stm class: Introduce an abstraction for System Trace Module devices

A System Trace Module (STM) is a device exporting data in System Trace
Protocol (STP) format as defined by MIPI STP standards. Examples of such
devices are Intel(R) Trace Hub and Coresight STM.

This abstraction provides a unified interface for software trace sources
to send their data over an STM device to a debug host. In order to do
that, such a trace source needs to be assigned a pair of master/channel
identifiers that all the data from this source will be tagged with. The
STP decoder on the debug host side will use these master/channel tags to
distinguish different trace streams from one another inside one STP
stream.

This abstraction provides a configfs-based policy management mechanism
for dynamic allocation of these master/channel pairs based on trace
source-supplied string identifier. It has the flexibility of being
defined at runtime and at the same time (provided that the policy
definition is aligned with the decoding end) consistency.

For userspace trace sources, this abstraction provides write()-based and
mmap()-based (if the underlying stm device allows this) output mechanism.

For kernel-side trace sources, we provide "stm_source" device class that
can be connected to an stm device at run time.

Cc: linux-api@vger.kernel.org
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 529 insertions, 0 deletions

diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
new file mode 100644
index 000000000000..6498a9dbb7bd
--- /dev/null
+++ b/drivers/hwtracing/stm/policy.c
@@ -0,0 +1,529 @@
+/*
+ * System Trace Module (STM) master/channel allocation policy management
+ * Copyright (c) 2014, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * A master/channel allocation policy allows mapping string identifiers to
+ * master and channel ranges, where allocation can be done.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/configfs.h>
+#include <linux/slab.h>
+#include <linux/stm.h>
+#include "stm.h"
+
+/*
+ * STP Master/Channel allocation policy configfs layout.
+ */
+
+struct stp_policy {
+	struct config_group	group;
+	struct stm_device	*stm;
+};
+
+struct stp_policy_node {
+	struct config_group	group;
+	struct stp_policy	*policy;
+	unsigned int		first_master;
+	unsigned int		last_master;
+	unsigned int		first_channel;
+	unsigned int		last_channel;
+};
+
+static struct configfs_subsystem stp_policy_subsys;
+
+void stp_policy_node_get_ranges(struct stp_policy_node *policy_node,
+				unsigned int *mstart, unsigned int *mend,
+				unsigned int *cstart, unsigned int *cend)
+{
+	*mstart	= policy_node->first_master;
+	*mend	= policy_node->last_master;
+	*cstart	= policy_node->first_channel;
+	*cend	= policy_node->last_channel;
+}
+
+static inline char *stp_policy_node_name(struct stp_policy_node *policy_node)
+{
+	return policy_node->group.cg_item.ci_name ? : "<none>";
+}
+
+static inline struct stp_policy *to_stp_policy(struct config_item *item)
+{
+	return item ?
+		container_of(to_config_group(item), struct stp_policy, group) :
+		NULL;
+}
+
+static inline struct stp_policy_node *
+to_stp_policy_node(struct config_item *item)
+{
+	return item ?
+		container_of(to_config_group(item), struct stp_policy_node,
+			     group) :
+		NULL;
+}
+
+static ssize_t stp_policy_node_masters_show(struct stp_policy_node *policy_node,
+					    char *page)
+{
+	ssize_t count;
+
+	count = sprintf(page, "%u %u\n", policy_node->first_master,
+			policy_node->last_master);
+
+	return count;
+}
+
+static ssize_t
+stp_policy_node_masters_store(struct stp_policy_node *policy_node,
+			      const char *page, size_t count)
+{
+	unsigned int first, last;
+	struct stm_device *stm;
+	char *p = (char *)page;
+	ssize_t ret = -ENODEV;
+
+	if (sscanf(p, "%u %u", &first, &last) != 2)
+		return -EINVAL;
+
+	mutex_lock(&stp_policy_subsys.su_mutex);
+	stm = policy_node->policy->stm;
+	if (!stm)
+		goto unlock;
+
+	/* must be within [sw_start..sw_end], which is an inclusive range */
+	if (first > INT_MAX || last > INT_MAX || first > last ||
+	    first < stm->data->sw_start ||
+	    last > stm->data->sw_end) {
+		ret = -ERANGE;
+		goto unlock;
+	}
+
+	ret = count;
+	policy_node->first_master = first;
+	policy_node->last_master = last;
+
+unlock:
+	mutex_unlock(&stp_policy_subsys.su_mutex);
+
+	return ret;
+}
+
+static ssize_t
+stp_policy_node_channels_show(struct stp_policy_node *policy_node, char *page)
+{
+	ssize_t count;
+
+	count = sprintf(page, "%u %u\n", policy_node->first_channel,
+			policy_node->last_channel);
+
+	return count;
+}
+
+static ssize_t
+stp_policy_node_channels_store(struct stp_policy_node *policy_node,
+			       const char *page, size_t count)
+{
+	unsigned int first, last;
+	struct stm_device *stm;
+	char *p = (char *)page;
+	ssize_t ret = -ENODEV;
+
+	if (sscanf(p, "%u %u", &first, &last) != 2)
+		return -EINVAL;
+
+	mutex_lock(&stp_policy_subsys.su_mutex);
+	stm = policy_node->policy->stm;
+	if (!stm)
+		goto unlock;
+
+	if (first > INT_MAX || last > INT_MAX || first > last ||
+	    last >= stm->data->sw_nchannels) {
+		ret = -ERANGE;
+		goto unlock;
+	}
+
+	ret = count;
+	policy_node->first_channel = first;
+	policy_node->last_channel = last;
+
+unlock:
+	mutex_unlock(&stp_policy_subsys.su_mutex);
+
+	return ret;
+}
+
+static void stp_policy_node_release(struct config_item *item)
+{
+	kfree(to_stp_policy_node(item));
+}
+
+struct stp_policy_node_attribute {
+	struct configfs_attribute	attr;
+	ssize_t (*show)(struct stp_policy_node *, char *);
+	ssize_t (*store)(struct stp_policy_node *, const char *, size_t);
+};
+
+static ssize_t stp_policy_node_attr_show(struct config_item *item,
+					 struct configfs_attribute *attr,
+					 char *page)
+{
+	struct stp_policy_node *policy_node = to_stp_policy_node(item);
+	struct stp_policy_node_attribute *pn_attr =
+		container_of(attr, struct stp_policy_node_attribute, attr);
+	ssize_t count = 0;
+
+	if (pn_attr->show)
+		count = pn_attr->show(policy_node, page);
+
+	return count;
+}
+
+static ssize_t stp_policy_node_attr_store(struct config_item *item,
+					  struct configfs_attribute *attr,
+					  const char *page, size_t len)
+{
+	struct stp_policy_node *policy_node = to_stp_policy_node(item);
+	struct stp_policy_node_attribute *pn_attr =
+		container_of(attr, struct stp_policy_node_attribute, attr);
+	ssize_t count = -EINVAL;
+
+	if (pn_attr->store)
+		count = pn_attr->store(policy_node, page, len);
+
+	return count;
+}
+
+static struct configfs_item_operations stp_policy_node_item_ops = {
+	.release		= stp_policy_node_release,
+	.show_attribute		= stp_policy_node_attr_show,
+	.store_attribute	= stp_policy_node_attr_store,
+};
+
+static struct stp_policy_node_attribute stp_policy_node_attr_range = {
+	.attr	= {
+		.ca_owner = THIS_MODULE,
+		.ca_name = "masters",
+		.ca_mode = S_IRUGO | S_IWUSR,
+	},
+	.show	= stp_policy_node_masters_show,
+	.store	= stp_policy_node_masters_store,
+};
+
+static struct stp_policy_node_attribute stp_policy_node_attr_channels = {
+	.attr	= {
+		.ca_owner = THIS_MODULE,
+		.ca_name = "channels",
+		.ca_mode = S_IRUGO | S_IWUSR,
+	},
+	.show	= stp_policy_node_channels_show,
+	.store	= stp_policy_node_channels_store,
+};
+
+static struct configfs_attribute *stp_policy_node_attrs[] = {
+	&stp_policy_node_attr_range.attr,
+	&stp_policy_node_attr_channels.attr,
+	NULL,
+};
+
+static struct config_item_type stp_policy_type;
+static struct config_item_type stp_policy_node_type;
+
+static struct config_group *
+stp_policy_node_make(struct config_group *group, const char *name)
+{
+	struct stp_policy_node *policy_node, *parent_node;
+	struct stp_policy *policy;
+
+	if (group->cg_item.ci_type == &stp_policy_type) {
+		policy = container_of(group, struct stp_policy, group);
+	} else {
+		parent_node = container_of(group, struct stp_policy_node,
+					   group);
+		policy = parent_node->policy;
+	}
+
+	if (!policy->stm)
+		return ERR_PTR(-ENODEV);
+
+	policy_node = kzalloc(sizeof(struct stp_policy_node), GFP_KERNEL);
+	if (!policy_node)
+		return ERR_PTR(-ENOMEM);
+
+	config_group_init_type_name(&policy_node->group, name,
+				    &stp_policy_node_type);
+
+	policy_node->policy = policy;
+
+	/* default values for the attributes */
+	policy_node->first_master = policy->stm->data->sw_start;
+	policy_node->last_master = policy->stm->data->sw_end;
+	policy_node->first_channel = 0;
+	policy_node->last_channel = policy->stm->data->sw_nchannels - 1;
+
+	return &policy_node->group;
+}
+
+static void
+stp_policy_node_drop(struct config_group *group, struct config_item *item)
+{
+	config_item_put(item);
+}
+
+static struct configfs_group_operations stp_policy_node_group_ops = {
+	.make_group	= stp_policy_node_make,
+	.drop_item	= stp_policy_node_drop,
+};
+
+static struct config_item_type stp_policy_node_type = {
+	.ct_item_ops	= &stp_policy_node_item_ops,
+	.ct_group_ops	= &stp_policy_node_group_ops,
+	.ct_attrs	= stp_policy_node_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+/*
+ * Root group: policies.
+ */
+static struct configfs_attribute stp_policy_attr_device = {
+	.ca_owner = THIS_MODULE,
+	.ca_name = "device",
+	.ca_mode = S_IRUGO,
+};
+
+static struct configfs_attribute *stp_policy_attrs[] = {
+	&stp_policy_attr_device,
+	NULL,
+};
+
+static ssize_t stp_policy_attr_show(struct config_item *item,
+				    struct configfs_attribute *attr,
+				    char *page)
+{
+	struct stp_policy *policy = to_stp_policy(item);
+	ssize_t count;
+
+	count = sprintf(page, "%s\n",
+			(policy && policy->stm) ?
+			policy->stm->data->name :
+			"<none>");
+
+	return count;
+}
+
+void stp_policy_unbind(struct stp_policy *policy)
+{
+	struct stm_device *stm = policy->stm;
+
+	if (WARN_ON_ONCE(!policy->stm))
+		return;
+
+	mutex_lock(&stm->policy_mutex);
+	stm->policy = NULL;
+	mutex_unlock(&stm->policy_mutex);
+
+	policy->stm = NULL;
+
+	stm_put_device(stm);
+}
+
+static void stp_policy_release(struct config_item *item)
+{
+	struct stp_policy *policy = to_stp_policy(item);
+
+	stp_policy_unbind(policy);
+	kfree(policy);
+}
+
+static struct configfs_item_operations stp_policy_item_ops = {
+	.release		= stp_policy_release,
+	.show_attribute		= stp_policy_attr_show,
+};
+
+static struct configfs_group_operations stp_policy_group_ops = {
+	.make_group	= stp_policy_node_make,
+};
+
+static struct config_item_type stp_policy_type = {
+	.ct_item_ops	= &stp_policy_item_ops,
+	.ct_group_ops	= &stp_policy_group_ops,
+	.ct_attrs	= stp_policy_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_group *
+stp_policies_make(struct config_group *group, const char *name)
+{
+	struct config_group *ret;
+	struct stm_device *stm;
+	char *devname, *p;
+
+	devname = kasprintf(GFP_KERNEL, "%s", name);
+	if (!devname)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * node must look like <device_name>.<policy_name>, where
+	 * <device_name> is the name of an existing stm device and
+	 * <policy_name> is an arbitrary string
+	 */
+	p = strchr(devname, '.');
+	if (!p) {
+		kfree(devname);
+		return ERR_PTR(-EINVAL);
+	}
+
+	*p++ = '\0';
+
+	stm = stm_find_device(devname);
+	kfree(devname);
+
+	if (!stm)
+		return ERR_PTR(-ENODEV);
+
+	mutex_lock(&stm->policy_mutex);
+	if (stm->policy) {
+		ret = ERR_PTR(-EBUSY);
+		goto unlock_policy;
+	}
+
+	stm->policy = kzalloc(sizeof(*stm->policy), GFP_KERNEL);
+	if (!stm->policy) {
+		ret = ERR_PTR(-ENOMEM);
+		goto unlock_policy;
+	}
+
+	config_group_init_type_name(&stm->policy->group, name,
+				    &stp_policy_type);
+	stm->policy->stm = stm;
+
+	ret = &stm->policy->group;
+
+unlock_policy:
+	mutex_unlock(&stm->policy_mutex);
+
+	if (IS_ERR(ret))
+		stm_put_device(stm);
+
+	return ret;
+}
+
+static struct configfs_group_operations stp_policies_group_ops = {
+	.make_group	= stp_policies_make,
+};
+
+static struct config_item_type stp_policies_type = {
+	.ct_group_ops	= &stp_policies_group_ops,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct configfs_subsystem stp_policy_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf	= "stp-policy",
+			.ci_type	= &stp_policies_type,
+		},
+	},
+};
+
+/*
+ * Lock the policy mutex from the outside
+ */
+static struct stp_policy_node *
+__stp_policy_node_lookup(struct stp_policy *policy, char *s)
+{
+	struct stp_policy_node *policy_node, *ret;
+	struct list_head *head = &policy->group.cg_children;
+	struct config_item *item;
+	char *start, *end = s;
+
+	if (list_empty(head))
+		return NULL;
+
+	/* return the first entry if everything else fails */
+	item = list_entry(head->next, struct config_item, ci_entry);
+	ret = to_stp_policy_node(item);
+
+next:
+	for (;;) {
+		start = strsep(&end, "/");
+		if (!start)
+			break;
+
+		if (!*start)
+			continue;
+
+		list_for_each_entry(item, head, ci_entry) {
+			policy_node = to_stp_policy_node(item);
+
+			if (!strcmp(start,
+				    policy_node->group.cg_item.ci_name)) {
+				ret = policy_node;
+
+				if (!end)
+					goto out;
+
+				head = &policy_node->group.cg_children;
+				goto next;
+			}
+		}
+		break;
+	}
+
+out:
+	return ret;
+}
+
+
+struct stp_policy_node *
+stp_policy_node_lookup(struct stm_device *stm, char *s)
+{
+	struct stp_policy_node *policy_node = NULL;
+
+	mutex_lock(&stp_policy_subsys.su_mutex);
+
+	mutex_lock(&stm->policy_mutex);
+	if (stm->policy)
+		policy_node = __stp_policy_node_lookup(stm->policy, s);
+	mutex_unlock(&stm->policy_mutex);
+
+	if (policy_node)
+		config_item_get(&policy_node->group.cg_item);
+	mutex_unlock(&stp_policy_subsys.su_mutex);
+
+	return policy_node;
+}
+
+void stp_policy_node_put(struct stp_policy_node *policy_node)
+{
+	config_item_put(&policy_node->group.cg_item);
+}
+
+int __init stp_configfs_init(void)
+{
+	int err;
+
+	config_group_init(&stp_policy_subsys.su_group);
+	mutex_init(&stp_policy_subsys.su_mutex);
+	err = configfs_register_subsystem(&stp_policy_subsys);
+
+	return err;
+}
+
+void __exit stp_configfs_exit(void)
+{
+	configfs_unregister_subsystem(&stp_policy_subsys);
+}