Message-ID: <5f0a3b47-4dd5-8afb-796e-ddde70bbbdbc@arm.com>
Date:   Thu, 16 Mar 2023 20:23:28 +0000
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Subject: Re: [PATCH v2 6/9] coresight: Store in-connections as well as
 out-connections
To:     James Clark <james.clark@arm.com>, coresight@lists.linaro.org
Cc:     Mathieu Poirier <mathieu.poirier@linaro.org>,
        Mike Leach <mike.leach@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20230310160610.742382-1-james.clark@arm.com>
 <20230310160610.742382-7-james.clark@arm.com>
From:   Suzuki K Poulose <suzuki.poulose@arm.com>
In-Reply-To: <20230310160610.742382-7-james.clark@arm.com>
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Precedence: bulk

On 10/03/2023 16:06, James Clark wrote:
> This will allow CATU to get its associated ETR in a generic way where
> currently the enable path has some hard coded searches which avoid
> the need to store input connections.
> 
> Signed-off-by: James Clark <james.clark@arm.com>
> ---
>   drivers/hwtracing/coresight/coresight-core.c  | 56 +++++++++++++++--
>   .../hwtracing/coresight/coresight-platform.c  | 61 ++++++++++++++++---
>   drivers/hwtracing/coresight/coresight-sysfs.c |  1 -
>   include/linux/coresight.h                     | 25 ++++++++
>   4 files changed, 130 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index f457914e445e..a8ba7493c09a 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -59,6 +59,7 @@ const u32 coresight_barrier_pkt[4] = {0x7fffffff, 0x7fffffff, 0x7fffffff, 0x7fff
>   EXPORT_SYMBOL_GPL(coresight_barrier_pkt);
>   
>   static const struct cti_assoc_op *cti_assoc_ops;
> +static int coresight_fixup_inputs(struct coresight_device *csdev);
>   
>   ssize_t coresight_simple_show_pair(struct device *_dev,
>   			      struct device_attribute *attr, char *buf)
> @@ -1369,6 +1370,35 @@ static int coresight_fixup_orphan_conns(struct coresight_device *csdev)
>   			 csdev, coresight_orphan_match);
>   }
>   
> +/*
> + * Device connections are discovered before one/both devices have been created,
> + * so inputs must be added later.
> + */
> +static int coresight_fixup_inputs(struct coresight_device *csdev)
> +{
> +	int i, ret = 0;
> +	struct coresight_connection *out_conn;
> +	struct coresight_connection in_conn;
> +
> +	for (i = 0; i < csdev->pdata->nr_outconns; i++) {
> +		out_conn = &csdev->pdata->out_conns[i];
> +		if (!out_conn->remote_dev || !out_conn->remote_dev->pdata)
> +			continue;
> +
> +		/* Reverse local/remote relationships for inputs */
> +		in_conn.remote_dev = csdev;
> +		in_conn.remote_port = out_conn->port;
> +		in_conn.port = out_conn->remote_port;
> +		in_conn.remote_fwnode = csdev->dev.fwnode;
> +		ret = coresight_add_in_conn(out_conn->remote_dev->dev.parent,
> +					    out_conn->remote_dev->pdata,
> +					    &in_conn);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
>   
>   static int coresight_fixup_device_conns(struct coresight_device *csdev)
>   {
> @@ -1427,11 +1457,20 @@ static int coresight_remove_match(struct device *dev, void *data)

Removing the connection should be much simpler now with the inports
connection tracking.

i.e., coresight_remove_conns() need not iterate over all the devices on
the coresight bus. We had to do that to find all the devices connecting
to the removed device.

Instead with the in_conns we could readily get the csdev instance and
remove the connection from those devices.

Similarly for the out_conns can give you the remove device for removing
the in_conns on that device.

i.e,

static void coresight_remove_conns(csdev)
{
	struct coresight_device *remote;
	
	for (i = 0; i < csdev->pdata->nr_outconns; i++) {
		remote = csdev->data->out_conns[i].remote_dev;

		if (!remote)
			continue;

		for (j = 0; j < remote->pdata->nr_inconns; j++) {
			if (remote->pdata->in_conns[i].remote_dev ==  csdev)
			/* Clear in_conns[i] on remote */
		
		}
         }

	Similarly for in_conns
	for (i = 0; i < csdev->pdata->nr_inconns; i++) {
		remote = csdev->data->in_conns[i].remote_dev;

		if (!remote)
			continue;

		for (j = 0; j < remote->pdata->nr_outconns; j++) {
			if (remote->pdata->out_conns[i].remote_dev ==  csdev)
			/* Clear out_conns[i] on remote */
}


>   			 */
>   			fwnode_handle_put(conn->remote_fwnode);
>   			conn->remote_fwnode = NULL;
> +			conn->remote_dev = NULL;
> +			/* No need to continue */
> +			break;
> +		}
> +	}
> +	for (i = 0; i < iterator->pdata->nr_inconns; i++) {
> +		conn = &iterator->pdata->in_conns[i];
> +		if (csdev == conn->remote_dev) {
> +			conn->remote_fwnode = NULL;
> +			conn->remote_dev = NULL;
>   			/* No need to continue */
>   			break;
>   		}
>   	}
> -
>   	/*
>   	 * Returning '0' ensures that all known component on the
>   	 * bus will be checked.
> @@ -1552,21 +1591,28 @@ void coresight_release_platform_data(struct coresight_device *csdev,
>   
>   	for (i = 0; i < pdata->nr_outconns; i++) {
>   		/* If we have made the links, remove them now */
> -		if (csdev && conns[i].remote_dev)
> +		if (csdev && conns[i].remote_dev) {
>   			coresight_remove_links(csdev, &conns[i]);
> +			conns[i].remote_dev = NULL;
> +		}
> +
>   		/*
>   		 * Drop the refcount and clear the handle as this device
>   		 * is going away
>   		 */
>   		if (conns[i].remote_fwnode) {
>   			fwnode_handle_put(conns[i].remote_fwnode);
> -			pdata->out_conns[i].remote_fwnode = NULL;
> +			conns[i].remote_fwnode = NULL;
>   		}
>   	}
> +	for (i = 0; i < pdata->nr_inconns; i++) {
> +		pdata->in_conns[i].remote_dev = NULL;
> +		pdata->in_conns[i].remote_fwnode = NULL;
> +	}
> +
>   	if (csdev)
>   		coresight_remove_conns_sysfs_group(csdev);
>   }
> -
>   struct coresight_device *coresight_register(struct coresight_desc *desc)
>   {
>   	int ret;
> @@ -1659,6 +1705,8 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>   	ret = coresight_create_conns_sysfs_group(csdev);
>   	if (!ret)
>   		ret = coresight_fixup_device_conns(csdev);
> +	if (!ret)
> +		ret = coresight_fixup_inputs(csdev);
Don't we also need to fixup the "input" connections on this
device ? It would be good move all of this connection stuff
into a wrapper function.

>   	if (!ret)
>   		ret = coresight_fixup_orphan_conns(csdev);
>   
> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
> index 16553f7dde12..20e3351cbdc2 100644
> --- a/drivers/hwtracing/coresight/coresight-platform.c
> +++ b/drivers/hwtracing/coresight/coresight-platform.c
> @@ -20,8 +20,7 @@
>   
>   #include "coresight-priv.h"
>   /*
> - * coresight_alloc_conns: Allocate connections record for each output
> - * port from the device.
> + * coresight_alloc_conns: Allocate connections record for each input/output device.
>    */
>   static int coresight_alloc_conns(struct device *dev,
>   				 struct coresight_platform_data *pdata)
> @@ -33,7 +32,14 @@ static int coresight_alloc_conns(struct device *dev,
>   		if (!pdata->out_conns)
>   			return -ENOMEM;
>   	}
> -
> +	if (pdata->nr_inconns) {
> +		pdata->in_conns = devm_krealloc_array(dev, pdata->in_conns,
> +						      pdata->nr_inconns,
> +						      sizeof(*pdata->in_conns),
> +						      GFP_KERNEL | __GFP_ZERO);
> +		if (!pdata->in_conns)
> +			return -ENOMEM;
> +	}

devm_krealloc_array() skips any allocation if the requested new_size <=
origin_size. So this should be fine for the out_conns, to not realloc
the space again unnecessarily.

>   	return 0;
>   }
>   
> @@ -79,6 +85,45 @@ int coresight_add_conn(struct device *dev,
>   }
>   EXPORT_SYMBOL_GPL(coresight_add_conn);

Should this be named as add_out_conn in the previous patch
just to make it explicit and easier to read.

>   
> +/*
> + * Add a connection in the first free slot, or realloc
> + * if there is no space.
> + *
> + * Do nothing if the connection already exists because inputs are
> + * fixed up multiple times.
> + */
> +int coresight_add_in_conn(struct device *dev,
> +			  struct coresight_platform_data *pdata,

minor nit: Is there any reason why this can't simply be:

    int coresight_add_in_conn(struct coresight_device *csdev,
			     struct coresight_connection *conn)
    {
		struct device *dev = csdev->dev.parent;
		struct coresight_platform_data *pdata = csdev->pdata;

> +			  struct coresight_connection *conn)


Suzuki


> +{
> +	int ret;
> +	struct coresight_connection *free_conn = NULL;
> +	int i;
> +
> +	/* Search for a free slot or exit if a duplicate is found */
> +	if (pdata->in_conns) {
> +		for (i = 0; i < pdata->nr_inconns; ++i) {
> +			if (!free_conn && !pdata->in_conns[i].remote_fwnode)
> +				free_conn = &pdata->in_conns[i];
> +			if (pdata->in_conns[i].remote_fwnode ==
> +			    conn->remote_fwnode)
> +				return 0;
> +		}
> +	}
> +
> +	if (!free_conn) {
> +		pdata->nr_inconns++;
> +		ret = coresight_alloc_conns(dev, pdata);
> +		if (ret)
> +			return ret;
> +		free_conn = &pdata->in_conns[pdata->nr_inconns - 1];
> +	}
> +
> +	*free_conn = *conn;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(coresight_add_in_conn);
> +
>   static struct device *
>   coresight_find_device_by_fwnode(struct fwnode_handle *fwnode)
>   {
> @@ -249,7 +294,7 @@ static int of_coresight_get_cpu(struct device *dev)
>   
>   /*
>    * of_coresight_parse_endpoint : Parse the given output endpoint @ep
> - * and fill the connection information in @conn
> + * and fill the connection information in @in_conn and @out_conn
>    *
>    * Parses the local port, remote device name and the remote port.
>    *
> @@ -333,14 +378,14 @@ static int of_get_coresight_platform_data(struct device *dev,
>   	/* Get the number of input and output port for this component */
>   	of_coresight_get_ports(node, &pdata->nr_inconns, &pdata->nr_outconns);
>   
> -	/* If there are no output connections, we are done */
> -	if (!pdata->nr_outconns)
> -		return 0;
> -
>   	ret = coresight_alloc_conns(dev, pdata);
>   	if (ret)
>   		return ret;
>   
> +	/* If there are no output connections, we are done */
> +	if (!pdata->nr_outconns)
> +		return 0;
> +
>   	parent = of_coresight_get_output_ports_node(node);
>   	/*
>   	 * If the DT uses obsoleted bindings, the ports are listed
> diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c
> index 3da9868d9237..2abf9639ac0f 100644
> --- a/drivers/hwtracing/coresight/coresight-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-sysfs.c
> @@ -202,5 +202,4 @@ void coresight_remove_links(struct coresight_device *orig,
>   	devm_kfree(&orig->dev, conn->link->orig_name);
>   	devm_kfree(&orig->dev, conn->link);
>   	conn->link = NULL;
> -	conn->remote_dev = NULL;
>   }
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index 47fa58d6981d..fd268b24c761 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -110,6 +110,7 @@ struct coresight_platform_data {
>   	int nr_inconns;
>   	int nr_outconns;
>   	struct coresight_connection *out_conns;
> +	struct coresight_connection *in_conns;

Please document the field above the structure.

Suzuki


>   };
>   
>   /**
> @@ -177,6 +178,27 @@ struct coresight_desc {
>    *               @remote_fwnode once the remote's coresight_device has
>    *               been created.
>    * @link: Representation of the connection as a sysfs link.
> + *
> + * The full connection structure looks like this, where in_conns store references to
> + * the parent device in the same remote_dev member as output connections.
> + *
> + *       +-----------------------------+            +-----------------------------+
> + *       |coresight_device             |            |coresight_connection         |
> + *       |-----------------------------|            |-----------------------------|
> + *  ---->|                             |            |                             |
> + *  |    |                             |            |                  remote_dev*|------
> + *  |    |pdata->out_conns[nr_outconns]|----------->|                             |      |
> + *  |    |                             |            |                             |      |
> + *  |    +-----------------------------+            +-----------------------------+      |
> + *  |                                                                                    |
> + *  |    +-----------------------------+            +-----------------------------+      |
> + *  |    |coresight_connection         |            |coresight_device             |      |
> + *  |    |-----------------------------|            |------------------------------      |
> + *  |    |                             |            |                             |<-----
> + *  -----|remote_dev*                  |            |                             |
> + *       |                             |<-----------|pdata->in_conns[nr_inconns]  |
> + *       |                             |            |                             |
> + *       +-----------------------------+            +-----------------------------+
>    */
>   struct coresight_connection {
>   	int port;
> @@ -619,5 +641,8 @@ struct coresight_platform_data *coresight_get_platform_data(struct device *dev);
>   int coresight_add_conn(struct device *dev,
>   		       struct coresight_platform_data *pdata,
>   		       const struct coresight_connection *conn);
> +int coresight_add_in_conn(struct device *dev,
> +			  struct coresight_platform_data *pdata,
> +			  struct coresight_connection *conn);
>   
>   #endif		/* _LINUX_COREISGHT_H */