
  */
 static int coresight_grab_device(struct coresight_device *csdev)
 {

drivers/hwtracing/coresight/coresight-etm4x-core.c

···
 {
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct etm4_enable_arg arg = { };
-	int ret;
+	unsigned long cfg_hash;
+	int ret, preset;
+
+	/* enable any config activated by configfs */
+	cscfg_config_sysfs_get_active_cfg(&cfg_hash, &preset);
+	if (cfg_hash) {
+		ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset);
+		if (ret)
+			return ret;
+	}
 
 	spin_lock(&drvdata->spinlock);
 

drivers/hwtracing/coresight/coresight-stm.c

···
 {
 	int ret;
 	void __iomem *base;
-	unsigned long *guaranteed;
 	struct device *dev = &adev->dev;
 	struct coresight_platform_data *pdata = NULL;
 	struct stm_drvdata *drvdata;
 	struct resource *res = &adev->res;
 	struct resource ch_res;
-	size_t bitmap_size;
 	struct coresight_desc desc = { 0 };
 
 	desc.name = coresight_alloc_device_name(&stm_devs, dev);
···
 	else
 		drvdata->numsp = stm_num_stimulus_port(drvdata);
 
-	bitmap_size = BITS_TO_LONGS(drvdata->numsp) * sizeof(long);
-
-	guaranteed = devm_kzalloc(dev, bitmap_size, GFP_KERNEL);
-	if (!guaranteed)
+	drvdata->chs.guaranteed = devm_bitmap_zalloc(dev, drvdata->numsp,
+						     GFP_KERNEL);
+	if (!drvdata->chs.guaranteed)
 		return -ENOMEM;
-	drvdata->chs.guaranteed = guaranteed;
 
 	spin_lock_init(&drvdata->spinlock);
 

drivers/hwtracing/coresight/coresight-syscfg-configfs.c

···
 
 #include <linux/configfs.h>
 
+#include "coresight-config.h"
 #include "coresight-syscfg-configfs.h"
 
 /* create a default ci_type. */
···
 }
 CONFIGFS_ATTR_RO(cscfg_cfg_, values);
 
+static ssize_t cscfg_cfg_enable_show(struct config_item *item, char *page)
+{
+	struct cscfg_fs_config *fs_config = container_of(to_config_group(item),
+							 struct cscfg_fs_config, group);
+
+	return scnprintf(page, PAGE_SIZE, "%d\n", fs_config->active);
+}
+
+static ssize_t cscfg_cfg_enable_store(struct config_item *item,
+					const char *page, size_t count)
+{
+	struct cscfg_fs_config *fs_config = container_of(to_config_group(item),
+							 struct cscfg_fs_config, group);
+	int err;
+	bool val;
+
+	err = kstrtobool(page, &val);
+	if (!err)
+		err = cscfg_config_sysfs_activate(fs_config->config_desc, val);
+	if (!err) {
+		fs_config->active = val;
+		if (val)
+			cscfg_config_sysfs_set_preset(fs_config->preset);
+	}
+	return err ? err : count;
+}
+CONFIGFS_ATTR(cscfg_cfg_, enable);
+
+static ssize_t cscfg_cfg_preset_show(struct config_item *item, char *page)
+{
+	struct cscfg_fs_config *fs_config = container_of(to_config_group(item),
+							 struct cscfg_fs_config, group);
+
+	return scnprintf(page, PAGE_SIZE, "%d\n", fs_config->preset);
+}
+
+static ssize_t cscfg_cfg_preset_store(struct config_item *item,
+					     const char *page, size_t count)
+{
+	struct cscfg_fs_config *fs_config = container_of(to_config_group(item),
+							 struct cscfg_fs_config, group);
+	int preset, err;
+
+	err = kstrtoint(page, 0, &preset);
+	if (!err) {
+		/*
+		 * presets start at 1, and go up to max (15),
+		 * but the config may provide fewer.
+		 */
+		if ((preset < 1) || (preset > fs_config->config_desc->nr_presets))
+			err = -EINVAL;
+	}
+
+	if (!err) {
+		/* set new value */
+		fs_config->preset = preset;
+		/* set on system if active */
+		if (fs_config->active)
+			cscfg_config_sysfs_set_preset(fs_config->preset);
+	}
+	return err ? err : count;
+}
+CONFIGFS_ATTR(cscfg_cfg_, preset);
+
 static struct configfs_attribute *cscfg_config_view_attrs[] = {
 	&cscfg_cfg_attr_description,
 	&cscfg_cfg_attr_feature_refs,
+	&cscfg_cfg_attr_enable,
+	&cscfg_cfg_attr_preset,
 	NULL,
 };
 
···
 	if (IS_ERR(new_group))
 		return PTR_ERR(new_group);
 	err =  configfs_register_group(&cscfg_configs_grp, new_group);
+	if (!err)
+		config_desc->fs_group = new_group;
 	return err;
+}
+
+void cscfg_configfs_del_config(struct cscfg_config_desc *config_desc)
+{
+	if (config_desc->fs_group) {
+		configfs_unregister_group(config_desc->fs_group);
+		config_desc->fs_group = NULL;
+	}
 }
 
 static struct config_item_type cscfg_features_type = {
···
 	if (IS_ERR(new_group))
 		return PTR_ERR(new_group);
 	err =  configfs_register_group(&cscfg_features_grp, new_group);
+	if (!err)
+		feat_desc->fs_group = new_group;
 	return err;
+}
+
+void cscfg_configfs_del_feature(struct cscfg_feature_desc *feat_desc)
+{
+	if (feat_desc->fs_group) {
+		configfs_unregister_group(feat_desc->fs_group);
+		feat_desc->fs_group = NULL;
+	}
 }
 
 int cscfg_configfs_init(struct cscfg_manager *cscfg_mgr)

drivers/hwtracing/coresight/coresight-syscfg-configfs.h

···
 struct cscfg_fs_config {
 	struct cscfg_config_desc *config_desc;
 	struct config_group group;
+	bool active;
+	int preset;
 };
 
 /* container for feature view */
···
 void cscfg_configfs_release(struct cscfg_manager *cscfg_mgr);
 int cscfg_configfs_add_config(struct cscfg_config_desc *config_desc);
 int cscfg_configfs_add_feature(struct cscfg_feature_desc *feat_desc);
+void cscfg_configfs_del_config(struct cscfg_config_desc *config_desc);
+void cscfg_configfs_del_feature(struct cscfg_feature_desc *feat_desc);
 
 #endif /* CORESIGHT_SYSCFG_CONFIGFS_H */

drivers/hwtracing/coresight/coresight-syscfg.c

···
 static int cscfg_load_feat(struct cscfg_feature_desc *feat_desc)
 {
 	int err;
+	struct cscfg_feature_desc *feat_desc_exist;
+
+	/* new feature must have unique name */
+	list_for_each_entry(feat_desc_exist, &cscfg_mgr->feat_desc_list, item) {
+		if (!strcmp(feat_desc_exist->name, feat_desc->name))
+			return -EEXIST;
+	}
 
 	/* add feature to any matching registered devices */
 	err = cscfg_add_feat_to_csdevs(feat_desc);
···
 static int cscfg_load_config(struct cscfg_config_desc *config_desc)
 {
 	int err;
+	struct cscfg_config_desc *config_desc_exist;
+
+	/* new configuration must have a unique name */
+	list_for_each_entry(config_desc_exist, &cscfg_mgr->config_desc_list, item) {
+		if (!strcmp(config_desc_exist->name, config_desc->name))
+			return -EEXIST;
+	}
 
 	/* validate features are present */
 	err = cscfg_check_feat_for_cfg(config_desc);
···
 	return err;
 }
 
+/*
+ * Conditionally up reference count on owner to prevent unload.
+ *
+ * module loaded configs need to be locked in to prevent premature unload.
+ */
+static int cscfg_owner_get(struct cscfg_load_owner_info *owner_info)
+{
+	if ((owner_info->type == CSCFG_OWNER_MODULE) &&
+	    (!try_module_get(owner_info->owner_handle)))
+		return -EINVAL;
+	return 0;
+}
+
+/* conditionally lower ref count on an owner */
+static void cscfg_owner_put(struct cscfg_load_owner_info *owner_info)
+{
+	if (owner_info->type == CSCFG_OWNER_MODULE)
+		module_put(owner_info->owner_handle);
+}
+
+static void cscfg_remove_owned_csdev_configs(struct coresight_device *csdev, void *load_owner)
+{
+	struct cscfg_config_csdev *config_csdev, *tmp;
+
+	if (list_empty(&csdev->config_csdev_list))
+		return;
+
+	list_for_each_entry_safe(config_csdev, tmp, &csdev->config_csdev_list, node) {
+		if (config_csdev->config_desc->load_owner == load_owner)
+			list_del(&config_csdev->node);
+	}
+}
+
+static void cscfg_remove_owned_csdev_features(struct coresight_device *csdev, void *load_owner)
+{
+	struct cscfg_feature_csdev *feat_csdev, *tmp;
+
+	if (list_empty(&csdev->feature_csdev_list))
+		return;
+
+	list_for_each_entry_safe(feat_csdev, tmp, &csdev->feature_csdev_list, node) {
+		if (feat_csdev->feat_desc->load_owner == load_owner)
+			list_del(&feat_csdev->node);
+	}
+}
+
+/*
+ * removal is relatively easy - just remove from all lists, anything that
+ * matches the owner. Memory for the descriptors will be managed by the owner,
+ * memory for the csdev items is devm_ allocated with the individual csdev
+ * devices.
+ */
+static void cscfg_unload_owned_cfgs_feats(void *load_owner)
+{
+	struct cscfg_config_desc *config_desc, *cfg_tmp;
+	struct cscfg_feature_desc *feat_desc, *feat_tmp;
+	struct cscfg_registered_csdev *csdev_item;
+
+	/* remove from each csdev instance feature and config lists */
+	list_for_each_entry(csdev_item, &cscfg_mgr->csdev_desc_list, item) {
+		/*
+		 * for each csdev, check the loaded lists and remove if
+		 * referenced descriptor is owned
+		 */
+		cscfg_remove_owned_csdev_configs(csdev_item->csdev, load_owner);
+		cscfg_remove_owned_csdev_features(csdev_item->csdev, load_owner);
+	}
+
+	/* remove from the config descriptor lists */
+	list_for_each_entry_safe(config_desc, cfg_tmp, &cscfg_mgr->config_desc_list, item) {
+		if (config_desc->load_owner == load_owner) {
+			cscfg_configfs_del_config(config_desc);
+			etm_perf_del_symlink_cscfg(config_desc);
+			list_del(&config_desc->item);
+		}
+	}
+
+	/* remove from the feature descriptor lists */
+	list_for_each_entry_safe(feat_desc, feat_tmp, &cscfg_mgr->feat_desc_list, item) {
+		if (feat_desc->load_owner == load_owner) {
+			cscfg_configfs_del_feature(feat_desc);
+			list_del(&feat_desc->item);
+		}
+	}
+}
+
 /**
  * cscfg_load_config_sets - API function to load feature and config sets.
  *
···
  * descriptors and load into the system.
  * Features are loaded first to ensure configuration dependencies can be met.
  *
+ * To facilitate dynamic loading and unloading, features and configurations
+ * have a "load_owner", to allow later unload by the same owner. An owner may
+ * be a loadable module or configuration dynamically created via configfs.
+ * As later loaded configurations can use earlier loaded features, creating load
+ * dependencies, a load order list is maintained. Unload is strictly in the
+ * reverse order to load.
+ *
  * @config_descs: 0 terminated array of configuration descriptors.
  * @feat_descs:   0 terminated array of feature descriptors.
+ * @owner_info:	  Information on the owner of this set.
  */
 int cscfg_load_config_sets(struct cscfg_config_desc **config_descs,
-			   struct cscfg_feature_desc **feat_descs)
+			   struct cscfg_feature_desc **feat_descs,
+			   struct cscfg_load_owner_info *owner_info)
 {
-	int err, i = 0;
+	int err = 0, i = 0;
 
 	mutex_lock(&cscfg_mutex);
 
···
 			if (err) {
 				pr_err("coresight-syscfg: Failed to load feature %s\n",
 				       feat_descs[i]->name);
+				cscfg_unload_owned_cfgs_feats(owner_info);
 				goto exit_unlock;
 			}
+			feat_descs[i]->load_owner = owner_info;
 			i++;
 		}
 	}
···
 			if (err) {
 				pr_err("coresight-syscfg: Failed to load configuration %s\n",
 				       config_descs[i]->name);
+				cscfg_unload_owned_cfgs_feats(owner_info);
 				goto exit_unlock;
 			}
+			config_descs[i]->load_owner = owner_info;
 			i++;
+		}
+	}
+
+	/* add the load owner to the load order list */
+	list_add_tail(&owner_info->item, &cscfg_mgr->load_order_list);
+	if (!list_is_singular(&cscfg_mgr->load_order_list)) {
+		/* lock previous item in load order list */
+		err = cscfg_owner_get(list_prev_entry(owner_info, item));
+		if (err) {
+			cscfg_unload_owned_cfgs_feats(owner_info);
+			list_del(&owner_info->item);
 		}
 	}
 
···
 	return err;
 }
 EXPORT_SYMBOL_GPL(cscfg_load_config_sets);
+
+/**
+ * cscfg_unload_config_sets - unload a set of configurations by owner.
+ *
+ * Dynamic unload of configuration and feature sets is done on the basis of
+ * the load owner of that set. Later loaded configurations can depend on
+ * features loaded earlier.
+ *
+ * Therefore, unload is only possible if:-
+ * 1) no configurations are active.
+ * 2) the set being unloaded was the last to be loaded to maintain dependencies.
+ *
+ * @owner_info:	Information on owner for set being unloaded.
+ */
+int cscfg_unload_config_sets(struct cscfg_load_owner_info *owner_info)
+{
+	int err = 0;
+	struct cscfg_load_owner_info *load_list_item = NULL;
+
+	mutex_lock(&cscfg_mutex);
+
+	/* cannot unload if anything is active */
+	if (atomic_read(&cscfg_mgr->sys_active_cnt)) {
+		err = -EBUSY;
+		goto exit_unlock;
+	}
+
+	/* cannot unload if not last loaded in load order */
+	if (!list_empty(&cscfg_mgr->load_order_list)) {
+		load_list_item = list_last_entry(&cscfg_mgr->load_order_list,
+						 struct cscfg_load_owner_info, item);
+		if (load_list_item != owner_info)
+			load_list_item = NULL;
+	}
+
+	if (!load_list_item) {
+		err = -EINVAL;
+		goto exit_unlock;
+	}
+
+	/* unload all belonging to load_owner */
+	cscfg_unload_owned_cfgs_feats(owner_info);
+
+	/* remove from load order list */
+	if (!list_is_singular(&cscfg_mgr->load_order_list)) {
+		/* unlock previous item in load order list */
+		cscfg_owner_put(list_prev_entry(owner_info, item));
+	}
+	list_del(&owner_info->item);
+
+exit_unlock:
+	mutex_unlock(&cscfg_mutex);
+	return err;
+}
+EXPORT_SYMBOL_GPL(cscfg_unload_config_sets);
 
 /* Handle coresight device registration and add configs and features to devices */
 
···
 }
 EXPORT_SYMBOL_GPL(cscfg_csdev_reset_feats);
 
-/**
- * cscfg_activate_config -  Mark a configuration descriptor as active.
- *
- * This will be seen when csdev devices are enabled in the system.
- * Only activated configurations can be enabled on individual devices.
- * Activation protects the configuration from alteration or removal while
- * active.
- *
- * Selection by hash value - generated from the configuration name when it
- * was loaded and added to the cs_etm/configurations file system for selection
- * by perf.
+/*
+ * This activate configuration for either perf or sysfs. Perf can have multiple
+ * active configs, selected per event, sysfs is limited to one.
  *
  * Increments the configuration descriptor active count and the global active
  * count.
  *
  * @cfg_hash: Hash value of the selected configuration name.
  */
-int cscfg_activate_config(unsigned long cfg_hash)
+static int _cscfg_activate_config(unsigned long cfg_hash)
 {
 	struct cscfg_config_desc *config_desc;
 	int err = -EINVAL;
 
-	mutex_lock(&cscfg_mutex);
-
 	list_for_each_entry(config_desc, &cscfg_mgr->config_desc_list, item) {
 		if ((unsigned long)config_desc->event_ea->var == cfg_hash) {
+			/* must ensure that config cannot be unloaded in use */
+			err = cscfg_owner_get(config_desc->load_owner);
+			if (err)
+				break;
 			/*
 			 * increment the global active count - control changes to
 			 * active configurations
···
 			break;
 		}
 	}
+	return err;
+}
+
+static void _cscfg_deactivate_config(unsigned long cfg_hash)
+{
+	struct cscfg_config_desc *config_desc;
+
+	list_for_each_entry(config_desc, &cscfg_mgr->config_desc_list, item) {
+		if ((unsigned long)config_desc->event_ea->var == cfg_hash) {
+			atomic_dec(&config_desc->active_cnt);
+			atomic_dec(&cscfg_mgr->sys_active_cnt);
+			cscfg_owner_put(config_desc->load_owner);
+			dev_dbg(cscfg_device(), "Deactivate config %s.\n", config_desc->name);
+			break;
+		}
+	}
+}
+
+/*
+ * called from configfs to set/clear the active configuration for use when
+ * using sysfs to control trace.
+ */
+int cscfg_config_sysfs_activate(struct cscfg_config_desc *config_desc, bool activate)
+{
+	unsigned long cfg_hash;
+	int err = 0;
+
+	mutex_lock(&cscfg_mutex);
+
+	cfg_hash = (unsigned long)config_desc->event_ea->var;
+
+	if (activate) {
+		/* cannot be a current active value to activate this */
+		if (cscfg_mgr->sysfs_active_config) {
+			err = -EBUSY;
+			goto exit_unlock;
+		}
+		err = _cscfg_activate_config(cfg_hash);
+		if (!err)
+			cscfg_mgr->sysfs_active_config = cfg_hash;
+	} else {
+		/* disable if matching current value */
+		if (cscfg_mgr->sysfs_active_config == cfg_hash) {
+			_cscfg_deactivate_config(cfg_hash);
+			cscfg_mgr->sysfs_active_config = 0;
+		} else
+			err = -EINVAL;
+	}
+
+exit_unlock:
+	mutex_unlock(&cscfg_mutex);
+	return err;
+}
+
+/* set the sysfs preset value */
+void cscfg_config_sysfs_set_preset(int preset)
+{
+	mutex_lock(&cscfg_mutex);
+	cscfg_mgr->sysfs_active_preset = preset;
+	mutex_unlock(&cscfg_mutex);
+}
+
+/*
+ * Used by a device to get the config and preset selected as active in configfs,
+ * when using sysfs to control trace.
+ */
+void cscfg_config_sysfs_get_active_cfg(unsigned long *cfg_hash, int *preset)
+{
+	mutex_lock(&cscfg_mutex);
+	*preset = cscfg_mgr->sysfs_active_preset;
+	*cfg_hash = cscfg_mgr->sysfs_active_config;
+	mutex_unlock(&cscfg_mutex);
+}
+EXPORT_SYMBOL_GPL(cscfg_config_sysfs_get_active_cfg);
+
+/**
+ * cscfg_activate_config -  Mark a configuration descriptor as active.
+ *
+ * This will be seen when csdev devices are enabled in the system.
+ * Only activated configurations can be enabled on individual devices.
+ * Activation protects the configuration from alteration or removal while
+ * active.
+ *
+ * Selection by hash value - generated from the configuration name when it
+ * was loaded and added to the cs_etm/configurations file system for selection
+ * by perf.
+ *
+ * @cfg_hash: Hash value of the selected configuration name.
+ */
+int cscfg_activate_config(unsigned long cfg_hash)
+{
+	int err = 0;
+
+	mutex_lock(&cscfg_mutex);
+	err = _cscfg_activate_config(cfg_hash);
 	mutex_unlock(&cscfg_mutex);
 
 	return err;
···
  */
 void cscfg_deactivate_config(unsigned long cfg_hash)
 {
-	struct cscfg_config_desc *config_desc;
-
 	mutex_lock(&cscfg_mutex);
-
-	list_for_each_entry(config_desc, &cscfg_mgr->config_desc_list, item) {
-		if ((unsigned long)config_desc->event_ea->var == cfg_hash) {
-			atomic_dec(&config_desc->active_cnt);
-			atomic_dec(&cscfg_mgr->sys_active_cnt);
-			dev_dbg(cscfg_device(), "Deactivate config %s.\n", config_desc->name);
-			break;
-		}
-	}
+	_cscfg_deactivate_config(cfg_hash);
 	mutex_unlock(&cscfg_mutex);
 }
 EXPORT_SYMBOL_GPL(cscfg_deactivate_config);
···
 	INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list);
 	INIT_LIST_HEAD(&cscfg_mgr->feat_desc_list);
 	INIT_LIST_HEAD(&cscfg_mgr->config_desc_list);
+	INIT_LIST_HEAD(&cscfg_mgr->load_order_list);
 	atomic_set(&cscfg_mgr->sys_active_cnt, 0);
 
 	/* preload built-in configurations */
-	err = cscfg_preload();
+	err = cscfg_preload(THIS_MODULE);
 	if (err)
 		goto exit_err;
 

drivers/hwtracing/coresight/coresight-syscfg.h

···
  * @csdev_desc_list:	List of coresight devices registered with the configuration manager.
  * @feat_desc_list:	List of feature descriptors to load into registered devices.
  * @config_desc_list:	List of system configuration descriptors to load into registered devices.
+ * @load_order_list:    Ordered list of owners for dynamically loaded configurations.
  * @sys_active_cnt:	Total number of active config descriptor references.
  * @cfgfs_subsys:	configfs subsystem used to manage configurations.
+ * @sysfs_active_config:Active config hash used if CoreSight controlled from sysfs.
+ * @sysfs_active_preset:Active preset index used if CoreSight controlled from sysfs.
  */
 struct cscfg_manager {
 	struct device dev;
 	struct list_head csdev_desc_list;
 	struct list_head feat_desc_list;
 	struct list_head config_desc_list;
+	struct list_head load_order_list;
 	atomic_t sys_active_cnt;
 	struct configfs_subsystem cfgfs_subsys;
+	u32 sysfs_active_config;
+	int sysfs_active_preset;
 };
 
 /* get reference to dev in cscfg_manager */
···
 	struct list_head item;
 };
 
+/* owner types for loading and unloading of config and feature sets */
+enum cscfg_load_owner_type {
+	CSCFG_OWNER_PRELOAD,
+	CSCFG_OWNER_MODULE,
+};
+
+/**
+ * Load item - item to add to the load order list allowing dynamic load and
+ *             unload of configurations and features. Caller loading a config
+ *	       set provides a context handle for unload. API ensures that
+ *	       items unloaded strictly in reverse order from load to ensure
+ *	       dependencies are respected.
+ *
+ * @item:		list entry for load order list.
+ * @type:		type of owner - allows interpretation of owner_handle.
+ * @owner_handle:	load context - handle for owner of loaded configs.
+ */
+struct cscfg_load_owner_info {
+	struct list_head item;
+	int type;
+	void *owner_handle;
+};
+
 /* internal core operations for cscfg */
 int __init cscfg_init(void);
 void cscfg_exit(void);
-int cscfg_preload(void);
+int cscfg_preload(void *owner_handle);
 const struct cscfg_feature_desc *cscfg_get_named_feat_desc(const char *name);
 int cscfg_update_feat_param_val(struct cscfg_feature_desc *feat_desc,
 				int param_idx, u64 value);
-
+int cscfg_config_sysfs_activate(struct cscfg_config_desc *cfg_desc, bool activate);
+void cscfg_config_sysfs_set_preset(int preset);
 
 /* syscfg manager external API */
 int cscfg_load_config_sets(struct cscfg_config_desc **cfg_descs,
-			   struct cscfg_feature_desc **feat_descs);
+			   struct cscfg_feature_desc **feat_descs,
+			   struct cscfg_load_owner_info *owner_info);
+int cscfg_unload_config_sets(struct cscfg_load_owner_info *owner_info);
 int cscfg_register_csdev(struct coresight_device *csdev, u32 match_flags,
 			 struct cscfg_csdev_feat_ops *ops);
 void cscfg_unregister_csdev(struct coresight_device *csdev);
···
 int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
 				     unsigned long cfg_hash, int preset);
 void cscfg_csdev_disable_active_config(struct coresight_device *csdev);
+void cscfg_config_sysfs_get_active_cfg(unsigned long *cfg_hash, int *preset);
 
 #endif /* CORESIGHT_SYSCFG_H */

samples/Kconfig

···
 	  Build example userspace program to use the new mount_notify(),
 	  sb_notify() syscalls and the KEYCTL_WATCH_KEY keyctl() function.
 
+config SAMPLE_CORESIGHT_SYSCFG
+	tristate "Build example loadable module for CoreSight config"
+	depends on CORESIGHT && m
+	help
+	  Build an example loadable module that adds new CoreSight features
+	  and configuration using the CoreSight system configuration API.
+	  This demonstrates how a user may create their own CoreSight
+	  configurations and easily load them into the system at runtime.
+
 endif # SAMPLES
 
 config HAVE_SAMPLE_FTRACE_DIRECT

samples/Makefile

···
 subdir-$(CONFIG_SAMPLE_WATCHDOG)	+= watchdog
 subdir-$(CONFIG_SAMPLE_WATCH_QUEUE)	+= watch_queue
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST)	+= kmemleak/
+obj-$(CONFIG_SAMPLE_CORESIGHT_SYSCFG)	+= coresight/

samples/coresight/Makefile

···
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_SAMPLE_CORESIGHT_SYSCFG) += coresight-cfg-sample.o
+ccflags-y += -I$(srctree)/drivers/hwtracing/coresight

samples/coresight/coresight-cfg-sample.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright(C) 2020 Linaro Limited. All rights reserved.
+ * Author: Mike Leach <[e-mail]>
+ */
+
+#include "coresight-config.h"
+#include "coresight-syscfg.h"
+
+/* create an alternate autofdo configuration */
+
+/* we will provide 4 sets of preset parameter values */
+#define AFDO2_NR_PRESETS	4
+/* the total number of parameters in used features - strobing has 2 */
+#define AFDO2_NR_PARAM_SUM	2
+
+static const char *afdo2_ref_names[] = {
+	"strobing",
+};
+
+/*
+ * set of presets leaves strobing window constant while varying period to allow
+ * experimentation with mark / space ratios for various workloads
+ */
+static u64 afdo2_presets[AFDO2_NR_PRESETS][AFDO2_NR_PARAM_SUM] = {
+	{ 1000, 100 },
+	{ 1000, 1000 },
+	{ 1000, 5000 },
+	{ 1000, 10000 },
+};
+
+struct cscfg_config_desc afdo2 = {
+	.name = "autofdo2",
+	.description = "Setup ETMs with strobing for autofdo\n"
+	"Supplied presets allow experimentation with mark-space ratio for various loads\n",
+	.nr_feat_refs = ARRAY_SIZE(afdo2_ref_names),
+	.feat_ref_names = afdo2_ref_names,
+	.nr_presets = AFDO2_NR_PRESETS,
+	.nr_total_params = AFDO2_NR_PARAM_SUM,
+	.presets = &afdo2_presets[0][0],
+};
+
+static struct cscfg_feature_desc *sample_feats[] = {
+	NULL
+};
+
+static struct cscfg_config_desc *sample_cfgs[] = {
+	&afdo2,
+	NULL
+};
+
+static struct cscfg_load_owner_info mod_owner = {
+	.type = CSCFG_OWNER_MODULE,
+	.owner_handle = THIS_MODULE,
+};
+
+/* module init and exit - just load and unload configs */
+static int __init cscfg_sample_init(void)
+{
+	return cscfg_load_config_sets(sample_cfgs, sample_feats, &mod_owner);
+}
+
+static void __exit cscfg_sample_exit(void)
+{
+	cscfg_unload_config_sets(&mod_owner);
+}
+
+module_init(cscfg_sample_init);
+module_exit(cscfg_sample_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Mike Leach <[e-mail]>");
+MODULE_DESCRIPTION("CoreSight Syscfg Example");