linux-kernel - Re: [PATCH v4 02/10] coresight: core: add a new API to retrieve the helper device

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Message-ID: <CAJ9a7ViT2BAw6t65A3bbyzQd3Tr6qT_yTa5EGwhKarEipaO=Cw@mail.gmail.com>
Date: Tue, 5 Aug 2025 10:57:23 +0100
From: Mike Leach <mike.leach@...aro.org>
To: Jie Gan <jie.gan@....qualcomm.com>
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 <tingwei.zhang@....qualcomm.com>, Jinlong Mao <jinlong.mao@....qualcomm.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, Jie Gan <quic_jiegan@...cinc.com>
Subject: Re: [PATCH v4 02/10] coresight: core: add a new API to retrieve the
 helper device

On Fri, 25 Jul 2025 at 11:08, 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 | 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)
> +{
> +       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);
> --
> 2.34.1
>

Reviewed-by: Mike Leach <mike.leach@...aro.org>
-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK