linux-kernel - Re: [PATCH v3 RESEND 02/10] coresight: core: add a new API to retrieve the helper device

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Message-ID: <da49f445-7365-4863-bb41-f7a55150c4dd@oss.qualcomm.com>
Date: Fri, 18 Jul 2025 17:36:33 +0800
From: Jie Gan <jie.gan@....qualcomm.com>
To: Mike Leach <mike.leach@...aro.org>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
        James Clark <james.clark@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Mao Jinlong <quic_jinlmao@...cinc.com>,
        Jie Gan <quic_jiegan@...cinc.com>, 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 v3 RESEND 02/10] coresight: core: add a new API to
 retrieve the helper device



On 7/18/2025 4:37 PM, Mike Leach wrote:
> Hi,
> 
> On Mon, 14 Jul 2025 at 07:31, Jie Gan <jie.gan@....qualcomm.com> 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.
>>
>> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
>> ---
>>   drivers/hwtracing/coresight/coresight-core.c | 30 ++++++++++++++++++++
>>   drivers/hwtracing/coresight/coresight-priv.h |  2 ++
>>   2 files changed, 32 insertions(+)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
>> index 5297a5ff7921..76e10c36a8a1 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -580,6 +580,36 @@ 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)
>> +{
>> +       int i;
>> +       struct coresight_device *helper;
>> +
>> +       for (i = 0; i < csdev->pdata->nr_outconns; ++i) {
>> +               helper = csdev->pdata->out_conns[i]->dest_dev;
>> +               if (!helper || !coresight_is_helper(helper))
>> +                       continue;
>> +
> 
> Manipulating the connections list almost certainly requires some
> locking. See other functions in this file
> 

Thanks for pointing out. I will fix it in next version.

Thanks,
Jie

> Mike
> 
> 
>> +               if (helper->subtype.helper_subtype == type)
>> +                       return helper;
>> +       }
>> +
>> +       return NULL;
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_get_helper);
>> +
>>   /**
>>    * coresight_get_port_helper: get the in-port number of the helper device
>>    * that is connected to the csdev.
>> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
>> index 07a5f03de81d..5b912eb60401 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_port_helper(struct coresight_device *csdev,
>>                                struct coresight_device *helper);
>> +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);
>> --
>> 2.34.1
>>
> 
>