apple_m1_cpu_pmu.c

// SPDX-License-Identifier: GPL-2.0
/*
 * CPU PMU driver for the Apple M1 and derivatives
 *
 * Copyright (C) 2021 Google LLC
 *
 * Author: Marc Zyngier <maz@kernel.org>
 *
 * Most of the information used in this driver was provided by the
 * Asahi Linux project. The rest was experimentally discovered.
 */

#include <linux/of.h>
#include <linux/perf/arm_pmu.h>
#include <linux/platform_device.h>

#include <asm/apple_m1_pmu.h>
#include <asm/irq_regs.h>
#include <asm/perf_event.h>

#define M1_PMU_NR_COUNTERS		10

#define M1_PMU_CFG_EVENT		GENMASK(7, 0)

#define ANY_BUT_0_1			GENMASK(9, 2)
#define ONLY_2_TO_7			GENMASK(7, 2)
#define ONLY_2_4_6			(BIT(2) | BIT(4) | BIT(6))
#define ONLY_5_6_7			(BIT(5) | BIT(6) | BIT(7))

/*
 * Description of the events we actually know about, as well as those with
 * a specific counter affinity. Yes, this is a grand total of two known
 * counters, and the rest is anybody's guess.
 *
 * Not all counters can count all events. Counters #0 and #1 are wired to
 * count cycles and instructions respectively, and some events have
 * bizarre mappings (every other counter, or even *one* counter). These
 * restrictions equally apply to both P and E cores.
 *
 * It is worth noting that the PMUs attached to P and E cores are likely
 * to be different because the underlying uarches are different. At the
 * moment, we don't really need to distinguish between the two because we
 * know next to nothing about the events themselves, and we already have
 * per cpu-type PMU abstractions.
 *
 * If we eventually find out that the events are different across
 * implementations, we'll have to introduce per cpu-type tables.
 */
enum m1_pmu_events {
	M1_PMU_PERFCTR_UNKNOWN_01	= 0x01,
	M1_PMU_PERFCTR_CPU_CYCLES	= 0x02,
	M1_PMU_PERFCTR_INSTRUCTIONS	= 0x8c,
	M1_PMU_PERFCTR_UNKNOWN_8d	= 0x8d,
	M1_PMU_PERFCTR_UNKNOWN_8e	= 0x8e,
	M1_PMU_PERFCTR_UNKNOWN_8f	= 0x8f,
	M1_PMU_PERFCTR_UNKNOWN_90	= 0x90,
	M1_PMU_PERFCTR_UNKNOWN_93	= 0x93,
	M1_PMU_PERFCTR_UNKNOWN_94	= 0x94,
	M1_PMU_PERFCTR_UNKNOWN_95	= 0x95,
	M1_PMU_PERFCTR_UNKNOWN_96	= 0x96,
	M1_PMU_PERFCTR_UNKNOWN_97	= 0x97,
	M1_PMU_PERFCTR_UNKNOWN_98	= 0x98,
	M1_PMU_PERFCTR_UNKNOWN_99	= 0x99,
	M1_PMU_PERFCTR_UNKNOWN_9a	= 0x9a,
	M1_PMU_PERFCTR_UNKNOWN_9b	= 0x9b,
	M1_PMU_PERFCTR_UNKNOWN_9c	= 0x9c,
	M1_PMU_PERFCTR_UNKNOWN_9f	= 0x9f,
	M1_PMU_PERFCTR_UNKNOWN_bf	= 0xbf,
	M1_PMU_PERFCTR_UNKNOWN_c0	= 0xc0,
	M1_PMU_PERFCTR_UNKNOWN_c1	= 0xc1,
	M1_PMU_PERFCTR_UNKNOWN_c4	= 0xc4,
	M1_PMU_PERFCTR_UNKNOWN_c5	= 0xc5,
	M1_PMU_PERFCTR_UNKNOWN_c6	= 0xc6,
	M1_PMU_PERFCTR_UNKNOWN_c8	= 0xc8,
	M1_PMU_PERFCTR_UNKNOWN_ca	= 0xca,
	M1_PMU_PERFCTR_UNKNOWN_cb	= 0xcb,
	M1_PMU_PERFCTR_UNKNOWN_f5	= 0xf5,
	M1_PMU_PERFCTR_UNKNOWN_f6	= 0xf6,
	M1_PMU_PERFCTR_UNKNOWN_f7	= 0xf7,
	M1_PMU_PERFCTR_UNKNOWN_f8	= 0xf8,
	M1_PMU_PERFCTR_UNKNOWN_fd	= 0xfd,
	M1_PMU_PERFCTR_LAST		= M1_PMU_CFG_EVENT,

	/*
	 * From this point onwards, these are not actual HW events,
	 * but attributes that get stored in hw->config_base.
	 */
	M1_PMU_CFG_COUNT_USER		= BIT(8),
	M1_PMU_CFG_COUNT_KERNEL		= BIT(9),
};

/*
 * Per-event affinity table. Most events can be installed on counter
 * 2-9, but there are a number of exceptions. Note that this table
 * has been created experimentally, and I wouldn't be surprised if more
 * counters had strange affinities.
 */
static const u16 m1_pmu_event_affinity[M1_PMU_PERFCTR_LAST + 1] = {
	[0 ... M1_PMU_PERFCTR_LAST]	= ANY_BUT_0_1,
	[M1_PMU_PERFCTR_UNKNOWN_01]	= BIT(7),
	[M1_PMU_PERFCTR_CPU_CYCLES]	= ANY_BUT_0_1 | BIT(0),
	[M1_PMU_PERFCTR_INSTRUCTIONS]	= BIT(7) | BIT(1),
	[M1_PMU_PERFCTR_UNKNOWN_8d]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_8e]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_8f]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_90]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_93]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_94]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_95]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_96]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_97]	= BIT(7),
	[M1_PMU_PERFCTR_UNKNOWN_98]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_99]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_9a]	= BIT(7),
	[M1_PMU_PERFCTR_UNKNOWN_9b]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_9c]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_9f]	= BIT(7),
	[M1_PMU_PERFCTR_UNKNOWN_bf]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_c0]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_c1]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_c4]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_c5]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_c6]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_c8]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_ca]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_cb]	= ONLY_5_6_7,
	[M1_PMU_PERFCTR_UNKNOWN_f5]	= ONLY_2_4_6,
	[M1_PMU_PERFCTR_UNKNOWN_f6]	= ONLY_2_4_6,
	[M1_PMU_PERFCTR_UNKNOWN_f7]	= ONLY_2_4_6,
	[M1_PMU_PERFCTR_UNKNOWN_f8]	= ONLY_2_TO_7,
	[M1_PMU_PERFCTR_UNKNOWN_fd]	= ONLY_2_4_6,
};

static const unsigned m1_pmu_perf_map[PERF_COUNT_HW_MAX] = {
	PERF_MAP_ALL_UNSUPPORTED,
	[PERF_COUNT_HW_CPU_CYCLES]	= M1_PMU_PERFCTR_CPU_CYCLES,
	[PERF_COUNT_HW_INSTRUCTIONS]	= M1_PMU_PERFCTR_INSTRUCTIONS,
	/* No idea about the rest yet */
};

/* sysfs definitions */
static ssize_t m1_pmu_events_sysfs_show(struct device *dev,
					struct device_attribute *attr,
					char *page)
{
	struct perf_pmu_events_attr *pmu_attr;

	pmu_attr = container_of(attr, struct perf_pmu_events_attr, attr);

	return sprintf(page, "event=0x%04llx\n", pmu_attr->id);
}

#define M1_PMU_EVENT_ATTR(name, config)					\
	PMU_EVENT_ATTR_ID(name, m1_pmu_events_sysfs_show, config)

static struct attribute *m1_pmu_event_attrs[] = {
	M1_PMU_EVENT_ATTR(cycles, M1_PMU_PERFCTR_CPU_CYCLES),
	M1_PMU_EVENT_ATTR(instructions, M1_PMU_PERFCTR_INSTRUCTIONS),
	NULL,
};

static const struct attribute_group m1_pmu_events_attr_group = {
	.name = "events",
	.attrs = m1_pmu_event_attrs,
};

PMU_FORMAT_ATTR(event, "config:0-7");

static struct attribute *m1_pmu_format_attrs[] = {
	&format_attr_event.attr,
	NULL,
};

static const struct attribute_group m1_pmu_format_attr_group = {
	.name = "format",
	.attrs = m1_pmu_format_attrs,
};

/* Low level accessors. No synchronisation. */
#define PMU_READ_COUNTER(_idx)						\
	case _idx:	return read_sysreg_s(SYS_IMP_APL_PMC## _idx ##_EL1)

#define PMU_WRITE_COUNTER(_val, _idx)					\
	case _idx:							\
		write_sysreg_s(_val, SYS_IMP_APL_PMC## _idx ##_EL1);	\
		return

static u64 m1_pmu_read_hw_counter(unsigned int index)
{
	switch (index) {
		PMU_READ_COUNTER(0);
		PMU_READ_COUNTER(1);
		PMU_READ_COUNTER(2);
		PMU_READ_COUNTER(3);
		PMU_READ_COUNTER(4);
		PMU_READ_COUNTER(5);
		PMU_READ_COUNTER(6);
		PMU_READ_COUNTER(7);
		PMU_READ_COUNTER(8);
		PMU_READ_COUNTER(9);
	}

	BUG();
}

static void m1_pmu_write_hw_counter(u64 val, unsigned int index)
{
	switch (index) {
		PMU_WRITE_COUNTER(val, 0);
		PMU_WRITE_COUNTER(val, 1);
		PMU_WRITE_COUNTER(val, 2);
		PMU_WRITE_COUNTER(val, 3);
		PMU_WRITE_COUNTER(val, 4);
		PMU_WRITE_COUNTER(val, 5);
		PMU_WRITE_COUNTER(val, 6);
		PMU_WRITE_COUNTER(val, 7);
		PMU_WRITE_COUNTER(val, 8);
		PMU_WRITE_COUNTER(val, 9);
	}

	BUG();
}

#define get_bit_offset(index, mask)	(__ffs(mask) + (index))

static void __m1_pmu_enable_counter(unsigned int index, bool en)
{
	u64 val, bit;

	switch (index) {
	case 0 ... 7:
		bit = BIT(get_bit_offset(index, PMCR0_CNT_ENABLE_0_7));
		break;
	case 8 ... 9:
		bit = BIT(get_bit_offset(index - 8, PMCR0_CNT_ENABLE_8_9));
		break;
	default:
		BUG();
	}

	val = read_sysreg_s(SYS_IMP_APL_PMCR0_EL1);

	if (en)
		val |= bit;
	else
		val &= ~bit;

	write_sysreg_s(val, SYS_IMP_APL_PMCR0_EL1);
}

static void m1_pmu_enable_counter(unsigned int index)
{
	__m1_pmu_enable_counter(index, true);
}

static void m1_pmu_disable_counter(unsigned int index)
{
	__m1_pmu_enable_counter(index, false);
}

static void __m1_pmu_enable_counter_interrupt(unsigned int index, bool en)
{
	u64 val, bit;

	switch (index) {
	case 0 ... 7:
		bit = BIT(get_bit_offset(index, PMCR0_PMI_ENABLE_0_7));
		break;
	case 8 ... 9:
		bit = BIT(get_bit_offset(index - 8, PMCR0_PMI_ENABLE_8_9));
		break;
	default:
		BUG();
	}

	val = read_sysreg_s(SYS_IMP_APL_PMCR0_EL1);

	if (en)
		val |= bit;
	else
		val &= ~bit;

	write_sysreg_s(val, SYS_IMP_APL_PMCR0_EL1);
}

static void m1_pmu_enable_counter_interrupt(unsigned int index)
{
	__m1_pmu_enable_counter_interrupt(index, true);
}

static void m1_pmu_disable_counter_interrupt(unsigned int index)
{
	__m1_pmu_enable_counter_interrupt(index, false);
}

static void m1_pmu_configure_counter(unsigned int index, u8 event,
				     bool user, bool kernel)
{
	u64 val, user_bit, kernel_bit;
	int shift;

	switch (index) {
	case 0 ... 7:
		user_bit = BIT(get_bit_offset(index, PMCR1_COUNT_A64_EL0_0_7));
		kernel_bit = BIT(get_bit_offset(index, PMCR1_COUNT_A64_EL1_0_7));
		break;
	case 8 ... 9:
		user_bit = BIT(get_bit_offset(index - 8, PMCR1_COUNT_A64_EL0_8_9));
		kernel_bit = BIT(get_bit_offset(index - 8, PMCR1_COUNT_A64_EL1_8_9));
		break;
	default:
		BUG();
	}

	val = read_sysreg_s(SYS_IMP_APL_PMCR1_EL1);

	if (user)
		val |= user_bit;
	else
		val &= ~user_bit;

	if (kernel)
		val |= kernel_bit;
	else
		val &= ~kernel_bit;

	write_sysreg_s(val, SYS_IMP_APL_PMCR1_EL1);

	/*
	 * Counters 0 and 1 have fixed events. For anything else,
	 * place the event at the expected location in the relevant
	 * register (PMESR0 holds the event configuration for counters
	 * 2-5, resp. PMESR1 for counters 6-9).
	 */
	switch (index) {
	case 0 ... 1:
		break;
	case 2 ... 5:
		shift = (index - 2) * 8;
		val = read_sysreg_s(SYS_IMP_APL_PMESR0_EL1);
		val &= ~((u64)0xff << shift);
		val |= (u64)event << shift;
		write_sysreg_s(val, SYS_IMP_APL_PMESR0_EL1);
		break;
	case 6 ... 9:
		shift = (index - 6) * 8;
		val = read_sysreg_s(SYS_IMP_APL_PMESR1_EL1);
		val &= ~((u64)0xff << shift);
		val |= (u64)event << shift;
		write_sysreg_s(val, SYS_IMP_APL_PMESR1_EL1);
		break;
	}
}

/* arm_pmu backend */
static void m1_pmu_enable_event(struct perf_event *event)
{
	bool user, kernel;
	u8 evt;

	evt = event->hw.config_base & M1_PMU_CFG_EVENT;
	user = event->hw.config_base & M1_PMU_CFG_COUNT_USER;
	kernel = event->hw.config_base & M1_PMU_CFG_COUNT_KERNEL;

	m1_pmu_disable_counter_interrupt(event->hw.idx);
	m1_pmu_disable_counter(event->hw.idx);
	isb();

	m1_pmu_configure_counter(event->hw.idx, evt, user, kernel);
	m1_pmu_enable_counter(event->hw.idx);
	m1_pmu_enable_counter_interrupt(event->hw.idx);
	isb();
}

static void m1_pmu_disable_event(struct perf_event *event)
{
	m1_pmu_disable_counter_interrupt(event->hw.idx);
	m1_pmu_disable_counter(event->hw.idx);
	isb();
}

static irqreturn_t m1_pmu_handle_irq(struct arm_pmu *cpu_pmu)
{
	struct pmu_hw_events *cpuc = this_cpu_ptr(cpu_pmu->hw_events);
	struct pt_regs *regs;
	u64 overflow, state;
	int idx;

	overflow = read_sysreg_s(SYS_IMP_APL_PMSR_EL1);
	if (!overflow) {
		/* Spurious interrupt? */
		state = read_sysreg_s(SYS_IMP_APL_PMCR0_EL1);
		state &= ~PMCR0_IACT;
		write_sysreg_s(state, SYS_IMP_APL_PMCR0_EL1);
		isb();
		return IRQ_NONE;
	}

	cpu_pmu->stop(cpu_pmu);

	regs = get_irq_regs();

	for (idx = 0; idx < cpu_pmu->num_events; idx++) {
		struct perf_event *event = cpuc->events[idx];
		struct perf_sample_data data;

		if (!event)
			continue;

		armpmu_event_update(event);
		perf_sample_data_init(&data, 0, event->hw.last_period);
		if (!armpmu_event_set_period(event))
			continue;

		if (perf_event_overflow(event, &data, regs))
			m1_pmu_disable_event(event);
	}

	cpu_pmu->start(cpu_pmu);

	return IRQ_HANDLED;
}

static u64 m1_pmu_read_counter(struct perf_event *event)
{
	return m1_pmu_read_hw_counter(event->hw.idx);
}

static void m1_pmu_write_counter(struct perf_event *event, u64 value)
{
	m1_pmu_write_hw_counter(value, event->hw.idx);
	isb();
}

static int m1_pmu_get_event_idx(struct pmu_hw_events *cpuc,
				struct perf_event *event)
{
	unsigned long evtype = event->hw.config_base & M1_PMU_CFG_EVENT;
	unsigned long affinity = m1_pmu_event_affinity[evtype];
	int idx;

	/*
	 * Place the event on the first free counter that can count
	 * this event.
	 *
	 * We could do a better job if we had a view of all the events
	 * counting on the PMU at any given time, and by placing the
	 * most constraining events first.
	 */
	for_each_set_bit(idx, &affinity, M1_PMU_NR_COUNTERS) {
		if (!test_and_set_bit(idx, cpuc->used_mask))
			return idx;
	}

	return -EAGAIN;
}

static void m1_pmu_clear_event_idx(struct pmu_hw_events *cpuc,
				   struct perf_event *event)
{
	clear_bit(event->hw.idx, cpuc->used_mask);
}

static void __m1_pmu_set_mode(u8 mode)
{
	u64 val;

	val = read_sysreg_s(SYS_IMP_APL_PMCR0_EL1);
	val &= ~(PMCR0_IMODE | PMCR0_IACT);
	val |= FIELD_PREP(PMCR0_IMODE, mode);
	write_sysreg_s(val, SYS_IMP_APL_PMCR0_EL1);
	isb();
}

static void m1_pmu_start(struct arm_pmu *cpu_pmu)
{
	__m1_pmu_set_mode(PMCR0_IMODE_FIQ);
}

static void m1_pmu_stop(struct arm_pmu *cpu_pmu)
{
	__m1_pmu_set_mode(PMCR0_IMODE_OFF);
}

static int m1_pmu_map_event(struct perf_event *event)
{
	/*
	 * Although the counters are 48bit wide, bit 47 is what
	 * triggers the overflow interrupt. Advertise the counters
	 * being 47bit wide to mimick the behaviour of the ARM PMU.
	 */
	event->hw.flags |= ARMPMU_EVT_47BIT;
	return armpmu_map_event(event, &m1_pmu_perf_map, NULL, M1_PMU_CFG_EVENT);
}

static void m1_pmu_reset(void *info)
{
	int i;

	__m1_pmu_set_mode(PMCR0_IMODE_OFF);

	for (i = 0; i < M1_PMU_NR_COUNTERS; i++) {
		m1_pmu_disable_counter(i);
		m1_pmu_disable_counter_interrupt(i);
		m1_pmu_write_hw_counter(0, i);
	}

	isb();
}

static int m1_pmu_set_event_filter(struct hw_perf_event *event,
				   struct perf_event_attr *attr)
{
	unsigned long config_base = 0;

	if (!attr->exclude_guest)
		return -EINVAL;
	if (!attr->exclude_kernel)
		config_base |= M1_PMU_CFG_COUNT_KERNEL;
	if (!attr->exclude_user)
		config_base |= M1_PMU_CFG_COUNT_USER;

	event->config_base = config_base;

	return 0;
}

static int m1_pmu_init(struct arm_pmu *cpu_pmu)
{
	cpu_pmu->handle_irq	  = m1_pmu_handle_irq;
	cpu_pmu->enable		  = m1_pmu_enable_event;
	cpu_pmu->disable	  = m1_pmu_disable_event;
	cpu_pmu->read_counter	  = m1_pmu_read_counter;
	cpu_pmu->write_counter	  = m1_pmu_write_counter;
	cpu_pmu->get_event_idx	  = m1_pmu_get_event_idx;
	cpu_pmu->clear_event_idx  = m1_pmu_clear_event_idx;
	cpu_pmu->start		  = m1_pmu_start;
	cpu_pmu->stop		  = m1_pmu_stop;
	cpu_pmu->map_event	  = m1_pmu_map_event;
	cpu_pmu->reset		  = m1_pmu_reset;
	cpu_pmu->set_event_filter = m1_pmu_set_event_filter;

	cpu_pmu->num_events	  = M1_PMU_NR_COUNTERS;
	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_EVENTS] = &m1_pmu_events_attr_group;
	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_FORMATS] = &m1_pmu_format_attr_group;
	return 0;
}

/* Device driver gunk */
static int m1_pmu_ice_init(struct arm_pmu *cpu_pmu)
{
	cpu_pmu->name = "apple_icestorm_pmu";
	return m1_pmu_init(cpu_pmu);
}

static int m1_pmu_fire_init(struct arm_pmu *cpu_pmu)
{
	cpu_pmu->name = "apple_firestorm_pmu";
	return m1_pmu_init(cpu_pmu);
}

static const struct of_device_id m1_pmu_of_device_ids[] = {
	{ .compatible = "apple,icestorm-pmu",	.data = m1_pmu_ice_init, },
	{ .compatible = "apple,firestorm-pmu",	.data = m1_pmu_fire_init, },
	{ },
};
MODULE_DEVICE_TABLE(of, m1_pmu_of_device_ids);

static int m1_pmu_device_probe(struct platform_device *pdev)
{
	return arm_pmu_device_probe(pdev, m1_pmu_of_device_ids, NULL);
}

static struct platform_driver m1_pmu_driver = {
	.driver		= {
		.name			= "apple-m1-cpu-pmu",
		.of_match_table		= m1_pmu_of_device_ids,
		.suppress_bind_attrs	= true,
	},
	.probe		= m1_pmu_device_probe,
};

module_platform_driver(m1_pmu_driver);
MODULE_LICENSE("GPL v2");