drm/i915: Show per-engine default property values in sysfs

By providing the default values configured into the kernel via sysfs, it
is much more convenient for userspace to restore those sane defaults, or
at least know what are considered good baseline. This is useful, for
example, to cleanup after any failed userspace prior to commencing new
jobs.

/sys/class/drm/card0/engine/rcs0/
├── capabilities
├── class
├── .defaults
│   ├── heartbeat_interval_ms
│   ├── max_busywait_duration_ns
│   ├── preempt_timeout_ms
│   ├── stop_timeout_ms
│   └── timeslice_duration_ms
├── heartbeat_interval_ms
├── instance
├── known_capabilities
├── max_busywait_duration_ns
├── mmio_base
├── name
├── preempt_timeout_ms
├── stop_timeout_ms
└── timeslice_duration_ms
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Maciej Patelczyk <maciej.patelczyk@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200514062905.28668-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_engine_cs.c

@@ -326,6 +326,8 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id)
 	if (INTEL_GEN(i915) == 12 && engine->class == RENDER_CLASS)
 		engine->props.preempt_timeout_ms = 0;
 
+	engine->defaults = engine->props; /* never to change again */
+
 	engine->context_size = intel_engine_context_size(gt, engine->class);
 	if (WARN_ON(engine->context_size > BIT(20)))
 		engine->context_size = 0;

drivers/gpu/drm/i915/gt/intel_engine_types.h

@@ -565,7 +565,7 @@ struct intel_engine_cs {
 		unsigned long preempt_timeout_ms;
 		unsigned long stop_timeout_ms;
 		unsigned long timeslice_duration_ms;
-	} props;
+	} props, defaults;
 };
 
 static inline bool

drivers/gpu/drm/i915/gt/sysfs_engines.c

@@ -191,6 +191,17 @@ max_spin_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 static struct kobj_attribute max_spin_attr =
 __ATTR(max_busywait_duration_ns, 0644, max_spin_show, max_spin_store);
 
+static ssize_t
+max_spin_default(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	struct intel_engine_cs *engine = kobj_to_engine(kobj);
+
+	return sprintf(buf, "%lu\n", engine->defaults.max_busywait_duration_ns);
+}
+
+static struct kobj_attribute max_spin_def =
+__ATTR(max_busywait_duration_ns, 0444, max_spin_default, NULL);
+
 static ssize_t
 timeslice_store(struct kobject *kobj, struct kobj_attribute *attr,
 		const char *buf, size_t count)
@@ -233,6 +244,17 @@ timeslice_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 static struct kobj_attribute timeslice_duration_attr =
 __ATTR(timeslice_duration_ms, 0644, timeslice_show, timeslice_store);
 
+static ssize_t
+timeslice_default(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	struct intel_engine_cs *engine = kobj_to_engine(kobj);
+
+	return sprintf(buf, "%lu\n", engine->defaults.timeslice_duration_ms);
+}
+
+static struct kobj_attribute timeslice_duration_def =
+__ATTR(timeslice_duration_ms, 0444, timeslice_default, NULL);
+
 static ssize_t
 stop_store(struct kobject *kobj, struct kobj_attribute *attr,
 	   const char *buf, size_t count)
@@ -272,6 +294,17 @@ stop_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 static struct kobj_attribute stop_timeout_attr =
 __ATTR(stop_timeout_ms, 0644, stop_show, stop_store);
 
+static ssize_t
+stop_default(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	struct intel_engine_cs *engine = kobj_to_engine(kobj);
+
+	return sprintf(buf, "%lu\n", engine->defaults.stop_timeout_ms);
+}
+
+static struct kobj_attribute stop_timeout_def =
+__ATTR(stop_timeout_ms, 0444, stop_default, NULL);
+
 static ssize_t
 preempt_timeout_store(struct kobject *kobj, struct kobj_attribute *attr,
 		      const char *buf, size_t count)
@@ -316,6 +349,18 @@ preempt_timeout_show(struct kobject *kobj, struct kobj_attribute *attr,
 static struct kobj_attribute preempt_timeout_attr =
 __ATTR(preempt_timeout_ms, 0644, preempt_timeout_show, preempt_timeout_store);
 
+static ssize_t
+preempt_timeout_default(struct kobject *kobj, struct kobj_attribute *attr,
+			char *buf)
+{
+	struct intel_engine_cs *engine = kobj_to_engine(kobj);
+
+	return sprintf(buf, "%lu\n", engine->defaults.preempt_timeout_ms);
+}
+
+static struct kobj_attribute preempt_timeout_def =
+__ATTR(preempt_timeout_ms, 0444, preempt_timeout_default, NULL);
+
 static ssize_t
 heartbeat_store(struct kobject *kobj, struct kobj_attribute *attr,
 		const char *buf, size_t count)
@@ -359,6 +404,17 @@ heartbeat_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 static struct kobj_attribute heartbeat_interval_attr =
 __ATTR(heartbeat_interval_ms, 0644, heartbeat_show, heartbeat_store);
 
+static ssize_t
+heartbeat_default(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	struct intel_engine_cs *engine = kobj_to_engine(kobj);
+
+	return sprintf(buf, "%lu\n", engine->defaults.heartbeat_interval_ms);
+}
+
+static struct kobj_attribute heartbeat_interval_def =
+__ATTR(heartbeat_interval_ms, 0444, heartbeat_default, NULL);
+
 static void kobj_engine_release(struct kobject *kobj)
 {
 	kfree(kobj);
@@ -390,6 +446,42 @@ kobj_engine(struct kobject *dir, struct intel_engine_cs *engine)
 	return &ke->base;
 }
 
+static void add_defaults(struct kobj_engine *parent)
+{
+	static const struct attribute *files[] = {
+		&max_spin_def.attr,
+		&stop_timeout_def.attr,
+#if CONFIG_DRM_I915_HEARTBEAT_INTERVAL
+		&heartbeat_interval_def.attr,
+#endif
+		NULL
+	};
+	struct kobj_engine *ke;
+
+	ke = kzalloc(sizeof(*ke), GFP_KERNEL);
+	if (!ke)
+		return;
+
+	kobject_init(&ke->base, &kobj_engine_type);
+	ke->engine = parent->engine;
+
+	if (kobject_add(&ke->base, &parent->base, "%s", ".defaults")) {
+		kobject_put(&ke->base);
+		return;
+	}
+
+	if (sysfs_create_files(&ke->base, files))
+		return;
+
+	if (intel_engine_has_timeslices(ke->engine) &&
+	    sysfs_create_file(&ke->base, &timeslice_duration_def.attr))
+		return;
+
+	if (intel_engine_has_preempt_reset(ke->engine) &&
+	    sysfs_create_file(&ke->base, &preempt_timeout_def.attr))
+		return;
+}
+
 void intel_engines_add_sysfs(struct drm_i915_private *i915)
 {
 	static const struct attribute *files[] = {
@@ -433,6 +525,8 @@ void intel_engines_add_sysfs(struct drm_i915_private *i915)
 		    sysfs_create_file(kobj, &preempt_timeout_attr.attr))
 			goto err_engine;
 
+		add_defaults(container_of(kobj, struct kobj_engine, base));
+
 		if (0) {
 err_object:
 			kobject_put(kobj);