[...]
> > +
> > +/**
> > + * Mark a config descriptor as active.
> > + * This will be seen when csdev devices are activated in the system.
> > + *
> > + * 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)
> > +{
> > + struct cscfg_config_desc *curr_item, *match_item = 0;
> > +
> > + mutex_lock(&cscfg_mutex);
> > +
> > + list_for_each_entry(curr_item, &cscfg_mgr->data.config_desc_list, item) {
> > + if ((unsigned long)curr_item->id_ea->var == cfg_hash) {
> > + match_item = curr_item;
> > + atomic_inc(&cscfg_mgr->data.sys_active_cnt);
>
> It would be nice to have a comment that mentions why this is needed. I had to
> go look in patch 09 to see that it prevents a feature from being changed when
> any configuration is active. And since patch 09 is the only place where
> @sys_active_cnt is used, please move the declaration and handling of the
> variable there.
>
> > + break;
> > + }
> > + }
> > + mutex_unlock(&cscfg_mutex);
> > +
> > + if (!match_item)
> > + return -EINVAL;
> > +
> > + dev_dbg(to_device_cscfg(), "Activate config %s.\n", match_item->name);
> > +
> > + /* mark the descriptors as active so enable config will use them */
> > + mutex_lock(&cscfg_csdev_mutex);
> > + atomic_inc(&match_item->active_cnt);
>
> What is ->active_cnt used for? I see it referenced in
> cscfg_csdev_enable_active_config() but it doesn't do much other than to confirm
> the configuration has been activated by someone.
>
> There is also a chance that a caller would call cscfg_activate_config() once and
> call cscfg_csdev_enable_active_config() multiple time, which would really create
> problems. I would move the incrementation of sys_active_cnt within the mutex
> hold in cscfg_csdev_enable_active_config() and get rid of ->active_cnt. If I am
> correct we wouldn't need cscfg_activate_config() after that.
>
I looked at patch 06 and I understand why incrementing sys_active_cnt has to be
done before enabling it. If it wasn't so someone could update the feature
between the time setup_aux() is called and the event is installed on a CPU. As
such cscfg_activate_config() should stay but I still think ->active_cnt should
go.
> > + mutex_unlock(&cscfg_csdev_mutex);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_activate_config);
> > +
> > +void cscfg_deactivate_config(unsigned long cfg_hash)
>
> I'm fine with either cfg_hash or id_hash, but not both.
>
> > +{
> > + struct cscfg_config_desc *curr_item, *match_item = 0;
> > +
> > + mutex_lock(&cscfg_mutex);
> > +
> > + list_for_each_entry(curr_item, &cscfg_mgr->data.config_desc_list, item) {
> > + if ((unsigned long)curr_item->id_ea->var == cfg_hash) {
> > + match_item = curr_item;
> > + break;
> > + }
> > + }
> > + mutex_unlock(&cscfg_mutex);
> > + if (!match_item)
> > + return;
> > +
> > + dev_dbg(to_device_cscfg(), "Deactivate config %s.\n", match_item->name);
> > +
> > + mutex_lock(&cscfg_csdev_mutex);
> > + atomic_dec(&match_item->active_cnt);
> > + mutex_unlock(&cscfg_csdev_mutex);
> > +
> > + atomic_dec(&cscfg_mgr->data.sys_active_cnt);
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_deactivate_config);
> > +
> > +/* Find and program any active config for the supplied device.*/
> > +int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
> > + unsigned long id_hash, int preset)
> > +{
> > + struct cscfg_config_csdev *cfg = NULL, *item;
> > + const struct cscfg_config_desc *desc;
> > + int err = 0;
> > +
> > + /* quickly check global count */
> > + if (!atomic_read(&cscfg_mgr->data.sys_active_cnt))
> > + return 0;
> > +
> > + mutex_lock(&cscfg_csdev_mutex);
> > + list_for_each_entry(item, &csdev->config_csdev_list, node) {
> > + desc = item->desc;
> > + if ((atomic_read(&desc->active_cnt)) &&
> > + ((unsigned long)desc->id_ea->var == id_hash)) {
> > + cfg = item;
> > + break;
> > + }
> > + }
> > + if (cfg) {
> > + err = cscfg_csdev_enable_config(cfg, preset);
> > + if (!err)
> > + csdev->active_cfg_ctxt = (void *)cfg;
> > + }
> > + mutex_unlock(&cscfg_csdev_mutex);
> > + return err;
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_csdev_enable_active_config);
> > +
> > +/* save and disable the active config for the device */
> > +void cscfg_csdev_disable_active_config(struct coresight_device *csdev)
> > +{
> > + struct cscfg_config_csdev *cfg;
> > +
> > + mutex_lock(&cscfg_csdev_mutex);
> > + cfg = (struct cscfg_config_csdev *)csdev->active_cfg_ctxt;
> > + if (cfg)
> > + cscfg_csdev_disable_config(cfg);
> > + mutex_unlock(&cscfg_csdev_mutex);
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_csdev_disable_active_config);
> > +
> > /* Initialise system configuration management device. */
> >
> > struct device *to_device_cscfg(void)
> > @@ -546,6 +672,7 @@ int __init cscfg_init(void)
> > INIT_LIST_HEAD(&cscfg_mgr->data.feat_desc_list);
> > INIT_LIST_HEAD(&cscfg_mgr->data.config_desc_list);
> > cscfg_mgr->data.nr_csdev = 0;
> > + atomic_set(&cscfg_mgr->data.sys_active_cnt, 0);
> >
> > dev_info(to_device_cscfg(), "CoreSight Configuration manager initialised");
> > return 0;
> > diff --git a/drivers/hwtracing/coresight/coresight-syscfg.h b/drivers/hwtracing/coresight/coresight-syscfg.h
> > index ebf5e1491d86..301e26e1e98f 100644
> > --- a/drivers/hwtracing/coresight/coresight-syscfg.h
> > +++ b/drivers/hwtracing/coresight/coresight-syscfg.h
> > @@ -17,13 +17,15 @@
> > * @csdev_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.
> > - * @nr_csdev: Number of registered devices with the cscfg system
> > + * @nr_csdev: Number of registered devices with the cscfg system
> > + * @sys_active_cnt: Total number of active config descriptor references.
> > */
> > struct cscfg_api_data {
> > struct list_head csdev_desc_list;
> > struct list_head feat_desc_list;
> > struct list_head config_desc_list;
> > int nr_csdev;
> > + atomic_t sys_active_cnt;
> > };
> >
> > /**
> > @@ -53,6 +55,12 @@ int cscfg_register_csdev(struct coresight_device *csdev,
> > struct cscfg_match_desc *info,
> > struct cscfg_csdev_feat_ops *ops);
> > void cscfg_unregister_csdev(struct coresight_device *csdev);
> > +int cscfg_activate_config(unsigned long cfg_hash);
> > +void cscfg_deactivate_config(unsigned long cfg_hash);
> > +void cscfg_csdev_reset_feats(struct coresight_device *csdev);
> > +int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
> > + unsigned long id_hash, int preset);
> > +void cscfg_csdev_disable_active_config(struct coresight_device *csdev);
> >
> > /**
> > * System configuration manager device.
> > diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> > index d0126ed326a6..3941854e8280 100644
> > --- a/include/linux/coresight.h
> > +++ b/include/linux/coresight.h
> > @@ -221,6 +221,7 @@ struct coresight_sysfs_link {
> > * @has_conns_grp: Have added a "connections" group for sysfs links.
> > * @feature_csdev_list: List of complex feature programming added to the device.
> > * @config_csdev_list: List of system configurations added to the device.
> > + * @active_cfg_ctxt: Context information for current active congfig.
> > */
> > struct coresight_device {
> > struct coresight_platform_data *pdata;
> > @@ -245,6 +246,7 @@ struct coresight_device {
> > /* system configuration and feature lists */
> > struct list_head feature_csdev_list;
> > struct list_head config_csdev_list;
> > + void *active_cfg_ctxt;
> > };
> >
> > /*
> > --
> > 2.17.1
> >
