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: <CAJ9a7VikU9UktC-fpLfR5EdpGupHHor2GaDGAujBnQJky=W17w@mail.gmail.com>
Date: Fri, 18 Jul 2025 09:37:46 +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 <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

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

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
>


-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK