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    SubjectRe: [PATCH v4 05/10] coresight: syscfg: Add API to activate and enable configurations
    On Thu, Jan 28, 2021 at 05:09:31PM +0000, Mike Leach wrote:
    > Configurations are first activated, then when any coresight device is
    > enabled, the active configurations are checked and any matching
    > one is enabled.
    >
    > This patch provides the activation / enable API.
    >
    > Signed-off-by: Mike Leach <mike.leach@linaro.org>
    > ---
    > .../hwtracing/coresight/coresight-config.h | 2 +
    > .../hwtracing/coresight/coresight-syscfg.c | 127 ++++++++++++++++++
    > .../hwtracing/coresight/coresight-syscfg.h | 10 +-
    > include/linux/coresight.h | 2 +
    > 4 files changed, 140 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/hwtracing/coresight/coresight-config.h b/drivers/hwtracing/coresight/coresight-config.h
    > index 98380b496046..26396b70c826 100644
    > --- a/drivers/hwtracing/coresight/coresight-config.h
    > +++ b/drivers/hwtracing/coresight/coresight-config.h
    > @@ -156,6 +156,7 @@ struct cscfg_config_feat_ref {
    > * @presets: Array of preset values.
    > * @id_ea: Extended attribute for perf configid value
    > * @event_ea: Extended attribute for perf event value
    > + * @active_cnt: ref count for activate on this configuration.
    > */
    > struct cscfg_config_desc {
    > const char *name;
    > @@ -168,6 +169,7 @@ struct cscfg_config_desc {
    > const u64 *presets; /* nr_presets * nr_total_params */
    > struct dev_ext_attribute *id_ea;
    > struct dev_ext_attribute *event_ea;
    > + atomic_t active_cnt;
    > };
    >
    > /**
    > diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
    > index a070f135eca3..d79cf5b36758 100644
    > --- a/drivers/hwtracing/coresight/coresight-syscfg.c
    > +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
    > @@ -298,6 +298,7 @@ static int cscfg_load_config(struct cscfg_config_desc *cfg_desc)
    > return err;
    >
    > list_add(&cfg_desc->item, &cscfg_mgr->data.config_desc_list);
    > + atomic_set(&cfg_desc->active_cnt, 0);
    > return 0;
    > }
    >
    > @@ -477,6 +478,131 @@ void cscfg_unregister_csdev(struct coresight_device *csdev)
    > }
    > EXPORT_SYMBOL_GPL(cscfg_unregister_csdev);
    >
    > +void cscfg_csdev_reset_feats(struct coresight_device *csdev)
    > +{
    > + struct cscfg_feature_csdev *feat;
    > +
    > + mutex_lock(&cscfg_csdev_mutex);
    > + if (list_empty(&csdev->feature_csdev_list))
    > + goto unlock_exit;
    > +
    > + list_for_each_entry(feat, &csdev->feature_csdev_list, node)
    > + cscfg_reset_feat(feat);
    > +
    > +unlock_exit:
    > + mutex_unlock(&cscfg_csdev_mutex);
    > +}
    > +EXPORT_SYMBOL_GPL(cscfg_csdev_reset_feats);
    > +
    > +/**
    > + * 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.

    > + 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
    >

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