Re: [PATCH v8 2/8] coresight: core: add a new API to retrieve the helper device

[Jie Gan <jie.gan@oss.qualcomm.com>]

On 12/19/2025 1:50 AM, Suzuki K Poulose wrote:
> On 11/12/2025 06:10, Jie Gan wrote:
>> Retrieving the helper device of the specific coresight device based on
>> its helper_subtype because a single coresight device may has multiple 
>> types
>> of the helper devices.
>>
>> Reviewed-by: Mike Leach <mike.leach@linaro.org>
>> Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
>> ---
>>   drivers/hwtracing/coresight/coresight-core.c | 35 ++++++++++++++++++ 
>> ++++++++++
>>   drivers/hwtracing/coresight/coresight-priv.h |  2 ++
>>   2 files changed, 37 insertions(+)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/ 
>> hwtracing/coresight/coresight-core.c
>> index 0e8448784c62..667883ccb4b7 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -585,6 +585,41 @@ struct coresight_device 
>> *coresight_get_sink(struct coresight_path *path)
>>   }
>>   EXPORT_SYMBOL_GPL(coresight_get_sink);
>> +/**
>> + * coresight_get_helper: find the helper device of the assigned csdev.
>> + *
>> + * @csdev: The csdev the helper device is conntected to.
>> + * @type:  helper_subtype of the expected helper device.
>> + *
>> + * Retrieve the helper device for the specific csdev based on its
>> + * helper_subtype.
>> + *
>> + * Return: the helper's csdev upon success or NULL for fail.
>> + */
>> +struct coresight_device *coresight_get_helper(struct coresight_device 
>> *csdev,
>> +                          enum coresight_dev_subtype_helper subtype)
> 
> We have almost a similar function in coresight-core.c :
> 
> coresight_find_output_type(pdata, type, subtype).
> 
> Please could we reuse that, instead of adding similar funcitons ?
> 
> Please be careful about the mutex.
> 

Thanks for the suggestion. I reviewed coresight_find_output_type, and I 
believe we can reuse it to retrieve the CTCU device.

Thanks,
Jie

> Suzuki
> 
>> +{
>> +    int i;
>> +    struct coresight_device *helper;
>> +
>> +    /* protect the connections */
>> +    mutex_lock(&coresight_mutex);
>> +    for (i = 0; i < csdev->pdata->nr_outconns; ++i) {
>> +        helper = csdev->pdata->out_conns[i]->dest_dev;
>> +        if (!helper || !coresight_is_helper(helper))
>> +            continue;
>> +
>> +        if (helper->subtype.helper_subtype == subtype) {
>> +            mutex_unlock(&coresight_mutex);
>> +            return helper;
>> +        }
>> +    }
>> +    mutex_unlock(&coresight_mutex);
>> +
>> +    return NULL;
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_get_helper);
>> +
>>   /**
>>    * coresight_get_in_port: Find the input port number at @csdev where 
>> a @remote
>>    * device is connected to.
>> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/ 
>> hwtracing/coresight/coresight-priv.h
>> index cbf80b83e5ce..8e39a4dc7256 100644
>> --- a/drivers/hwtracing/coresight/coresight-priv.h
>> +++ b/drivers/hwtracing/coresight/coresight-priv.h
>> @@ -157,6 +157,8 @@ void coresight_path_assign_trace_id(struct 
>> coresight_path *path,
>>                      enum cs_mode mode);
>>   int coresight_get_in_port(struct coresight_device *csdev,
>>                 struct coresight_device *remote);
>> +struct coresight_device *coresight_get_helper(struct coresight_device 
>> *csdev,
>> +                          enum coresight_dev_subtype_helper subtype);
>>   #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
>>   int etm_readl_cp14(u32 off, unsigned int *val);
>>
>