Re: [PATCH v2 36/36] [RFC] coresight: Expose device connections via sysfs

From: Mathieu Poirier
Date: Mon Apr 29 2019 - 16:50:15 EST

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On Mon, Apr 15, 2019 at 05:04:19PM +0100, Suzuki K Poulose wrote:
> Coresight device connections are a bit complicated and is not
> exposed currently to the user. One has to look at the platform
> descriptions (DT bindings or ACPI bindings) to make an understanding.
> Given the new naming scheme, it will be helpful to have this information
> to choose the appropriate devices for tracing. This patch exposes
> the device connections via links in the sysfs directories.
>
> e.g, for a connection devA[OutputPort_X] -> devB[InputPort_Y]
> is represented as two symlinks:
>
> /sys/bus/coresight/.../devA/out:X -> /sys/bus/coresight/.../devB
> /sys/bus/coresight/.../devB/in:Y -> /sys/bus/coresight/.../devA
>
> We could have segregated the links to separate directories aka
> attribute_groups, for input_ports and output_ports. But the sysfs won't
> let you create empty attribute_groups and thus it becomes complicated to
> dynamically create the attribute_groups.

While testing this set I noticed entries in /sys/bus/event_source/sinks still
advertise platform device names. To fix this etm_perf_add_symlink_sink()
needs to be modified, more specifically:

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 4d5a2b9f9d6a..b6d8b8c2ceb9 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -507,7 +507,7 @@ int etm_perf_add_symlink_sink(struct coresight_device *csdev)
unsigned long hash;
const char *name;
struct device *pmu_dev = etm_pmu.dev;
- struct device *pdev = csdev->dev.parent;
+ struct device *dev = &csdev->dev;
struct dev_ext_attribute *ea;

if (csdev->type != CORESIGHT_DEV_TYPE_SINK &&
@@ -520,15 +520,15 @@ int etm_perf_add_symlink_sink(struct coresight_device *csdev)
if (!etm_perf_up)
return -EPROBE_DEFER;

- ea = devm_kzalloc(pdev, sizeof(*ea), GFP_KERNEL);
+ ea = devm_kzalloc(dev, sizeof(*ea), GFP_KERNEL);
if (!ea)
return -ENOMEM;

- name = dev_name(pdev);
+ name = dev_name(dev);
/* See function coresight_get_sink_by_id() to know where this is used */
hash = hashlen_hash(hashlen_string(NULL, name));

- ea->attr.attr.name = devm_kstrdup(pdev, name, GFP_KERNEL);
+ ea->attr.attr.name = devm_kstrdup(dev, name, GFP_KERNEL);
if (!ea->attr.attr.name)
return -ENOMEM;

Mike Leach was also working on a way to represent connections between CTI/CTM
devices. It would be desirable to get the same kind of topology representation
for both "normal" devices and CTI/CTMs. I like how this set represent the
topology but I also want Mike to have his say as well.

Before moving forward I will need to get a "Reviewed-by" from him.

Thanks,
Mathieu

>
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> drivers/hwtracing/coresight/coresight.c | 120 +++++++++++++++++++++++++++++---
> include/linux/coresight.h | 4 ++
> 2 files changed, 113 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
> index 4d63063..50a1f29 100644
> --- a/drivers/hwtracing/coresight/coresight.c
> +++ b/drivers/hwtracing/coresight/coresight.c
> @@ -981,9 +981,92 @@ static void coresight_device_release(struct device *dev)
> kfree(csdev);
> }
>
> +
> +/*
> + * coresight_make_links: Make a link for a connection from a @orig
> + * device to @target, represented by @conn.
> + *
> + * e.g, for devOrig[output_X] -> devTarget[input_Y] is represented
> + * as two symbolic links :
> + *
> + * /sys/.../devOrig/out:X -> /sys/.../devTarget/
> + * /sys/.../devTarget/in:Y -> /sys/.../devOrig/
> + *
> + * The link names are allocated for a device where it appears. i.e, the
> + * "out" link on the master and "in" link on the slave device.
> + * The link names are stored in the connection record for avoiding
> + * the reconstruction of names for removal.
> + */
> +static int coresight_make_links(struct coresight_device *orig,
> + struct coresight_connection *conn,
> + struct coresight_device *target)
> +{
> + int ret = -ENOMEM;
> + char *outs = NULL, *ins = NULL;
> +
> + do {
> + outs = devm_kasprintf(&orig->dev, GFP_KERNEL,
> + "out:%d", conn->outport);
> + if (!outs)
> + break;
> + ins = devm_kasprintf(&target->dev, GFP_KERNEL,
> + "in:%d", conn->child_port);
> + if (!ins)
> + break;
> + ret = sysfs_create_link(&orig->dev.kobj,
> + &target->dev.kobj, outs);
> + if (ret)
> + break;
> +
> + ret = sysfs_create_link(&target->dev.kobj,
> + &orig->dev.kobj, ins);
> + if (ret) {
> + sysfs_remove_link(&orig->dev.kobj, outs);
> + break;
> + }
> +
> + conn->inlink_name = ins;
> + conn->outlink_name = outs;
> + /*
> + * Install the device connection. This also indicates that
> + * the links are operational on both ends.
> + */
> + conn->child_dev = target;
> + return 0;
> + } while (0);
> +
> + if (outs)
> + devm_kfree(&orig->dev, outs);
> + if (ins)
> + devm_kfree(&target->dev, ins);
> + return ret;
> +}
> +
> +/*
> + * coresight_remove_links: Remove the sysfs links for a given connection @conn,
> + * from @orig device to @target device. See coresight_make_links() for more
> + * details.
> + */
> +static void coresight_remove_links(struct coresight_device *orig,
> + struct coresight_connection *conn)
> +{
> + struct coresight_device *target = conn->child_dev;
> +
> + if (!orig || !target)
> + return;
> +
> + sysfs_remove_link(&orig->dev.kobj, conn->outlink_name);
> + sysfs_remove_link(&target->dev.kobj, conn->inlink_name);
> +
> + devm_kfree(&target->dev, conn->inlink_name);
> + devm_kfree(&orig->dev, conn->outlink_name);
> + conn->inlink_name = conn->outlink_name = NULL;
> + conn->child_dev = NULL;
> +}
> +
> static int coresight_orphan_match(struct device *dev, void *data)
> {
> - int i;
> + int i, ret = 0;
> bool still_orphan = false;
> struct coresight_device *csdev, *i_csdev;
> struct coresight_connection *conn;
> @@ -1008,19 +1091,23 @@ static int coresight_orphan_match(struct device *dev, void *data)
> /* We have found at least one orphan connection */
> if (conn->child_dev == NULL) {
> /* Does it match this newly added device? */
> - if (conn->child_fwnode == csdev->dev.fwnode)
> - conn->child_dev = csdev;
> - else
> + if (conn->child_fwnode == csdev->dev.fwnode) {
> + ret = coresight_make_links(i_csdev,
> + conn, csdev);
> + if (ret)
> + return ret;
> + } else {
> /* This component still has an orphan */
> still_orphan = true;
> + }
> }
> }
>
> i_csdev->orphan = still_orphan;
>
> /*
> - * Returning '0' ensures that all known component on the
> - * bus will be checked.
> + * Returning '0' in case we didn't encounter any error,
> + * ensures that all known component on the bus will be checked.
> */
> return 0;
> }
> @@ -1038,7 +1125,7 @@ static int coresight_fixup_orphan_conns(struct coresight_device *csdev)
>
> static int coresight_fixup_device_conns(struct coresight_device *csdev)
> {
> - int i;
> + int i, ret = 0;
>
> for (i = 0; i < csdev->pdata->nr_outport; i++) {
> struct coresight_connection *conn = &csdev->pdata->conns[i];
> @@ -1048,9 +1135,12 @@ static int coresight_fixup_device_conns(struct coresight_device *csdev)
> (void *)conn->child_fwnode,
> device_fwnode_match);
> if (dev) {
> - conn->child_dev = to_coresight_device(dev);
> + ret = coresight_make_links(csdev, conn,
> + to_coresight_device(dev));
> /* and put reference from 'bus_find_device()' */
> put_device(dev);
> + if (ret)
> + break;
> } else {
> csdev->orphan = true;
> conn->child_dev = NULL;
> @@ -1085,7 +1175,7 @@ static int coresight_remove_match(struct device *dev, void *data)
>
> if (csdev->dev.fwnode == conn->child_fwnode) {
> iterator->orphan = true;
> - conn->child_dev = NULL;
> + coresight_remove_links(iterator, conn);
> /*
> * Drop the reference to the handle for the remote
> * device acquired in parsing the connections from
> @@ -1179,10 +1269,18 @@ void coresight_release_platform_data(struct coresight_device *csdev,
> struct coresight_platform_data *pdata)
> {
> int i;
> + struct coresight_connection *conns = pdata->conns;
>
> for (i = 0; i < pdata->nr_outport; i++) {
> - if (pdata->conns[i].child_fwnode) {
> - fwnode_handle_put(pdata->conns[i].child_fwnode);
> + /* If we have made the links, remove them now */
> + if (csdev && conns[i].child_dev)
> + coresight_remove_links(csdev, &conns[i]);
> + /*
> + * Drop the refcount and clear the handle as this device
> + * is going away
> + */
> + if (conns[i].child_fwnode) {
> + fwnode_handle_put(conns[i].child_fwnode);
> pdata->conns[i].child_fwnode = 0;
> }
> }
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index d6367a0..284d783 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -130,12 +130,16 @@ struct coresight_desc {
> * @chid_fwnode: remote component's fwnode handle.
> * @child_dev: a @coresight_device representation of the component
> connected to @outport.
> + * @inlink_name: Name for the "input" link
> + * @outlink_name: Name for the "output" link
> */
> struct coresight_connection {
> int outport;
> int child_port;
> struct fwnode_handle *child_fwnode;
> struct coresight_device *child_dev;
> + const char *inlink_name;
> + const char *outlink_name;
> };
>
> /**
> --
> 2.7.4
>

Next message: Christian Brauner: "Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add CLONE_PIDFD]"
Previous message: Florian Weimer: "Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add CLONE_PIDFD]"
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