Re: [PATCH v1 05/11] coresight: Save activated path into source device

[James Clark <james.clark@linaro.org>]

On 16/05/2025 5:07 pm, Leo Yan wrote:
> For a source device, save activated path into the coresight_device
> structure.
> 
> This will be used by sequential changes for controlling the path during
> CPU idle.
> 
> Signed-off-by: Leo Yan <leo.yan@arm.com>
> ---
>   drivers/hwtracing/coresight/coresight-core.c | 10 ++++++++++
>   include/linux/coresight.h                    |  3 +++
>   2 files changed, 13 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 7ab7321ca8d5..8f565bb3c535 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -495,6 +495,12 @@ static void coresight_disable_path_from(struct coresight_path *path,
>   
>   void coresight_disable_path(struct coresight_path *path)
>   {
> +	struct coresight_device *source;
> +
> +	source = coresight_get_source(path);
> +	if (coresight_is_percpu_source(source))
> +		source->path = NULL;
> +
>   	coresight_disable_path_from(path, NULL);
>   }
>   EXPORT_SYMBOL_GPL(coresight_disable_path);
> @@ -577,6 +583,10 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode,
>   		}
>   	}
>   
> +	source = coresight_get_source(path);
> +	if (coresight_is_percpu_source(source))
> +		source->path = path;
> +
>   out:
>   	return ret;
>   err_disable_helpers:
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index 64cee4040daa..cd9709a36b9c 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -265,6 +265,7 @@ struct coresight_trace_id_map {
>    *		CS_MODE_SYSFS. Otherwise it must be accessed from inside the
>    *		spinlock.
>    * @orphan:	true if the component has connections that haven't been linked.
> + * @path:	activated path pointer (only used for source device).
>    * @sysfs_sink_activated: 'true' when a sink has been selected for use via sysfs
>    *		by writing a 1 to the 'enable_sink' file.  A sink can be
>    *		activated but not yet enabled.  Enabling for a _sink_ happens
> @@ -291,6 +292,8 @@ struct coresight_device {
>   	local_t	mode;
>   	int refcnt;
>   	bool orphan;
> +	/* activated path (for source only) */
> +	struct coresight_path *path;

This is probably cleaner if it's saved in the new global per-cpu you 
added in patch 2. It's even more specific than "for source only", it's 
actually only for per-cpu sources so it's not worth having it on every 
device.

>   	/* sink specific fields */
>   	bool sysfs_sink_activated;
>   	struct dev_ext_attribute *ea;