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Subject: Re: [PATCH v7 05/10] coresight: syscfg: Add API to activate and
 enable configurations
To:     Mike Leach <mike.leach@linaro.org>,
        linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org,
        mathieu.poirier@linaro.org, linux-doc@vger.kernel.org,
        suzuki.poulose@arm.com
Cc:     yabinc@google.com, corbet@lwn.net, leo.yan@linaro.org,
        alexander.shishkin@linux.intel.com, tingwei@codeaurora.org,
        gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        nd@arm.com
References: <20210414191903.18349-1-mike.leach@linaro.org>
 <20210414191903.18349-6-mike.leach@linaro.org>
From:   Branislav Rankov <branislav.rankov@arm.com>
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Date:   Thu, 10 Jun 2021 12:05:09 +0100
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On 4/14/21 8:18 PM, 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>
> Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>   .../hwtracing/coresight/coresight-config.h    |   2 +
>   .../hwtracing/coresight/coresight-syscfg.c    | 172 ++++++++++++++++++
>   .../hwtracing/coresight/coresight-syscfg.h    |   8 +
>   include/linux/coresight.h                     |   2 +
>   4 files changed, 184 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 e35f8c0ac2f8..b234e45c153f 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -283,6 +283,7 @@ 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 +469,176 @@ 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;
> +
> +	mutex_lock(&cscfg_csdev_mutex);
> +	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:
> +	mutex_unlock(&cscfg_csdev_mutex);
> +}
> +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;
> +	int err = 0;
> +
> +	/* quickly check global count */
> +	if (!atomic_read(&cscfg_mgr->sys_active_cnt))
> +		return 0;
> +
> +	mutex_lock(&cscfg_csdev_mutex);
> +	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;
> +			break;
> +		}
> +	}
> +	if (config_csdev_active) {
> +		err = cscfg_csdev_enable_config(config_csdev_active, preset);
> +		if (!err)
> +			csdev->active_cscfg_ctxt = (void *)config_csdev_active;
> +	}
> +	mutex_unlock(&cscfg_csdev_mutex);
> +	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;
> +
> +	mutex_lock(&cscfg_csdev_mutex);

This line seems to cause a bug report when the kernel is compiled with CONFIG_DEBUG_ATOMIC_SLEEP=y

I have tested this by applying the series to 5.10 kernel on Dragonboard 845c.

It only happens when strobing is used.

The report is this:

[13431.885395] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:283
[13431.893919] in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 3525, name: perf
[13431.901882] CPU: 0 PID: 3525 Comm: perf Tainted: G        W         5.10.0-rc5-17282-g923b456a55fb #124
[13431.911436] Hardware name: Thundercomm Dragonboard 845c (DT)
[13431.917450] Call trace:
[13431.919938]  dump_backtrace+0x0/0x1a0
[13431.923644]  show_stack+0x18/0x68
[13431.927008]  dump_stack+0xd0/0x12c
[13431.930444]  ___might_sleep+0xf0/0x130
[13431.934228]  __might_sleep+0x54/0x90
[13431.937945]  mutex_lock+0x28/0x80
[13431.941468]  cscfg_csdev_disable_active_config+0x24/0x50
[13431.946952]  etm4_disable+0xf0/0x100
[13431.950571]  etm_event_stop+0xb8/0x130
[13431.954380]  etm_event_del+0x14/0x20
[13431.958008]  event_sched_out.isra.0+0x84/0x1c8
[13431.962496]  group_sched_out.part.0+0x44/0xc8
[13431.967010]  __perf_event_disable+0xe4/0x198
[13431.971549]  event_function+0x8c/0xe8
[13431.975256]  remote_function+0x64/0x78
[13431.979161]  generic_exec_single+0xa0/0x100
[13431.983876]  smp_call_function_single+0x158/0x1d8
[13431.988629]  event_function_call+0x128/0x138
[13431.992942]  _perf_event_disable+0x48/0x70
[13431.997082]  perf_event_for_each_child+0x3c/0x90
[13432.001751]  _perf_ioctl+0x198/0x4a8
[13432.005359]  perf_ioctl+0x4c/0x78
[13432.008715]  __arm64_sys_ioctl+0xa8/0xf0
[13432.012835]  el0_svc_common.constprop.0+0x78/0x1a0
[13432.017767]  do_el0_svc+0x24/0x90
[13432.021616]  el0_sync_handler+0x160/0x168
[13432.025670]  el0_sync+0x174/0x180


> +	config_csdev = (struct cscfg_config_csdev *)csdev->active_cscfg_ctxt;
> +	if (config_csdev) {
> +		cscfg_csdev_disable_config(config_csdev);
> +		csdev->active_cscfg_ctxt = NULL;
> +	}
> +	mutex_unlock(&cscfg_csdev_mutex);
> +}
> +EXPORT_SYMBOL_GPL(cscfg_csdev_disable_active_config);
> +
>   /* Initialise system configuration management device. */
>   
>   struct device *cscfg_device(void)
> @@ -536,6 +707,7 @@ 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 6fb516e1b22e..a348049ee08b 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -222,6 +222,7 @@ 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_cscfg_ctxt:  Context information for current active system configuration.
>    */
>   struct coresight_device {
>   	struct coresight_platform_data *pdata;
> @@ -246,6 +247,7 @@ struct coresight_device {
>   	/* system configuration and feature lists */
>   	struct list_head feature_csdev_list;
>   	struct list_head config_csdev_list;
> +	void *active_cscfg_ctxt;
>   };
>   
>   /*
>