linux/drivers/gpu/drm/i915/i915_pmu.c

/*
 * Copyright © 2017 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 */

#include <linux/perf_event.h>
#include <linux/pm_runtime.h>

#include "i915_drv.h"
#include "i915_pmu.h"
#include "intel_ringbuffer.h"

/* Frequency for the sampling timer for events which need it. */
#define FREQUENCY 200
#define PERIOD max_t(u64, 10000, NSEC_PER_SEC / FREQUENCY)

#define ENGINE_SAMPLE_MASK \
	(BIT(I915_SAMPLE_BUSY) | \
	 BIT(I915_SAMPLE_WAIT) | \
	 BIT(I915_SAMPLE_SEMA))

#define ENGINE_SAMPLE_BITS (1 << I915_PMU_SAMPLE_BITS)

static cpumask_t i915_pmu_cpumask;

static u8 engine_config_sample(u64 config)
{
	return config & I915_PMU_SAMPLE_MASK;
}

static u8 engine_event_sample(struct perf_event *event)
{
	return engine_config_sample(event->attr.config);
}

static u8 engine_event_class(struct perf_event *event)
{
	return (event->attr.config >> I915_PMU_CLASS_SHIFT) & 0xff;
}

static u8 engine_event_instance(struct perf_event *event)
{
	return (event->attr.config >> I915_PMU_SAMPLE_BITS) & 0xff;
}

static bool is_engine_config(u64 config)
{
	return config < __I915_PMU_OTHER(0);
}

static unsigned int config_enabled_bit(u64 config)
{
	if (is_engine_config(config))
		return engine_config_sample(config);
	else
		return ENGINE_SAMPLE_BITS + (config - __I915_PMU_OTHER(0));
}

static u64 config_enabled_mask(u64 config)
{
	return BIT_ULL(config_enabled_bit(config));
}

static bool is_engine_event(struct perf_event *event)
{
	return is_engine_config(event->attr.config);
}

static unsigned int event_enabled_bit(struct perf_event *event)
{
	return config_enabled_bit(event->attr.config);
}

static bool pmu_needs_timer(struct drm_i915_private *i915, bool gpu_active)
{
	u64 enable;

	/*
	 * Only some counters need the sampling timer.
	 *
	 * We start with a bitmask of all currently enabled events.
	 */
	enable = i915->pmu.enable;

	/*
	 * Mask out all the ones which do not need the timer, or in
	 * other words keep all the ones that could need the timer.
	 */
	enable &= config_enabled_mask(I915_PMU_ACTUAL_FREQUENCY) |
		  config_enabled_mask(I915_PMU_REQUESTED_FREQUENCY) |
		  ENGINE_SAMPLE_MASK;

	/*
	 * When the GPU is idle per-engine counters do not need to be
	 * running so clear those bits out.
	 */
	if (!gpu_active)
		enable &= ~ENGINE_SAMPLE_MASK;
	/*
	 * Also there is software busyness tracking available we do not
	 * need the timer for I915_SAMPLE_BUSY counter.
	 *
	 * Use RCS as proxy for all engines.
	 */
	else if (intel_engine_supports_stats(i915->engine[RCS]))
		enable &= ~BIT(I915_SAMPLE_BUSY);

	/*
	 * If some bits remain it means we need the sampling timer running.
	 */
	return enable;
}

void i915_pmu_gt_parked(struct drm_i915_private *i915)
{
	if (!i915->pmu.base.event_init)
		return;

	spin_lock_irq(&i915->pmu.lock);
	/*
	 * Signal sampling timer to stop if only engine events are enabled and
	 * GPU went idle.
	 */
	i915->pmu.timer_enabled = pmu_needs_timer(i915, false);
	spin_unlock_irq(&i915->pmu.lock);
}

static void __i915_pmu_maybe_start_timer(struct drm_i915_private *i915)
{
	if (!i915->pmu.timer_enabled && pmu_needs_timer(i915, true)) {
		i915->pmu.timer_enabled = true;
		hrtimer_start_range_ns(&i915->pmu.timer,
				       ns_to_ktime(PERIOD), 0,
				       HRTIMER_MODE_REL_PINNED);
	}
}

void i915_pmu_gt_unparked(struct drm_i915_private *i915)
{
	if (!i915->pmu.base.event_init)
		return;

	spin_lock_irq(&i915->pmu.lock);
	/*
	 * Re-enable sampling timer when GPU goes active.
	 */
	__i915_pmu_maybe_start_timer(i915);
	spin_unlock_irq(&i915->pmu.lock);
}

static bool grab_forcewake(struct drm_i915_private *i915, bool fw)
{
	if (!fw)
		intel_uncore_forcewake_get(i915, FORCEWAKE_ALL);

	return true;
}

static void
update_sample(struct i915_pmu_sample *sample, u32 unit, u32 val)
{
	sample->cur += mul_u32_u32(val, unit);
}

static void engines_sample(struct drm_i915_private *dev_priv)
{
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	bool fw = false;

	if ((dev_priv->pmu.enable & ENGINE_SAMPLE_MASK) == 0)
		return;

	if (!dev_priv->gt.awake)
		return;

	if (!intel_runtime_pm_get_if_in_use(dev_priv))
		return;

	for_each_engine(engine, dev_priv, id) {
		u32 current_seqno = intel_engine_get_seqno(engine);
		u32 last_seqno = intel_engine_last_submit(engine);
		u32 val;

		val = !i915_seqno_passed(current_seqno, last_seqno);

		update_sample(&engine->pmu.sample[I915_SAMPLE_BUSY],
			      PERIOD, val);

		if (val && (engine->pmu.enable &
		    (BIT(I915_SAMPLE_WAIT) | BIT(I915_SAMPLE_SEMA)))) {
			fw = grab_forcewake(dev_priv, fw);

			val = I915_READ_FW(RING_CTL(engine->mmio_base));
		} else {
			val = 0;
		}

		update_sample(&engine->pmu.sample[I915_SAMPLE_WAIT],
			      PERIOD, !!(val & RING_WAIT));

		update_sample(&engine->pmu.sample[I915_SAMPLE_SEMA],
			      PERIOD, !!(val & RING_WAIT_SEMAPHORE));
	}

	if (fw)
		intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);

	intel_runtime_pm_put(dev_priv);
}

static void frequency_sample(struct drm_i915_private *dev_priv)
{
	if (dev_priv->pmu.enable &
	    config_enabled_mask(I915_PMU_ACTUAL_FREQUENCY)) {
		u32 val;

		val = dev_priv->gt_pm.rps.cur_freq;
		if (dev_priv->gt.awake &&
		    intel_runtime_pm_get_if_in_use(dev_priv)) {
			val = intel_get_cagf(dev_priv,
					     I915_READ_NOTRACE(GEN6_RPSTAT1));
			intel_runtime_pm_put(dev_priv);
		}

		update_sample(&dev_priv->pmu.sample[__I915_SAMPLE_FREQ_ACT],
			      1, intel_gpu_freq(dev_priv, val));
	}

	if (dev_priv->pmu.enable &
	    config_enabled_mask(I915_PMU_REQUESTED_FREQUENCY)) {
		update_sample(&dev_priv->pmu.sample[__I915_SAMPLE_FREQ_REQ], 1,
			      intel_gpu_freq(dev_priv,
					     dev_priv->gt_pm.rps.cur_freq));
	}
}

static enum hrtimer_restart i915_sample(struct hrtimer *hrtimer)
{
	struct drm_i915_private *i915 =
		container_of(hrtimer, struct drm_i915_private, pmu.timer);

	if (!READ_ONCE(i915->pmu.timer_enabled))
		return HRTIMER_NORESTART;

	engines_sample(i915);
	frequency_sample(i915);

	hrtimer_forward_now(hrtimer, ns_to_ktime(PERIOD));
	return HRTIMER_RESTART;
}

static u64 count_interrupts(struct drm_i915_private *i915)
{
	/* open-coded kstat_irqs() */
	struct irq_desc *desc = irq_to_desc(i915->drm.pdev->irq);
	u64 sum = 0;
	int cpu;

	if (!desc || !desc->kstat_irqs)
		return 0;

	for_each_possible_cpu(cpu)
		sum += *per_cpu_ptr(desc->kstat_irqs, cpu);

	return sum;
}

static void i915_pmu_event_destroy(struct perf_event *event)
{
	WARN_ON(event->parent);
}

static int
engine_event_status(struct intel_engine_cs *engine,
		    enum drm_i915_pmu_engine_sample sample)
{
	switch (sample) {
	case I915_SAMPLE_BUSY:
	case I915_SAMPLE_WAIT:
		break;
	case I915_SAMPLE_SEMA:
		if (INTEL_GEN(engine->i915) < 6)
			return -ENODEV;
		break;
	default:
		return -ENOENT;
	}

	return 0;
}

static int
config_status(struct drm_i915_private *i915, u64 config)
{
	switch (config) {
	case I915_PMU_ACTUAL_FREQUENCY:
		if (IS_VALLEYVIEW(i915) || IS_CHERRYVIEW(i915))
			/* Requires a mutex for sampling! */
			return -ENODEV;
		/* Fall-through. */
	case I915_PMU_REQUESTED_FREQUENCY:
		if (INTEL_GEN(i915) < 6)
			return -ENODEV;
		break;
	case I915_PMU_INTERRUPTS:
		break;
	case I915_PMU_RC6_RESIDENCY:
		if (!HAS_RC6(i915))
			return -ENODEV;
		break;
	default:
		return -ENOENT;
	}

	return 0;
}

static int engine_event_init(struct perf_event *event)
{
	struct drm_i915_private *i915 =
		container_of(event->pmu, typeof(*i915), pmu.base);
	struct intel_engine_cs *engine;

	engine = intel_engine_lookup_user(i915, engine_event_class(event),
					  engine_event_instance(event));
	if (!engine)
		return -ENODEV;

	return engine_event_status(engine, engine_event_sample(event));
}

static int i915_pmu_event_init(struct perf_event *event)
{
	struct drm_i915_private *i915 =
		container_of(event->pmu, typeof(*i915), pmu.base);
	int ret;

	if (event->attr.type != event->pmu->type)
		return -ENOENT;

	/* unsupported modes and filters */
	if (event->attr.sample_period) /* no sampling */
		return -EINVAL;

	if (has_branch_stack(event))
		return -EOPNOTSUPP;

	if (event->cpu < 0)
		return -EINVAL;

	/* only allow running on one cpu at a time */
	if (!cpumask_test_cpu(event->cpu, &i915_pmu_cpumask))
		return -EINVAL;

	if (is_engine_event(event))
		ret = engine_event_init(event);
	else
		ret = config_status(i915, event->attr.config);
	if (ret)
		return ret;

	if (!event->parent)
		event->destroy = i915_pmu_event_destroy;

	return 0;
}

static u64 __i915_pmu_event_read(struct perf_event *event)
{
	struct drm_i915_private *i915 =
		container_of(event->pmu, typeof(*i915), pmu.base);
	u64 val = 0;

	if (is_engine_event(event)) {
		u8 sample = engine_event_sample(event);
		struct intel_engine_cs *engine;

		engine = intel_engine_lookup_user(i915,
						  engine_event_class(event),
						  engine_event_instance(event));

		if (WARN_ON_ONCE(!engine)) {
			/* Do nothing */
		} else if (sample == I915_SAMPLE_BUSY &&
			   engine->pmu.busy_stats) {
			val = ktime_to_ns(intel_engine_get_busy_time(engine));
		} else {
			val = engine->pmu.sample[sample].cur;
		}
	} else {
		switch (event->attr.config) {
		case I915_PMU_ACTUAL_FREQUENCY:
			val =
			   div_u64(i915->pmu.sample[__I915_SAMPLE_FREQ_ACT].cur,
				   FREQUENCY);
			break;
		case I915_PMU_REQUESTED_FREQUENCY:
			val =
			   div_u64(i915->pmu.sample[__I915_SAMPLE_FREQ_REQ].cur,
				   FREQUENCY);
			break;
		case I915_PMU_INTERRUPTS:
			val = count_interrupts(i915);
			break;
		case I915_PMU_RC6_RESIDENCY:
			intel_runtime_pm_get(i915);
			val = intel_rc6_residency_ns(i915,
						     IS_VALLEYVIEW(i915) ?
						     VLV_GT_RENDER_RC6 :
						     GEN6_GT_GFX_RC6);
			if (HAS_RC6p(i915))
				val += intel_rc6_residency_ns(i915,
							      GEN6_GT_GFX_RC6p);
			if (HAS_RC6pp(i915))
				val += intel_rc6_residency_ns(i915,
							      GEN6_GT_GFX_RC6pp);
			intel_runtime_pm_put(i915);
			break;
		}
	}

	return val;
}

static void i915_pmu_event_read(struct perf_event *event)
{
	struct hw_perf_event *hwc = &event->hw;
	u64 prev, new;

again:
	prev = local64_read(&hwc->prev_count);
	new = __i915_pmu_event_read(event);

	if (local64_cmpxchg(&hwc->prev_count, prev, new) != prev)
		goto again;

	local64_add(new - prev, &event->count);
}

static bool engine_needs_busy_stats(struct intel_engine_cs *engine)
{
	return intel_engine_supports_stats(engine) &&
	       (engine->pmu.enable & BIT(I915_SAMPLE_BUSY));
}

static void i915_pmu_enable(struct perf_event *event)
{
	struct drm_i915_private *i915 =
		container_of(event->pmu, typeof(*i915), pmu.base);
	unsigned int bit = event_enabled_bit(event);
	unsigned long flags;

	spin_lock_irqsave(&i915->pmu.lock, flags);

	/*
	 * Update the bitmask of enabled events and increment
	 * the event reference counter.
	 */
	GEM_BUG_ON(bit >= I915_PMU_MASK_BITS);
	GEM_BUG_ON(i915->pmu.enable_count[bit] == ~0);
	i915->pmu.enable |= BIT_ULL(bit);
	i915->pmu.enable_count[bit]++;

	/*
	 * Start the sampling timer if needed and not already enabled.
	 */
	__i915_pmu_maybe_start_timer(i915);

	/*
	 * For per-engine events the bitmask and reference counting
	 * is stored per engine.
	 */
	if (is_engine_event(event)) {
		u8 sample = engine_event_sample(event);
		struct intel_engine_cs *engine;

		engine = intel_engine_lookup_user(i915,
						  engine_event_class(event),
						  engine_event_instance(event));
		GEM_BUG_ON(!engine);
		engine->pmu.enable |= BIT(sample);

		GEM_BUG_ON(sample >= I915_PMU_SAMPLE_BITS);
		GEM_BUG_ON(engine->pmu.enable_count[sample] == ~0);
		if (engine->pmu.enable_count[sample]++ == 0) {
			/*
			 * Enable engine busy stats tracking if needed or
			 * alternatively cancel the scheduled disable.
			 *
			 * If the delayed disable was pending, cancel it and
			 * in this case do not enable since it already is.
			 */
			if (engine_needs_busy_stats(engine) &&
			    !engine->pmu.busy_stats) {
				engine->pmu.busy_stats = true;
				if (!cancel_delayed_work(&engine->pmu.disable_busy_stats))
					intel_enable_engine_stats(engine);
			}
		}
	}

	/*
	 * Store the current counter value so we can report the correct delta
	 * for all listeners. Even when the event was already enabled and has
	 * an existing non-zero value.
	 */
	local64_set(&event->hw.prev_count, __i915_pmu_event_read(event));

	spin_unlock_irqrestore(&i915->pmu.lock, flags);
}

static void __disable_busy_stats(struct work_struct *work)
{
	struct intel_engine_cs *engine =
	       container_of(work, typeof(*engine), pmu.disable_busy_stats.work);

	intel_disable_engine_stats(engine);
}

static void i915_pmu_disable(struct perf_event *event)
{
	struct drm_i915_private *i915 =
		container_of(event->pmu, typeof(*i915), pmu.base);
	unsigned int bit = event_enabled_bit(event);
	unsigned long flags;

	spin_lock_irqsave(&i915->pmu.lock, flags);

	if (is_engine_event(event)) {
		u8 sample = engine_event_sample(event);
		struct intel_engine_cs *engine;

		engine = intel_engine_lookup_user(i915,
						  engine_event_class(event),
						  engine_event_instance(event));
		GEM_BUG_ON(!engine);
		GEM_BUG_ON(sample >= I915_PMU_SAMPLE_BITS);
		GEM_BUG_ON(engine->pmu.enable_count[sample] == 0);
		/*
		 * Decrement the reference count and clear the enabled
		 * bitmask when the last listener on an event goes away.
		 */
		if (--engine->pmu.enable_count[sample] == 0) {
			engine->pmu.enable &= ~BIT(sample);
			if (!engine_needs_busy_stats(engine) &&
			    engine->pmu.busy_stats) {
				engine->pmu.busy_stats = false;
				/*
				 * We request a delayed disable to handle the
				 * rapid on/off cycles on events, which can
				 * happen when tools like perf stat start, in a
				 * nicer way.
				 *
				 * In addition, this also helps with busy stats
				 * accuracy with background CPU offline/online
				 * migration events.
				 */
				queue_delayed_work(system_wq,
						   &engine->pmu.disable_busy_stats,
						   round_jiffies_up_relative(HZ));
			}
		}
	}

	GEM_BUG_ON(bit >= I915_PMU_MASK_BITS);
	GEM_BUG_ON(i915->pmu.enable_count[bit] == 0);
	/*
	 * Decrement the reference count and clear the enabled
	 * bitmask when the last listener on an event goes away.
	 */
	if (--i915->pmu.enable_count[bit] == 0) {
		i915->pmu.enable &= ~BIT_ULL(bit);
		i915->pmu.timer_enabled &= pmu_needs_timer(i915, true);
	}

	spin_unlock_irqrestore(&i915->pmu.lock, flags);
}

static void i915_pmu_event_start(struct perf_event *event, int flags)
{
	i915_pmu_enable(event);
	event->hw.state = 0;
}

static void i915_pmu_event_stop(struct perf_event *event, int flags)
{
	if (flags & PERF_EF_UPDATE)
		i915_pmu_event_read(event);
	i915_pmu_disable(event);
	event->hw.state = PERF_HES_STOPPED;
}

static int i915_pmu_event_add(struct perf_event *event, int flags)
{
	if (flags & PERF_EF_START)
		i915_pmu_event_start(event, flags);

	return 0;
}

static void i915_pmu_event_del(struct perf_event *event, int flags)
{
	i915_pmu_event_stop(event, PERF_EF_UPDATE);
}

static int i915_pmu_event_event_idx(struct perf_event *event)
{
	return 0;
}

struct i915_str_attribute {
	struct device_attribute attr;
	const char *str;
};

static ssize_t i915_pmu_format_show(struct device *dev,
				    struct device_attribute *attr, char *buf)
{
	struct i915_str_attribute *eattr;

	eattr = container_of(attr, struct i915_str_attribute, attr);
	return sprintf(buf, "%s\n", eattr->str);
}

#define I915_PMU_FORMAT_ATTR(_name, _config) \
	(&((struct i915_str_attribute[]) { \
		{ .attr = __ATTR(_name, 0444, i915_pmu_format_show, NULL), \
		  .str = _config, } \
	})[0].attr.attr)

static struct attribute *i915_pmu_format_attrs[] = {
	I915_PMU_FORMAT_ATTR(i915_eventid, "config:0-20"),
	NULL,
};

static const struct attribute_group i915_pmu_format_attr_group = {
	.name = "format",
	.attrs = i915_pmu_format_attrs,
};

struct i915_ext_attribute {
	struct device_attribute attr;
	unsigned long val;
};

static ssize_t i915_pmu_event_show(struct device *dev,
				   struct device_attribute *attr, char *buf)
{
	struct i915_ext_attribute *eattr;

	eattr = container_of(attr, struct i915_ext_attribute, attr);
	return sprintf(buf, "config=0x%lx\n", eattr->val);
}

static struct attribute_group i915_pmu_events_attr_group = {
	.name = "events",
	/* Patch in attrs at runtime. */
};

static ssize_t
i915_pmu_get_attr_cpumask(struct device *dev,
			  struct device_attribute *attr,
			  char *buf)
{
	return cpumap_print_to_pagebuf(true, buf, &i915_pmu_cpumask);
}

static DEVICE_ATTR(cpumask, 0444, i915_pmu_get_attr_cpumask, NULL);

static struct attribute *i915_cpumask_attrs[] = {
	&dev_attr_cpumask.attr,
	NULL,
};

static const struct attribute_group i915_pmu_cpumask_attr_group = {
	.attrs = i915_cpumask_attrs,
};

static const struct attribute_group *i915_pmu_attr_groups[] = {
	&i915_pmu_format_attr_group,
	&i915_pmu_events_attr_group,
	&i915_pmu_cpumask_attr_group,
	NULL
};

#define __event(__config, __name, __unit) \
{ \
	.config = (__config), \
	.name = (__name), \
	.unit = (__unit), \
}

#define __engine_event(__sample, __name) \
{ \
	.sample = (__sample), \
	.name = (__name), \
}

static struct i915_ext_attribute *
add_i915_attr(struct i915_ext_attribute *attr, const char *name, u64 config)
{
	sysfs_attr_init(&attr->attr.attr);
	attr->attr.attr.name = name;
	attr->attr.attr.mode = 0444;
	attr->attr.show = i915_pmu_event_show;
	attr->val = config;

	return ++attr;
}

static struct perf_pmu_events_attr *
add_pmu_attr(struct perf_pmu_events_attr *attr, const char *name,
	     const char *str)
{
	sysfs_attr_init(&attr->attr.attr);
	attr->attr.attr.name = name;
	attr->attr.attr.mode = 0444;
	attr->attr.show = perf_event_sysfs_show;
	attr->event_str = str;

	return ++attr;
}

static struct attribute **
create_event_attributes(struct drm_i915_private *i915)
{
	static const struct {
		u64 config;
		const char *name;
		const char *unit;
	} events[] = {
		__event(I915_PMU_ACTUAL_FREQUENCY, "actual-frequency", "MHz"),
		__event(I915_PMU_REQUESTED_FREQUENCY, "requested-frequency", "MHz"),
		__event(I915_PMU_INTERRUPTS, "interrupts", NULL),
		__event(I915_PMU_RC6_RESIDENCY, "rc6-residency", "ns"),
	};
	static const struct {
		enum drm_i915_pmu_engine_sample sample;
		char *name;
	} engine_events[] = {
		__engine_event(I915_SAMPLE_BUSY, "busy"),
		__engine_event(I915_SAMPLE_SEMA, "sema"),
		__engine_event(I915_SAMPLE_WAIT, "wait"),
	};
	unsigned int count = 0;
	struct perf_pmu_events_attr *pmu_attr = NULL, *pmu_iter;
	struct i915_ext_attribute *i915_attr = NULL, *i915_iter;
	struct attribute **attr = NULL, **attr_iter;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	unsigned int i;

	/* Count how many counters we will be exposing. */
	for (i = 0; i < ARRAY_SIZE(events); i++) {
		if (!config_status(i915, events[i].config))
			count++;
	}

	for_each_engine(engine, i915, id) {
		for (i = 0; i < ARRAY_SIZE(engine_events); i++) {
			if (!engine_event_status(engine,
						 engine_events[i].sample))
				count++;
		}
	}

	/* Allocate attribute objects and table. */
	i915_attr = kzalloc(count * sizeof(*i915_attr), GFP_KERNEL);
	if (!i915_attr)
		goto err_alloc;

	pmu_attr = kzalloc(count * sizeof(*pmu_attr), GFP_KERNEL);
	if (!pmu_attr)
		goto err_alloc;

	/* Max one pointer of each attribute type plus a termination entry. */
	attr = kzalloc((count * 2 + 1) * sizeof(attr), GFP_KERNEL);
	if (!attr)
		goto err_alloc;

	i915_iter = i915_attr;
	pmu_iter = pmu_attr;
	attr_iter = attr;

	/* Initialize supported non-engine counters. */
	for (i = 0; i < ARRAY_SIZE(events); i++) {
		char *str;

		if (config_status(i915, events[i].config))
			continue;

		str = kstrdup(events[i].name, GFP_KERNEL);
		if (!str)
			goto err;

		*attr_iter++ = &i915_iter->attr.attr;
		i915_iter = add_i915_attr(i915_iter, str, events[i].config);

		if (events[i].unit) {
			str = kasprintf(GFP_KERNEL, "%s.unit", events[i].name);
			if (!str)
				goto err;

			*attr_iter++ = &pmu_iter->attr.attr;
			pmu_iter = add_pmu_attr(pmu_iter, str, events[i].unit);
		}
	}

	/* Initialize supported engine counters. */
	for_each_engine(engine, i915, id) {
		for (i = 0; i < ARRAY_SIZE(engine_events); i++) {
			char *str;

			if (engine_event_status(engine,
						engine_events[i].sample))
				continue;

			str = kasprintf(GFP_KERNEL, "%s-%s",
					engine->name, engine_events[i].name);
			if (!str)
				goto err;

			*attr_iter++ = &i915_iter->attr.attr;
			i915_iter =
				add_i915_attr(i915_iter, str,
					      __I915_PMU_ENGINE(engine->class,
								engine->instance,
								engine_events[i].sample));

			str = kasprintf(GFP_KERNEL, "%s-%s.unit",
					engine->name, engine_events[i].name);
			if (!str)
				goto err;

			*attr_iter++ = &pmu_iter->attr.attr;
			pmu_iter = add_pmu_attr(pmu_iter, str, "ns");
		}
	}

	i915->pmu.i915_attr = i915_attr;
	i915->pmu.pmu_attr = pmu_attr;

	return attr;

err:;
	for (attr_iter = attr; *attr_iter; attr_iter++)
		kfree((*attr_iter)->name);

err_alloc:
	kfree(attr);
	kfree(i915_attr);
	kfree(pmu_attr);

	return NULL;
}

static void free_event_attributes(struct drm_i915_private *i915)
{
	struct attribute **attr_iter = i915_pmu_events_attr_group.attrs;

	for (; *attr_iter; attr_iter++)
		kfree((*attr_iter)->name);

	kfree(i915_pmu_events_attr_group.attrs);
	kfree(i915->pmu.i915_attr);
	kfree(i915->pmu.pmu_attr);

	i915_pmu_events_attr_group.attrs = NULL;
	i915->pmu.i915_attr = NULL;
	i915->pmu.pmu_attr = NULL;
}

static int i915_pmu_cpu_online(unsigned int cpu, struct hlist_node *node)
{
	struct i915_pmu *pmu = hlist_entry_safe(node, typeof(*pmu), node);

	GEM_BUG_ON(!pmu->base.event_init);

	/* Select the first online CPU as a designated reader. */
	if (!cpumask_weight(&i915_pmu_cpumask))
		cpumask_set_cpu(cpu, &i915_pmu_cpumask);

	return 0;
}

static int i915_pmu_cpu_offline(unsigned int cpu, struct hlist_node *node)
{
	struct i915_pmu *pmu = hlist_entry_safe(node, typeof(*pmu), node);
	unsigned int target;

	GEM_BUG_ON(!pmu->base.event_init);

	if (cpumask_test_and_clear_cpu(cpu, &i915_pmu_cpumask)) {
		target = cpumask_any_but(topology_sibling_cpumask(cpu), cpu);
		/* Migrate events if there is a valid target */
		if (target < nr_cpu_ids) {
			cpumask_set_cpu(target, &i915_pmu_cpumask);
			perf_pmu_migrate_context(&pmu->base, cpu, target);
		}
	}

	return 0;
}

static enum cpuhp_state cpuhp_slot = CPUHP_INVALID;

static int i915_pmu_register_cpuhp_state(struct drm_i915_private *i915)
{
	enum cpuhp_state slot;
	int ret;

	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
				      "perf/x86/intel/i915:online",
				      i915_pmu_cpu_online,
				      i915_pmu_cpu_offline);
	if (ret < 0)
		return ret;

	slot = ret;
	ret = cpuhp_state_add_instance(slot, &i915->pmu.node);
	if (ret) {
		cpuhp_remove_multi_state(slot);
		return ret;
	}

	cpuhp_slot = slot;
	return 0;
}

static void i915_pmu_unregister_cpuhp_state(struct drm_i915_private *i915)
{
	WARN_ON(cpuhp_slot == CPUHP_INVALID);
	WARN_ON(cpuhp_state_remove_instance(cpuhp_slot, &i915->pmu.node));
	cpuhp_remove_multi_state(cpuhp_slot);
}

void i915_pmu_register(struct drm_i915_private *i915)
{
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	int ret;

	if (INTEL_GEN(i915) <= 2) {
		DRM_INFO("PMU not supported for this GPU.");
		return;
	}

	i915_pmu_events_attr_group.attrs = create_event_attributes(i915);
	if (!i915_pmu_events_attr_group.attrs) {
		ret = -ENOMEM;
		goto err;
	}

	i915->pmu.base.attr_groups	= i915_pmu_attr_groups;
	i915->pmu.base.task_ctx_nr	= perf_invalid_context;
	i915->pmu.base.event_init	= i915_pmu_event_init;
	i915->pmu.base.add		= i915_pmu_event_add;
	i915->pmu.base.del		= i915_pmu_event_del;
	i915->pmu.base.start		= i915_pmu_event_start;
	i915->pmu.base.stop		= i915_pmu_event_stop;
	i915->pmu.base.read		= i915_pmu_event_read;
	i915->pmu.base.event_idx	= i915_pmu_event_event_idx;

	spin_lock_init(&i915->pmu.lock);
	hrtimer_init(&i915->pmu.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	i915->pmu.timer.function = i915_sample;

	for_each_engine(engine, i915, id)
		INIT_DELAYED_WORK(&engine->pmu.disable_busy_stats,
				  __disable_busy_stats);

	ret = perf_pmu_register(&i915->pmu.base, "i915", -1);
	if (ret)
		goto err;

	ret = i915_pmu_register_cpuhp_state(i915);
	if (ret)
		goto err_unreg;

	return;

err_unreg:
	perf_pmu_unregister(&i915->pmu.base);
err:
	i915->pmu.base.event_init = NULL;
	free_event_attributes(i915);
	DRM_NOTE("Failed to register PMU! (err=%d)\n", ret);
}

void i915_pmu_unregister(struct drm_i915_private *i915)
{
	struct intel_engine_cs *engine;
	enum intel_engine_id id;

	if (!i915->pmu.base.event_init)
		return;

	WARN_ON(i915->pmu.enable);

	hrtimer_cancel(&i915->pmu.timer);

	for_each_engine(engine, i915, id) {
		GEM_BUG_ON(engine->pmu.busy_stats);
		flush_delayed_work(&engine->pmu.disable_busy_stats);
	}

	i915_pmu_unregister_cpuhp_state(i915);

	perf_pmu_unregister(&i915->pmu.base);
	i915->pmu.base.event_init = NULL;
	free_event_attributes(i915);
}