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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>,
        Mathieu Poirier <mathieu.poirier@linaro.org>
Cc:     Branislav Rankov <branislav.rankov@arm.com>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Coresight ML <coresight@lists.linaro.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Yabin Cui <yabinc@google.com>, Jon Corbet <corbet@lwn.net>,
        Leo Yan <leo.yan@linaro.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Tingwei Zhang <tingwei@codeaurora.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        nd <nd@arm.com>
References: <20210414191903.18349-1-mike.leach@linaro.org>
 <20210414191903.18349-6-mike.leach@linaro.org>
 <dfbb1acf-b174-1990-33d3-39e2ab746959@arm.com>
 <CANLsYkyR-kUO7CiK4vuw+DNFMxCCsLN24s3mZ2Uw4vAq5aPD3g@mail.gmail.com>
 <CAJ9a7Vjsmu88ZY1h11o13VMu9C9gaBr_8HEmSa5iAH3NvwM=NA@mail.gmail.com>
From:   Suzuki K Poulose <suzuki.poulose@arm.com>
Message-ID: <815e1569-7e46-7891-4982-f3d38d734658@arm.com>
Date:   Fri, 25 Jun 2021 16:09:16 +0100
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On 25/06/2021 15:37, Mike Leach wrote:
> HI Branislav, Mathieu,
> 
> I have started to look into this as a top priority.
> 
> However, when I enable the CONFIG_DEBUG_ option my board fails to boot
> at all. (Dragonboard DB410c), so the resolution make take a little
> time.
> 
> At this point I am assuming that the mutex will need to be replaced by
> a spinlock - so a re-design + v8 set may well be required.

Or may be a refcount on the "config" instance may work too ?
i.e, when the config is loaded onto a device, a refcount could be
taken on the config and dropped on unload.

Whoever drops it to zero could release it.

Thoughts ?

Suzuki


> 
> Regards
> 
> Mike
> 
> On Mon, 14 Jun 2021 at 18:03, Mathieu Poirier
> <mathieu.poirier@linaro.org> wrote:
>>
>> Hi Branislav,
>>
>> On Thu, 10 Jun 2021 at 05:05, Branislav Rankov <branislav.rankov@arm.com> wrote:
>>>
>>>
>>> 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.
>>
>> Thanks for reporting this.  Unfortunately Mike is away and likely
>> won't be able to look at this in time for the merge window.  As such I
>> backed out the complex configuration feature from the next branch but
>> that code is still available on next-complex-configuration.
>>
>> Thanks,
>> Mathieu
>>
>>>
>>> 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;
>>>>    };
>>>>
>>>>    /*
>>>>
> 
> 
>