Hi Mathieu,

On Fri, 14 Feb 2020 at 23:17, Mathieu Poirier
[off-list ref] wrote:

On Tue, Feb 11, 2020 at 10:58:05AM +0000, Mike Leach wrote:

quoted

To allow the connections between coresight components to be represented
in sysfs, generic methods for creating sysfs links between two coresight
devices are added.

Signed-off-by: Mike Leach <redacted>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/Makefile          |   3 +-
 drivers/hwtracing/coresight/coresight-priv.h  |   4 +
 drivers/hwtracing/coresight/coresight-sysfs.c | 124 ++++++++++++++++++
 include/linux/coresight.h                     |  20 +++
 4 files changed, 150 insertions(+), 1 deletion(-)
 create mode 100644 drivers/hwtracing/coresight/coresight-sysfs.c

diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
index 0e3e72f0f510..19497d1d92bf 100644
--- a/drivers/hwtracing/coresight/Makefile
+++ b/drivers/hwtracing/coresight/Makefile

@@ -2,7 +2,8 @@
 #
 # Makefile for CoreSight drivers.
 #
-obj-$(CONFIG_CORESIGHT) += coresight.o coresight-etm-perf.o coresight-platform.o
+obj-$(CONFIG_CORESIGHT) += coresight.o coresight-etm-perf.o \
+                        coresight-platform.o coresight-sysfs.o
 obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o \
                                           coresight-tmc-etf.o \
                                           coresight-tmc-etr.o

diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index 1cad642f27aa..a4a658d46045 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h

@@ -153,6 +153,10 @@ struct coresight_device *coresight_get_sink_by_id(u32 id);
 struct list_head *coresight_build_path(struct coresight_device *csdev,
                                     struct coresight_device *sink);
 void coresight_release_path(struct list_head *path);
+int coresight_add_sysfs_link(struct coresight_sysfs_link *info);
+void coresight_remove_sysfs_link(struct coresight_sysfs_link *info);
+int coresight_create_conns_sysfs_group(struct coresight_device *csdev);
+void coresight_remove_conns_sysfs_group(struct coresight_device *csdev);

 #ifdef CONFIG_CORESIGHT_SOURCE_ETM3X
 extern int etm_readl_cp14(u32 off, unsigned int *val);

diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c
new file mode 100644
index 000000000000..17d565941e5e
--- /dev/null
+++ b/drivers/hwtracing/coresight/coresight-sysfs.c

@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019, Linaro Limited, All rights reserved.
+ * Author: Mike Leach <mike.leach@linaro.org>
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+
+#include "coresight-priv.h"
+
+/*
+ * Connections group - links attribute.
+ * Count of created links between coresight components in the group.
+ */
+static ssize_t nr_links_show(struct device *dev,
+                          struct device_attribute *attr,
+                          char *buf)
+{
+     struct coresight_device *csdev = to_coresight_device(dev);
+
+     return scnprintf(buf, PAGE_SIZE, "%d\n", csdev->nr_links);
+}
+static DEVICE_ATTR_RO(nr_links);
+
+static struct attribute *coresight_conns_attrs[] = {
+     &dev_attr_nr_links.attr,
+     NULL,
+};
+
+static struct attribute_group coresight_conns_group = {
+     .attrs = coresight_conns_attrs,
+     .name = "connections",
+};
+
+/*
+ * Create connections group for CoreSight devices.
+ * This group will then be used to collate the sysfs links between
+ * devices.
+ */
+int coresight_create_conns_sysfs_group(struct coresight_device *csdev)
+{
+     int ret = 0;
+
+     if (!csdev)
+             return -EINVAL;
+
+     ret = sysfs_create_group(&csdev->dev.kobj, &coresight_conns_group);
+     if (ret)
+             return ret;
+
+     csdev->has_conns_grp = true;

The only place coresight_create_conns_sysfs_group() is used is in
coresight_register() where an error is returned to driver probe() functions if
an error occurs.  Have you found places where csdev->has_conns_grp is needed?
If not please remove.

There is a sequence of calls in coresight_register() which occur after
the coresight_create_conns_sysfs_group() -
any one of which may throw an error resulting in an immediate
coresight_unregister() and hence
coresight_release_platform_data() => coresight_remove_conns_sysfs_group().
There is also an alternate path through coresight_register() which
also results in coresight_release_platform_data() occurring before we
have created the group.
The flag ensures that both paths clean up the sysfs connection data
correctly and safely.

Regards

Mike

quoted

+     return ret;
+}
+
+void coresight_remove_conns_sysfs_group(struct coresight_device *csdev)
+{
+     if (!csdev)
+             return;
+
+     if (csdev->has_conns_grp) {
+             sysfs_remove_group(&csdev->dev.kobj, &coresight_conns_group);
+             csdev->has_conns_grp = false;
+     }
+}
+
+int coresight_add_sysfs_link(struct coresight_sysfs_link *info)
+{
+     int ret = 0;
+
+     if (!info)
+             return -EINVAL;
+     if (!info->orig || !info->target ||
+         !info->orig_name || !info->target_name)
+             return -EINVAL;
+     if (!info->orig->has_conns_grp || !info->target->has_conns_grp)
+             return -EINVAL;
+
+     /* first link orig->target */
+     ret = sysfs_add_link_to_group(&info->orig->dev.kobj,
+                                   coresight_conns_group.name,
+                                   &info->target->dev.kobj,
+                                   info->orig_name);
+     if (ret)
+             return ret;
+
+     /* second link target->orig */
+     ret = sysfs_add_link_to_group(&info->target->dev.kobj,
+                                   coresight_conns_group.name,
+                                   &info->orig->dev.kobj,
+                                   info->target_name);
+
+     /* error in second link - remove first - otherwise inc counts */
+     if (ret) {
+             sysfs_remove_link_from_group(&info->orig->dev.kobj,
+                                          coresight_conns_group.name,
+                                          info->orig_name);
+     } else {
+             info->orig->nr_links++;
+             info->target->nr_links++;
+     }
+
+     return ret;
+}
+
+void coresight_remove_sysfs_link(struct coresight_sysfs_link *info)
+{
+     if (!info)
+             return;
+     if (!info->orig || !info->target ||
+         !info->orig_name || !info->target_name)
+             return;
+
+     sysfs_remove_link_from_group(&info->orig->dev.kobj,
+                                  coresight_conns_group.name,
+                                  info->orig_name);
+
+     sysfs_remove_link_from_group(&info->target->dev.kobj,
+                                  coresight_conns_group.name,
+                                  info->target_name);
+
+     info->orig->nr_links--;
+     info->target->nr_links--;
+}

diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 193cc9dbf448..a2ec25e02ca9 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h

@@ -148,6 +148,20 @@ struct coresight_connection {
      struct coresight_device *child_dev;
 };

+/**
+ * struct coresight_sysfs_link - representation of a connection in sysfs.
+ * @orig:            Originating (master) coresight device for the link.
+ * @orig_name:               Name to use for the link orig->target.
+ * @target:          Target (slave) coresight device for the link.
+ * @target_name:     Name to use for the link target->orig.
+ */
+struct coresight_sysfs_link {
+     struct coresight_device *orig;
+     const char *orig_name;
+     struct coresight_device *target;
+     const char *target_name;
+};
+
 /**
  * struct coresight_device - representation of a device as used by the framework
  * @pdata:   Platform data with device connections associated to this device.

@@ -165,6 +179,9 @@ struct coresight_connection {
  * @ea:              Device attribute for sink representation under PMU directory.
  * @ect_dev: Associated cross trigger device. Not part of the trace data
  *           path or connections.
+ * @nr_links:   number of sysfs links created to other components from this
+ *           device. These will appear in the "connections" group.
+ * @has_conns_grp: Have added a "connections" group for sysfs links.
  */
 struct coresight_device {
      struct coresight_platform_data *pdata;

@@ -180,6 +197,9 @@ struct coresight_device {
      struct dev_ext_attribute *ea;
      /* cross trigger handling */
      struct coresight_device *ect_dev;
+     /* sysfs links between components */
+     int nr_links;
+     bool has_conns_grp;
 };

With the above:

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

quoted

 /*
--
2.17.1

-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK