linux-kernel - Re: [PATCH v6 2/9] coresight: core: add a new API to retrieve the helper device

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Message-ID: <d5f1dd06-1c53-4656-882b-dbf771e3a125@oss.qualcomm.com>
Date: Thu, 4 Dec 2025 10:47:15 +0800
From: Jie Gan <jie.gan@....qualcomm.com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
        Jie Gan <jie.gan@....qualcomm.com>, Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Tingwei Zhang <tingwei.zhang@....qualcomm.com>,
        Jinlong Mao <jinlong.mao@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v6 2/9] coresight: core: add a new API to retrieve the
 helper device



On 12/4/2025 12:15 AM, Suzuki K Poulose wrote:
> On 08/09/2025 03:01, 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@...aro.org>
>> Signed-off-by: Jie Gan <jie.gan@....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 042c4fa39e55..018b1119c48a 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -580,6 +580,41 @@ 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,
> 
>> +                          int type)
> 
> nit: enum coresight_dev_subtype_helper subtype
> 
> Otherwise looks good to me

Will update in next version.

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 == type) {
>> +            mutex_unlock(&coresight_mutex);
>> +            return helper;
>> +        }
>> +    }
>> +    mutex_unlock(&coresight_mutex);
>> +
>> +    return NULL;
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_get_helper);
>> +
>>   /**
>>    * coresight_get_in_port_dest: get the in-port number of the dest 
>> device
>>    * that is connected to the src device.
>> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/ 
>> hwtracing/coresight/coresight-priv.h
>> index e51b22b8ebde..f80122827934 100644
>> --- a/drivers/hwtracing/coresight/coresight-priv.h
>> +++ b/drivers/hwtracing/coresight/coresight-priv.h
>> @@ -158,6 +158,8 @@ void coresight_path_assign_trace_id(struct 
>> coresight_path *path,
>>                      enum cs_mode mode);
>>   int coresight_get_in_port_dest(struct coresight_device *src,
>>                      struct coresight_device *dest);
>> +struct coresight_device *coresight_get_helper(struct coresight_device 
>> *csdev,
>> +                          int type);
>>   #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
>>   int etm_readl_cp14(u32 off, unsigned int *val);
>>
> 
>