Message-ID: <137f3f74-0732-4a01-9c14-680ab45107d8@arm.com>
Date: Mon, 8 Jan 2024 11:21:09 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: James Clark <james.clark@....com>, coresight@...ts.linaro.org
Cc: Mike Leach <mike.leach@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH 2/8] coresight: Make language around "activated" sinks
 consistent

Hi James,


On 12/12/2023 15:53, James Clark wrote:
> Activated has the specific meaning of a sink that's selected for use by
> the user via sysfs. But comments in some code that's shared by Perf use
> the same word, so in those cases change them to just say "selected"
> instead. With selected implying either via Perf or "activated" via
> sysfs.
> 
> coresight_get_enabled_sink() doesn't actually get an enabled sink, it
> only gets an activated one, so change that too.
> 

These changes look good to me. Please see a minor nit below.

> And change the activated variable name to include "sysfs" so it can't
> be confused as a general status.
> 
> Signed-off-by: James Clark <james.clark@....com>
> ---
>   drivers/hwtracing/coresight/coresight-core.c | 51 ++++++++------------
>   drivers/hwtracing/coresight/coresight-priv.h |  2 -
>   include/linux/coresight.h                    | 14 +++---
>   3 files changed, 27 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 965bb6d4e1bf..f79aa9ff9b64 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -500,7 +500,7 @@ static void coresight_disable_path_from(struct list_head *path,
>   		/*
>   		 * ETF devices are tricky... They can be a link or a sink,
>   		 * depending on how they are configured.  If an ETF has been
> -		 * "activated" it will be configured as a sink, otherwise
> +		 * selected as a sink it will be configured as a sink, otherwise
>   		 * go ahead with the link configuration.
>   		 */
>   		if (type == CORESIGHT_DEV_TYPE_LINKSINK)
> @@ -578,7 +578,7 @@ int coresight_enable_path(struct list_head *path, enum cs_mode mode,
>   		/*
>   		 * ETF devices are tricky... They can be a link or a sink,
>   		 * depending on how they are configured.  If an ETF has been
> -		 * "activated" it will be configured as a sink, otherwise
> +		 * selected as a sink it will be configured as a sink, otherwise
>   		 * go ahead with the link configuration.
>   		 */
>   		if (type == CORESIGHT_DEV_TYPE_LINKSINK)
> @@ -635,15 +635,21 @@ struct coresight_device *coresight_get_sink(struct list_head *path)
>   	return csdev;
>   }
>   
> +/**
> + * coresight_find_activated_sysfs_sink - returns the first sink activated via
> + * sysfs using connection based search starting from the source reference.
> + *
> + * @csdev: Coresight source device reference
> + */
>   static struct coresight_device *
> -coresight_find_enabled_sink(struct coresight_device *csdev)
> +coresight_find_activated_sysfs_sink(struct coresight_device *csdev)
>   {
>   	int i;
>   	struct coresight_device *sink = NULL;
>   
>   	if ((csdev->type == CORESIGHT_DEV_TYPE_SINK ||
>   	     csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) &&
> -	     csdev->activated)
> +	     csdev->sysfs_sink_activated)
>   		return csdev;
>   
>   	/*
> @@ -654,7 +660,7 @@ coresight_find_enabled_sink(struct coresight_device *csdev)
>   
>   		child_dev = csdev->pdata->out_conns[i]->dest_dev;
>   		if (child_dev)
> -			sink = coresight_find_enabled_sink(child_dev);
> +			sink = coresight_find_activated_sysfs_sink(child_dev);
>   		if (sink)
>   			return sink;
>   	}
> @@ -662,21 +668,6 @@ coresight_find_enabled_sink(struct coresight_device *csdev)
>   	return NULL;
>   }
>   
> -/**
> - * coresight_get_enabled_sink - returns the first enabled sink using
> - * connection based search starting from the source reference
> - *
> - * @source: Coresight source device reference
> - */
> -struct coresight_device *
> -coresight_get_enabled_sink(struct coresight_device *source)
> -{
> -	if (!source)
> -		return NULL;
> -
> -	return coresight_find_enabled_sink(source);
> -}
> -
>   static int coresight_sink_by_id(struct device *dev, const void *data)
>   {
>   	struct coresight_device *csdev = to_coresight_device(dev);
> @@ -810,11 +801,10 @@ static void coresight_drop_device(struct coresight_device *csdev)
>    * @sink:	The final sink we want in this path.
>    * @path:	The list to add devices to.
>    *
> - * The tree of Coresight device is traversed until an activated sink is
> - * found.  From there the sink is added to the list along with all the
> - * devices that led to that point - the end result is a list from source
> - * to sink. In that list the source is the first device and the sink the
> - * last one.
> + * The tree of Coresight device is traversed until the selected sink is found.

minor nit: s/until the selected/until *a* selected/

There could be multiple sinks activated that can be reached from the 
source. But we choose the "closest" possible selected sink for a source.
So, it may be better to drop "the".


> + * From there the sink is added to the list along with all the devices that led
> + * to that point - the end result is a list from source to sink. In that list
> + * the source is the first device and the sink the last one.
>    */
>   static int _coresight_build_path(struct coresight_device *csdev,
>   				 struct coresight_device *sink,
> @@ -824,7 +814,7 @@ static int _coresight_build_path(struct coresight_device *csdev,
>   	bool found = false;
>   	struct coresight_node *node;
>   
> -	/* An activated sink has been found.  Enqueue the element */
> +	/* The selected sink has been found.  Enqueue the element */

Similarly here.

Rest looks fine to me.

Suzuki


>   	if (csdev == sink)
>   		goto out;
>   
> @@ -1145,7 +1135,7 @@ int coresight_enable(struct coresight_device *csdev)
>   		goto out;
>   	}
>   
> -	sink = coresight_get_enabled_sink(csdev);
> +	sink = coresight_find_activated_sysfs_sink(csdev);
>   	if (!sink) {
>   		ret = -EINVAL;
>   		goto out;
> @@ -1259,7 +1249,7 @@ static ssize_t enable_sink_show(struct device *dev,
>   {
>   	struct coresight_device *csdev = to_coresight_device(dev);
>   
> -	return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->activated);
> +	return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->sysfs_sink_activated);
>   }
>   
>   static ssize_t enable_sink_store(struct device *dev,
> @@ -1274,10 +1264,7 @@ static ssize_t enable_sink_store(struct device *dev,
>   	if (ret)
>   		return ret;
>   
> -	if (val)
> -		csdev->activated = true;
> -	else
> -		csdev->activated = false;
> +	csdev->sysfs_sink_activated = !!val;
>   
>   	return size;
>   
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index 30c051055e54..ced5be05a527 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -130,8 +130,6 @@ void coresight_disable_path(struct list_head *path);
>   int coresight_enable_path(struct list_head *path, enum cs_mode mode,
>   			  void *sink_data);
>   struct coresight_device *coresight_get_sink(struct list_head *path);
> -struct coresight_device *
> -coresight_get_enabled_sink(struct coresight_device *source);
>   struct coresight_device *coresight_get_sink_by_id(u32 id);
>   struct coresight_device *
>   coresight_find_default_sink(struct coresight_device *csdev);
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index a4cb7dd6ca23..65131bfbd904 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -229,10 +229,12 @@ struct coresight_sysfs_link {
>    * @refcnt:	keep track of what is in use.
>    * @orphan:	true if the component has connections that haven't been linked.
>    * @enable:	'true' if component is currently part of an active path.
> - * @activated:	'true' only if a _sink_ has been activated.  A sink can be
> - *		activated but not yet enabled.  Enabling for a _sink_
> - *		happens when a source has been selected and a path is enabled
> - *		from source to that sink.
> + * @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
> + *		when a source has been selected and a path is enabled from
> + *		source to that sink. A sink can also become enabled but not
> + *		activated if it's used via Perf.
>    * @ea:		Device attribute for sink representation under PMU directory.
>    * @def_sink:	cached reference to default sink found for this device.
>    * @nr_links:   number of sysfs links created to other components from this
> @@ -252,9 +254,9 @@ struct coresight_device {
>   	struct device dev;
>   	atomic_t refcnt;
>   	bool orphan;
> -	bool enable;	/* true only if configured as part of a path */
> +	bool enable;
>   	/* sink specific fields */
> -	bool activated;	/* true only if a sink is part of a path */
> +	bool sysfs_sink_activated;
>   	struct dev_ext_attribute *ea;
>   	struct coresight_device *def_sink;
>   	/* sysfs links between components */

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