[RFC 5/5] drm/i915: Add sysfs toggle to enable per-client engine stats

[Tvrtko Ursulin <tursulin@ursulin.net>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

By default we are not collecting any per-engine and per-context
statistcs.

Add a new sysfs toggle to enable this facility:

$ echo 1 >/sys/class/drm/card0/clients/enable_stats

v2: Rebase.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h   |  2 ++
 drivers/gpu/drm/i915/i915_sysfs.c | 72 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d6b2883b42fe..fe8d91ce2af5 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2385,6 +2385,8 @@ struct drm_i915_private {
 
 	struct kobject *clients_root;
 	atomic_t client_serial;
+	struct device_attribute client_stats_attr;
+	bool client_stats_enabled;
 
 	/*
 	 * NOTE: This is the dri1/ums dungeon, don't add stuff here. Your patch
diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
index 6cf032bc1573..2eb720042007 100644
--- a/drivers/gpu/drm/i915/i915_sysfs.c
+++ b/drivers/gpu/drm/i915/i915_sysfs.c
@@ -570,9 +570,67 @@ static void i915_setup_error_capture(struct device *kdev) {}
 static void i915_teardown_error_capture(struct device *kdev) {}
 #endif
 
+static ssize_t
+show_client_stats(struct device *kdev, struct device_attribute *attr, char *buf)
+{
+	struct drm_i915_private *i915 =
+		container_of(attr, struct drm_i915_private, client_stats_attr);
+
+	return snprintf(buf, PAGE_SIZE, "%u\n", i915->client_stats_enabled);
+}
+
+static ssize_t
+store_client_stats(struct device *kdev, struct device_attribute *attr,
+		   const char *buf, size_t count)
+{
+	struct drm_i915_private *i915 =
+		container_of(attr, struct drm_i915_private, client_stats_attr);
+	bool disable = false;
+	bool enable = false;
+	bool val = false;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	int ret;
+
+	 /* Use RCS as proxy for all engines. */
+	if (!intel_engine_supports_stats(i915->engine[RCS]))
+		return -EINVAL;
+
+	ret = kstrtobool(buf, &val);
+	if (ret)
+		return ret;
+
+	ret = i915_mutex_lock_interruptible(&i915->drm);
+	if (ret)
+		return ret;
+
+	if (val && !i915->client_stats_enabled)
+		enable = true;
+	else if (!val && i915->client_stats_enabled)
+		disable = true;
+
+	if (!enable && !disable)
+		goto out;
+
+	for_each_engine(engine, i915, id) {
+		if (enable)
+			WARN_ON_ONCE(intel_enable_engine_stats(engine));
+		else if (disable)
+			intel_disable_engine_stats(engine);
+	}
+
+	i915->client_stats_enabled = val;
+
+out:
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	return count;
+}
+
 void i915_setup_sysfs(struct drm_i915_private *dev_priv)
 {
 	struct device *kdev = dev_priv->drm.primary->kdev;
+	struct device_attribute *attr;
 	int ret;
 
 	dev_priv->clients_root =
@@ -580,6 +638,17 @@ void i915_setup_sysfs(struct drm_i915_private *dev_priv)
 	if (!dev_priv->clients_root)
 		DRM_ERROR("Per-client sysfs setup failed\n");
 
+	attr = &dev_priv->client_stats_attr;
+	attr->attr.name = "enable_stats";
+	attr->attr.mode = 0664;
+	attr->show = show_client_stats;
+	attr->store = store_client_stats;
+
+	ret = sysfs_create_file(dev_priv->clients_root,
+				(struct attribute *)attr);
+	if (ret)
+		DRM_ERROR("Per-client sysfs setup failed! (%d)\n", ret);
+
 #ifdef CONFIG_PM
 	if (HAS_RC6(dev_priv)) {
 		ret = sysfs_merge_group(&kdev->kobj,
@@ -641,6 +710,9 @@ void i915_teardown_sysfs(struct drm_i915_private *dev_priv)
 	sysfs_unmerge_group(&kdev->kobj, &rc6p_attr_group);
 #endif
 
+	sysfs_remove_file(dev_priv->clients_root,
+			  (struct attribute *)&dev_priv->client_stats_attr);
+
 	if (dev_priv->clients_root)
 		kobject_put(dev_priv->clients_root);
 }
-- 
2.14.1

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