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

From: Mathieu Poirier
Date: Wed Jul 28 2021 - 12:24:18 EST

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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.

> + 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.
*/

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
>

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