Re: [PATCH v9 05/10] coresight: syscfg: Add API to activate and enable configurations

[Mike Leach]

Hi Mathieu,

On Wed, 28 Jul 2021 at 17:24, Mathieu Poirier
<mathieu.poirier@xxxxxxxxxx> wrote:
>
> On Fri, Jul 23, 2021 at 05:54:39PM +0100, 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@xxxxxxxxxx>
> > ---
> >  .../hwtracing/coresight/coresight-config.h    |   2 +
> >  .../hwtracing/coresight/coresight-syscfg.c    | 212 ++++++++++++++++++
> >  .../hwtracing/coresight/coresight-syscfg.h    |   8 +
> >  include/linux/coresight.h                     |   2 +
> >  4 files changed, 224 insertions(+)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-config.h b/drivers/hwtracing/coresight/coresight-config.h
> > index 0667581822c1..25eb6c632692 100644
> > --- a/drivers/hwtracing/coresight/coresight-config.h
> > +++ b/drivers/hwtracing/coresight/coresight-config.h
> > @@ -127,6 +127,7 @@ struct cscfg_feature_desc {
> >   * @nr_total_params: Sum of all parameters declared by used features
> >   * @presets:         Array of preset values.
> >   * @event_ea:                Extended attribute for perf event value
> > + * @active_cnt:              ref count for activate on this configuration.
> >   *
> >   */
> >  struct cscfg_config_desc {
> > @@ -139,6 +140,7 @@ struct cscfg_config_desc {
> >       int nr_total_params;
> >       const u64 *presets; /* nr_presets * nr_total_params */
> >       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 b93f2b4a777e..8903aab36c51 100644
> > --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> > +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> > @@ -282,6 +282,7 @@ static int cscfg_load_config(struct cscfg_config_desc *config_desc)
> >               return err;
> >
> >       list_add(&config_desc->item, &cscfg_mgr->config_desc_list);
> > +     atomic_set(&config_desc->active_cnt, 0);
> >       return 0;
> >  }
> >
> > @@ -468,6 +469,216 @@ void cscfg_unregister_csdev(struct coresight_device *csdev)
> >  }
> >  EXPORT_SYMBOL_GPL(cscfg_unregister_csdev);
> >
> > +/**
> > + * cscfg_csdev_reset_feats - reset features for a CoreSight device.
> > + *
> > + * Resets all parameters and register values for any features loaded
> > + * into @csdev to their default values.
> > + *
> > + * @csdev: The CoreSight device.
> > + */
> > +void cscfg_csdev_reset_feats(struct coresight_device *csdev)
> > +{
> > +     struct cscfg_feature_csdev *feat_csdev;
> > +     unsigned long flags;
> > +
> > +     spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> > +     if (list_empty(&csdev->feature_csdev_list))
> > +             goto unlock_exit;
> > +
> > +     list_for_each_entry(feat_csdev, &csdev->feature_csdev_list, node)
> > +             cscfg_reset_feat(feat_csdev);
> > +
> > +unlock_exit:
> > +     spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> > +}
> > +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.
> > + *
> > + * 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)
> > +{
> > +     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) {
> > +                     /*
> > +                      * increment the global active count - control changes to
> > +                      * active configurations
> > +                      */
> > +                     atomic_inc(&cscfg_mgr->sys_active_cnt);
> > +
> > +                     /*
> > +                      * mark the descriptor as active so enable config on a
> > +                      * device instance will use it
> > +                      */
> > +                     atomic_inc(&config_desc->active_cnt);
> > +
> > +                     err = 0;
> > +                     dev_dbg(cscfg_device(), "Activate config %s.\n", config_desc->name);
> > +                     break;
> > +             }
> > +     }
> > +     mutex_unlock(&cscfg_mutex);
> > +
> > +     return err;
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_activate_config);
> > +
> > +/**
> > + * cscfg_deactivate_config -  Mark a config descriptor as inactive.
> > + *
> > + * Decrement the configuration and global active counts.
> > + *
> > + * @cfg_hash: Hash value of the selected configuration name.
> > + */
> > +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;
> > +             }
> > +     }
> > +     mutex_unlock(&cscfg_mutex);
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_deactivate_config);
> > +
> > +/**
> > + * cscfg_csdev_enable_active_config - Enable matching active configuration for device.
> > + *
> > + * Enables the configuration selected by @cfg_hash if the configuration is supported
> > + * on the device and has been activated.
> > + *
> > + * If active and supported the CoreSight device @csdev will be programmed with the
> > + * configuration, using @preset parameters.
> > + *
> > + * Should be called before driver hardware enable for the requested device, prior to
> > + * programming and enabling the physical hardware.
> > + *
> > + * @csdev:   CoreSight device to program.
> > + * @cfg_hash:        Selector for the configuration.
> > + * @preset:  Preset parameter values to use, 0 for current / default values.
> > + */
> > +int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
> > +                                  unsigned long cfg_hash, int preset)
> > +{
> > +     struct cscfg_config_csdev *config_csdev_active = NULL, *config_csdev_item;
> > +     const struct cscfg_config_desc *config_desc;
> > +     unsigned long flags;
> > +     int err = 0;
> > +
> > +     /* quickly check global count */
> > +     if (!atomic_read(&cscfg_mgr->sys_active_cnt))
> > +             return 0;
> > +
> > +     /* look for matching config - set in_enable flag if found */
>
> The second part of this comment no longer applies.
>

You are right - sorry missed that!

> > +     spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> > +     list_for_each_entry(config_csdev_item, &csdev->config_csdev_list, node) {
> > +             config_desc = config_csdev_item->config_desc;
> > +             if ((atomic_read(&config_desc->active_cnt)) &&
> > +                 ((unsigned long)config_desc->event_ea->var == cfg_hash)) {
> > +                     config_csdev_active = config_csdev_item;
> > +                     csdev->active_cscfg_ctxt = (void *)config_csdev_active;
> > +                     break;
> > +             }
> > +     }
> > +     spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> > +
> > +     /*
> > +      * If found, attempt to enable
> > +      */
> > +     if (config_csdev_active) {
> > +             /*
> > +              * Call the generic routine that will program up the internal
> > +              * driver structures prior to programming up the hardware.
> > +              * This routine takes the driver spinlock saved in the configs.
> > +              */
> > +             err = cscfg_csdev_enable_config(config_csdev_active, preset);
> > +             if (!err) {
> > +                     /*
> > +                      * Successful programming. Check the active_cscfg_ctxt
> > +                      * pointer to ensure no pre-emption disabled it via
> > +                      * cscfg_csdev_disable_active_config() before
> > +                      * we could start.
> > +                      *
> > +                      * Set enabled if OK, err if not.
> > +                      */
> > +                     spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> > +                     if (csdev->active_cscfg_ctxt)
> > +                             config_csdev_active->enabled = true;
> > +                     else
> > +                             err = -EBUSY;
> > +                     spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> > +             }
>
> This is much better.  I spent some time trying to break the heuristic and I
> can't.  I intend to re-apply this set to give it as much exposure as possible but
> want to see the above comment fixed.  I will do that locally though to avoid
> having to deal with another revision.  What do you think of:
>
>         /*
>          * Look for a matching configuration - set the active configuration
>          * context if found.
>          */
>

That looks fin to me

Thanks

Mike


> Thanks,
> Mathieu
>
> > +     }
> > +     return err;
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_csdev_enable_active_config);
> > +
> > +/**
> > + * cscfg_csdev_disable_active_config - disable an active config on the device.
> > + *
> > + * Disables the active configuration on the CoreSight device @csdev.
> > + * Disable will save the values of any registers marked in the configurations
> > + * as save on disable.
> > + *
> > + * Should be called after driver hardware disable for the requested device,
> > + * after disabling the physical hardware and reading back registers.
> > + *
> > + * @csdev: The CoreSight device.
> > + */
> > +void cscfg_csdev_disable_active_config(struct coresight_device *csdev)
> > +{
> > +     struct cscfg_config_csdev *config_csdev;
> > +     unsigned long flags;
> > +
> > +     /*
> > +      * Check if we have an active config, and that it was successfully enabled.
> > +      * If it was not enabled, we have no work to do, otherwise mark as disabled.
> > +      * Clear the active config pointer.
> > +      */
> > +     spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> > +     config_csdev = (struct cscfg_config_csdev *)csdev->active_cscfg_ctxt;
> > +     if (config_csdev) {
> > +             if (!config_csdev->enabled)
> > +                     config_csdev = NULL;
> > +             else
> > +                     config_csdev->enabled = false;
> > +     }
> > +     csdev->active_cscfg_ctxt = NULL;
> > +     spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> > +
> > +     /* true if there was an enabled active config */
> > +     if (config_csdev)
> > +             cscfg_csdev_disable_config(config_csdev);
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_csdev_disable_active_config);
> > +
> >  /* Initialise system configuration management device. */
> >
> >  struct device *cscfg_device(void)
> > @@ -536,6 +747,7 @@ int __init cscfg_init(void)
> >       INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list);
> >       INIT_LIST_HEAD(&cscfg_mgr->feat_desc_list);
> >       INIT_LIST_HEAD(&cscfg_mgr->config_desc_list);
> > +     atomic_set(&cscfg_mgr->sys_active_cnt, 0);
> >
> >       dev_info(cscfg_device(), "CoreSight Configuration manager initialised");
> >       return 0;
> > diff --git a/drivers/hwtracing/coresight/coresight-syscfg.h b/drivers/hwtracing/coresight/coresight-syscfg.h
> > index 5bcae3b374c6..a52775890670 100644
> > --- a/drivers/hwtracing/coresight/coresight-syscfg.h
> > +++ b/drivers/hwtracing/coresight/coresight-syscfg.h
> > @@ -24,12 +24,14 @@
> >   * @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.
> > + * @sys_active_cnt:  Total number of active config descriptor references.
> >   */
> >  struct cscfg_manager {
> >       struct device dev;
> >       struct list_head csdev_desc_list;
> >       struct list_head feat_desc_list;
> >       struct list_head config_desc_list;
> > +     atomic_t sys_active_cnt;
> >  };
> >
> >  /* get reference to dev in cscfg_manager */
> > @@ -61,5 +63,11 @@ int cscfg_load_config_sets(struct cscfg_config_desc **cfg_descs,
> >  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_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 cfg_hash, int preset);
> > +void cscfg_csdev_disable_active_config(struct coresight_device *csdev);
> >
> >  #endif /* CORESIGHT_SYSCFG_H */
> > diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> > index 16544ae2b532..93a2922b7653 100644
> > --- a/include/linux/coresight.h
> > +++ b/include/linux/coresight.h
> > @@ -223,6 +223,7 @@ struct coresight_sysfs_link {
> >   * @feature_csdev_list: List of complex feature programming added to the device.
> >   * @config_csdev_list:  List of system configurations added to the device.
> >   * @cscfg_csdev_lock:        Protect the lists of configurations and features.
> > + * @active_cscfg_ctxt:  Context information for current active system configuration.
> >   */
> >  struct coresight_device {
> >       struct coresight_platform_data *pdata;
> > @@ -248,6 +249,7 @@ struct coresight_device {
> >       struct list_head feature_csdev_list;
> >       struct list_head config_csdev_list;
> >       spinlock_t cscfg_csdev_lock;
> > +     void *active_cscfg_ctxt;
> >  };
> >
> >  /*
> > --
> > 2.17.1
> >



-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK