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

[Jie Gan]

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@xxxxxxxxxx>
> > Signed-off-by: Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>
> > ---
> >   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);