[v5,1/3] perf: starfive: Add StarLink PMU support

diff --git a/drivers/perf/Kconfig b/drivers/perf/Kconfig
index 273d67ecf6d2..41278742ef88 100644
--- a/drivers/perf/Kconfig
+++ b/drivers/perf/Kconfig
@@ -86,6 +86,15 @@  config RISCV_PMU_SBI
 	  full perf feature support i.e. counter overflow, privilege mode
 	  filtering, counter configuration.
 
+config STARFIVE_STARLINK_PMU
+	depends on ARCH_STARFIVE
+	bool "StarFive StarLink PMU"
+	help
+	   Provide support for StarLink Performance Monitor Unit.
+	   StarLink Performance Monitor Unit integrates one or more cores with
+	   an L3 memory system. The L3 cache events are added into perf event
+	   subsystem, allowing monitoring of various L3 cache perf events.
+
 config ARM_PMU_ACPI
 	depends on ARM_PMU && ACPI
 	def_bool y
diff --git a/drivers/perf/Makefile b/drivers/perf/Makefile
index 16b3ec4db916..e2153aee1e04 100644
--- a/drivers/perf/Makefile
+++ b/drivers/perf/Makefile
@@ -15,6 +15,7 @@  obj-$(CONFIG_QCOM_L3_PMU) += qcom_l3_pmu.o
 obj-$(CONFIG_RISCV_PMU) += riscv_pmu.o
 obj-$(CONFIG_RISCV_PMU_LEGACY) += riscv_pmu_legacy.o
 obj-$(CONFIG_RISCV_PMU_SBI) += riscv_pmu_sbi.o
+obj-$(CONFIG_STARFIVE_STARLINK_PMU) += starfive_starlink_pmu.o
 obj-$(CONFIG_THUNDERX2_PMU) += thunderx2_pmu.o
 obj-$(CONFIG_XGENE_PMU) += xgene_pmu.o
 obj-$(CONFIG_ARM_SPE_PMU) += arm_spe_pmu.o
diff --git a/drivers/perf/starfive_starlink_pmu.c b/drivers/perf/starfive_starlink_pmu.c
new file mode 100644
index 000000000000..2447ca09a471
--- /dev/null
+++ b/drivers/perf/starfive_starlink_pmu.c
@@ -0,0 +1,643 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * StarFive's StarLink PMU driver
+ *
+ * Copyright (C) 2023 StarFive Technology Co., Ltd.
+ *
+ * Author: Ji Sheng Teoh <jisheng.teoh@starfivetech.com>
+ *
+ */
+
+#define STARLINK_PMU_PDEV_NAME	"starfive_starlink_pmu"
+#define pr_fmt(fmt)	STARLINK_PMU_PDEV_NAME ": " fmt
+
+#include <linux/bitmap.h>
+#include <linux/cpu_pm.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/perf_event.h>
+#include <linux/platform_device.h>
+#include <linux/sysfs.h>
+
+#define STARLINK_PMU_MAX_COUNTERS			64
+#define STARLINK_PMU_NUM_COUNTERS			16
+#define STARLINK_PMU_IDX_CYCLE_COUNTER			63
+
+#define STARLINK_PMU_EVENT_SELECT			0x060
+#define STARLINK_PMU_EVENT_COUNTER			0x160
+#define STARLINK_PMU_COUNTER_MASK			GENMASK_ULL(63, 0)
+#define STARLINK_PMU_CYCLE_COUNTER			0x058
+
+#define STARLINK_PMU_CONTROL				0x040
+#define STARLINK_PMU_GLOBAL_ENABLE			BIT(0)
+
+#define STARLINK_PMU_INTERRUPT_ENABLE			0x050
+#define STARLINK_PMU_COUNTER_OVERFLOW_STATUS		0x048
+#define STARLINK_PMU_CYCLE_OVERFLOW_MASK		BIT(63)
+
+#define STARLINK_CYCLES				0x058
+#define CACHE_READ_REQUEST			0x04000701
+#define CACHE_WRITE_REQUEST			0x03000001
+#define CACHE_RELEASE_REQUEST			0x0003e001
+#define CACHE_READ_HIT				0x00901202
+#define CACHE_READ_MISS				0x04008002
+#define CACHE_WRITE_HIT				0x006c0002
+#define CACHE_WRITE_MISS			0x03000002
+#define CACHE_WRITEBACK				0x00000403
+
+#define to_starlink_pmu(p) (container_of(p, struct starlink_pmu, pmu))
+
+#define STARLINK_FORMAT_ATTR(_name, _config)				      \
+	(&((struct dev_ext_attribute[]) {				      \
+		{ .attr = __ATTR(_name, 0444, starlink_pmu_sysfs_format_show, NULL), \
+		  .var = (void *)_config, }				      \
+	})[0].attr.attr)
+
+#define STARLINK_EVENT_ATTR(_name, _id)					     \
+	PMU_EVENT_ATTR_ID(_name, starlink_pmu_sysfs_event_show, _id)
+
+static int starlink_pmu_cpuhp_state;
+
+struct starlink_hw_events {
+	struct perf_event	*events[STARLINK_PMU_MAX_COUNTERS];
+	DECLARE_BITMAP(used_mask, STARLINK_PMU_MAX_COUNTERS);
+};
+
+struct starlink_pmu {
+	struct pmu					pmu;
+	struct starlink_hw_events			__percpu *hw_events;
+	struct hlist_node				node;
+	struct notifier_block				starlink_pmu_pm_nb;
+	void __iomem					*pmu_base;
+	cpumask_t					cpumask;
+	int						irq;
+};
+
+static ssize_t
+starlink_pmu_sysfs_format_show(struct device *dev,
+			       struct device_attribute *attr,
+			       char *buf)
+{
+	struct dev_ext_attribute *eattr = container_of(attr,
+						       struct dev_ext_attribute, attr);
+
+	return sysfs_emit(buf, "%s\n", (char *)eattr->var);
+}
+
+static struct attribute *starlink_pmu_format_attrs[] = {
+	STARLINK_FORMAT_ATTR(event, "config:0-31"),
+	NULL
+};
+
+static const struct attribute_group starlink_pmu_format_attr_group = {
+	.name = "format",
+	.attrs = starlink_pmu_format_attrs,
+};
+
+static ssize_t
+starlink_pmu_sysfs_event_show(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+	struct perf_pmu_events_attr *eattr = container_of(attr,
+							  struct perf_pmu_events_attr, attr);
+
+	return sysfs_emit(buf, "event=0x%02llx\n", eattr->id);
+}
+
+static struct attribute *starlink_pmu_event_attrs[] = {
+	STARLINK_EVENT_ATTR(cycles, STARLINK_CYCLES),
+	STARLINK_EVENT_ATTR(read_request, CACHE_READ_REQUEST),
+	STARLINK_EVENT_ATTR(write_request, CACHE_WRITE_REQUEST),
+	STARLINK_EVENT_ATTR(release_request, CACHE_RELEASE_REQUEST),
+	STARLINK_EVENT_ATTR(read_hit, CACHE_READ_HIT),
+	STARLINK_EVENT_ATTR(read_miss, CACHE_READ_MISS),
+	STARLINK_EVENT_ATTR(write_hit, CACHE_WRITE_HIT),
+	STARLINK_EVENT_ATTR(write_miss, CACHE_WRITE_MISS),
+	STARLINK_EVENT_ATTR(writeback, CACHE_WRITEBACK),
+	NULL
+};
+
+static const struct attribute_group starlink_pmu_events_attr_group = {
+	.name = "events",
+	.attrs = starlink_pmu_event_attrs,
+};
+
+static ssize_t
+cpumask_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct starlink_pmu *starlink_pmu = to_starlink_pmu(dev_get_drvdata(dev));
+
+	return cpumap_print_to_pagebuf(true, buf, &starlink_pmu->cpumask);
+}
+
+static DEVICE_ATTR_RO(cpumask);
+
+static struct attribute *starlink_pmu_cpumask_attrs[] = {
+	&dev_attr_cpumask.attr,
+	NULL
+};
+
+static const struct attribute_group starlink_pmu_cpumask_attr_group = {
+	.attrs = starlink_pmu_cpumask_attrs,
+};
+
+static const struct attribute_group *starlink_pmu_attr_groups[] = {
+	&starlink_pmu_format_attr_group,
+	&starlink_pmu_events_attr_group,
+	&starlink_pmu_cpumask_attr_group,
+	NULL
+};
+
+static void starlink_pmu_set_event_period(struct perf_event *event)
+{
+	struct starlink_pmu *starlink_pmu = to_starlink_pmu(event->pmu);
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = event->hw.idx;
+
+	/*
+	 * Program counter to half of it's max count to handle
+	 * cases of extreme interrupt latency.
+	 */
+	u64 val = STARLINK_PMU_COUNTER_MASK >> 1;
+
+	local64_set(&hwc->prev_count, val);
+	if (hwc->config == STARLINK_CYCLES)
+		writeq(val, starlink_pmu->pmu_base + STARLINK_PMU_CYCLE_COUNTER);
+	else
+		writeq(val, starlink_pmu->pmu_base + STARLINK_PMU_EVENT_COUNTER +
+		       idx * sizeof(u64));
+}
+
+static void starlink_pmu_counter_start(struct perf_event *event,
+				       struct starlink_pmu *starlink_pmu)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = event->hw.idx;
+	u64 val;
+
+	/*
+	 * Enable counter overflow interrupt[63:0],
+	 * which is mapped as follow:
+	 *
+	 * event counter 0	- Bit [0]
+	 * event counter 1	- Bit [1]
+	 * ...
+	 * cycle counter	- Bit [63]
+	 */
+	val = readq(starlink_pmu->pmu_base + STARLINK_PMU_INTERRUPT_ENABLE);
+
+	if (hwc->config == STARLINK_CYCLES) {
+		/*
+		 * Cycle count has its dedicated register, and it starts
+		 * counting as soon as STARLINK_PMU_GLOBAL_ENABLE is set.
+		 */
+		val |= STARLINK_PMU_CYCLE_OVERFLOW_MASK;
+	} else {
+		writeq(event->hw.config, starlink_pmu->pmu_base +
+		       STARLINK_PMU_EVENT_SELECT + idx * sizeof(u64));
+
+		val |= (1 << idx);
+	}
+
+	writeq(val, starlink_pmu->pmu_base + STARLINK_PMU_INTERRUPT_ENABLE);
+
+	writeq(STARLINK_PMU_GLOBAL_ENABLE, starlink_pmu->pmu_base +
+	       STARLINK_PMU_CONTROL);
+}
+
+static void starlink_pmu_counter_stop(struct perf_event *event,
+				      struct starlink_pmu *starlink_pmu)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = event->hw.idx;
+	u64 val;
+
+	val = readq(starlink_pmu->pmu_base + STARLINK_PMU_CONTROL);
+	val &= ~STARLINK_PMU_GLOBAL_ENABLE;
+	writeq(val, starlink_pmu->pmu_base + STARLINK_PMU_CONTROL);
+
+	val = readq(starlink_pmu->pmu_base + STARLINK_PMU_INTERRUPT_ENABLE);
+	if (hwc->config == STARLINK_CYCLES)
+		val &= ~STARLINK_PMU_CYCLE_OVERFLOW_MASK;
+	else
+		val &= ~(1 << idx);
+
+	writeq(val, starlink_pmu->pmu_base + STARLINK_PMU_INTERRUPT_ENABLE);
+}
+
+static void starlink_pmu_update(struct perf_event *event)
+{
+	struct starlink_pmu *starlink_pmu = to_starlink_pmu(event->pmu);
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+	u64 prev_raw_count, new_raw_count;
+	u64 oldval;
+	u64 delta;
+
+	do {
+		prev_raw_count = local64_read(&hwc->prev_count);
+		if (hwc->config == STARLINK_CYCLES)
+			new_raw_count = readq(starlink_pmu->pmu_base +
+					      STARLINK_PMU_CYCLE_COUNTER);
+		else
+			new_raw_count = readq(starlink_pmu->pmu_base +
+					      STARLINK_PMU_EVENT_COUNTER +
+					      idx * sizeof(u64));
+		oldval = local64_cmpxchg(&hwc->prev_count, prev_raw_count,
+					 new_raw_count);
+	} while (oldval != prev_raw_count);
+
+	delta = (new_raw_count - prev_raw_count) & STARLINK_PMU_COUNTER_MASK;
+	local64_add(delta, &event->count);
+}
+
+static void starlink_pmu_start(struct perf_event *event, int flags)
+{
+	struct starlink_pmu *starlink_pmu = to_starlink_pmu(event->pmu);
+	struct hw_perf_event *hwc = &event->hw;
+
+	if (WARN_ON_ONCE(!(hwc->state & PERF_HES_STOPPED)))
+		return;
+
+	if (flags & PERF_EF_RELOAD)
+		WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
+
+	hwc->state = 0;
+
+	starlink_pmu_set_event_period(event);
+	starlink_pmu_counter_start(event, starlink_pmu);
+
+	perf_event_update_userpage(event);
+}
+
+static void starlink_pmu_stop(struct perf_event *event, int flags)
+{
+	struct starlink_pmu *starlink_pmu = to_starlink_pmu(event->pmu);
+	struct hw_perf_event *hwc = &event->hw;
+
+	if (hwc->state & PERF_HES_STOPPED)
+		return;
+
+	starlink_pmu_counter_stop(event, starlink_pmu);
+	starlink_pmu_update(event);
+	hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
+}
+
+static int starlink_pmu_add(struct perf_event *event, int flags)
+{
+	struct starlink_pmu *starlink_pmu = to_starlink_pmu(event->pmu);
+	struct starlink_hw_events *hw_events =
+					this_cpu_ptr(starlink_pmu->hw_events);
+	struct hw_perf_event *hwc = &event->hw;
+	unsigned long *used_mask = hw_events->used_mask;
+	u32 n_events = STARLINK_PMU_NUM_COUNTERS;
+	int idx;
+
+	/*
+	 * Cycle counter has dedicated register to hold counter value.
+	 * Event other than cycle count has to be enabled through
+	 * event select register, and assigned with independent counter
+	 * as they appear.
+	 */
+
+	if (hwc->config == STARLINK_CYCLES) {
+		idx = STARLINK_PMU_IDX_CYCLE_COUNTER;
+	} else {
+		idx = find_first_zero_bit(used_mask, n_events);
+		/* All counter are in use */
+		if (idx < 0)
+			return idx;
+
+		set_bit(idx, used_mask);
+	}
+
+	hwc->idx = idx;
+	hw_events->events[idx] = event;
+	hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
+
+	if (flags & PERF_EF_START)
+		starlink_pmu_start(event, PERF_EF_RELOAD);
+
+	perf_event_update_userpage(event);
+
+	return 0;
+}
+
+static void starlink_pmu_del(struct perf_event *event, int flags)
+{
+	struct starlink_pmu *starlink_pmu = to_starlink_pmu(event->pmu);
+	struct starlink_hw_events *hw_events =
+					this_cpu_ptr(starlink_pmu->hw_events);
+	struct hw_perf_event *hwc = &event->hw;
+
+	starlink_pmu_stop(event, PERF_EF_UPDATE);
+	hw_events->events[hwc->idx] = NULL;
+	clear_bit(hwc->idx, hw_events->used_mask);
+
+	perf_event_update_userpage(event);
+}
+
+static bool starlink_pmu_validate_event_group(struct perf_event *event)
+{
+	struct perf_event *leader = event->group_leader;
+	struct perf_event *sibling;
+	int counter = 1;
+
+	/*
+	 * Ensure hardware events in the group are on the same PMU,
+	 * software events are acceptable.
+	 */
+	if (event->group_leader->pmu != event->pmu &&
+	    !is_software_event(event->group_leader))
+		return false;
+
+	for_each_sibling_event(sibling, leader) {
+		if (sibling->pmu != event->pmu && !is_software_event(sibling))
+			return false;
+
+		counter++;
+	}
+
+	return counter <= STARLINK_PMU_NUM_COUNTERS;
+}
+
+static int starlink_pmu_event_init(struct perf_event *event)
+{
+	struct starlink_pmu *starlink_pmu = to_starlink_pmu(event->pmu);
+	struct hw_perf_event *hwc = &event->hw;
+
+	/*
+	 * Sampling is not supported, as counters are shared
+	 * by all CPU.
+	 */
+	if (hwc->sample_period)
+		return -EOPNOTSUPP;
+
+	/*
+	 * Per-task and attach to a task are not supported,
+	 * as uncore events are not specific to any CPU.
+	 */
+	if (event->cpu < 0 || event->attach_state & PERF_ATTACH_TASK)
+		return -EOPNOTSUPP;
+
+	if (!starlink_pmu_validate_event_group(event))
+		return -EINVAL;
+
+	hwc->idx = -1;
+	hwc->config = event->attr.config;
+	event->cpu = cpumask_first(&starlink_pmu->cpumask);
+
+	return 0;
+}
+
+static irqreturn_t starlink_pmu_handle_irq(int irq_num, void *data)
+{
+	struct starlink_pmu *starlink_pmu = data;
+	struct starlink_hw_events *hw_events =
+			this_cpu_ptr(starlink_pmu->hw_events);
+	bool handled = false;
+	int idx;
+	u64 overflow_status;
+
+	for (idx = 0; idx < STARLINK_PMU_MAX_COUNTERS; idx++) {
+		struct perf_event *event = hw_events->events[idx];
+
+		if (!event)
+			continue;
+
+		overflow_status = readq(starlink_pmu->pmu_base +
+					STARLINK_PMU_COUNTER_OVERFLOW_STATUS);
+		if (!(overflow_status & BIT(idx)))
+			continue;
+
+		writeq(1 << idx, starlink_pmu->pmu_base +
+		       STARLINK_PMU_COUNTER_OVERFLOW_STATUS);
+
+		starlink_pmu_update(event);
+		starlink_pmu_set_event_period(event);
+		handled = true;
+	}
+	return IRQ_RETVAL(handled);
+}
+
+static int starlink_setup_irqs(struct starlink_pmu *starlink_pmu,
+			       struct platform_device *pdev)
+{
+	int ret, irq;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return -EINVAL;
+
+	ret = devm_request_irq(&pdev->dev, irq, starlink_pmu_handle_irq,
+			       0, STARLINK_PMU_PDEV_NAME, starlink_pmu);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret, "Failed to request IRQ\n");
+
+	starlink_pmu->irq = irq;
+
+	return 0;
+}
+
+static int starlink_pmu_pm_notify(struct notifier_block *b,
+				  unsigned long cmd, void *v)
+{
+	struct starlink_pmu *starlink_pmu = container_of(b, struct starlink_pmu,
+							 starlink_pmu_pm_nb);
+	struct starlink_hw_events *hw_events =
+					this_cpu_ptr(starlink_pmu->hw_events);
+	int enabled = bitmap_weight(hw_events->used_mask,
+				    STARLINK_PMU_MAX_COUNTERS);
+	struct perf_event *event;
+	int idx;
+
+	if (!enabled)
+		return NOTIFY_OK;
+
+	for (idx = 0; idx < STARLINK_PMU_MAX_COUNTERS; idx++) {
+		event = hw_events->events[idx];
+		if (!event)
+			continue;
+
+		switch (cmd) {
+		case CPU_PM_ENTER:
+			/* Stop and update the counter */
+			starlink_pmu_stop(event, PERF_EF_UPDATE);
+			break;
+		case CPU_PM_EXIT:
+		case CPU_PM_ENTER_FAILED:
+			/* Restore and enable the counter */
+			starlink_pmu_start(event, PERF_EF_RELOAD);
+			break;
+		default:
+			break;
+		}
+	}
+
+	return NOTIFY_OK;
+}
+
+static int starlink_pmu_pm_register(struct starlink_pmu *starlink_pmu)
+{
+	if (!IS_ENABLED(CONFIG_CPU_PM))
+		return 0;
+
+	starlink_pmu->starlink_pmu_pm_nb.notifier_call = starlink_pmu_pm_notify;
+	return cpu_pm_register_notifier(&starlink_pmu->starlink_pmu_pm_nb);
+}
+
+static void starlink_pmu_pm_unregister(struct starlink_pmu *starlink_pmu)
+{
+	if (!IS_ENABLED(CONFIG_CPU_PM))
+		return;
+
+	cpu_pm_unregister_notifier(&starlink_pmu->starlink_pmu_pm_nb);
+}
+
+static void starlink_pmu_destroy(struct starlink_pmu *starlink_pmu)
+{
+	starlink_pmu_pm_unregister(starlink_pmu);
+	cpuhp_state_remove_instance(starlink_pmu_cpuhp_state,
+				    &starlink_pmu->node);
+}
+
+static int starlink_pmu_probe(struct platform_device *pdev)
+{
+	struct starlink_pmu *starlink_pmu;
+	struct starlink_hw_events *hw_events;
+	struct resource *res;
+	int cpuid, i, ret;
+
+	starlink_pmu = devm_kzalloc(&pdev->dev, sizeof(*starlink_pmu), GFP_KERNEL);
+	if (!starlink_pmu)
+		return -ENOMEM;
+
+	starlink_pmu->pmu_base =
+			devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(starlink_pmu->pmu_base))
+		return PTR_ERR(starlink_pmu->pmu_base);
+
+	starlink_pmu->hw_events = alloc_percpu_gfp(struct starlink_hw_events,
+						   GFP_KERNEL);
+	if (!starlink_pmu->hw_events) {
+		dev_err(&pdev->dev, "Failed to allocate per-cpu PMU data\n");
+		kfree(starlink_pmu);
+		return -ENOMEM;
+	}
+
+	for_each_possible_cpu(cpuid) {
+		hw_events = per_cpu_ptr(starlink_pmu->hw_events, cpuid);
+		for (i = 0; i < STARLINK_PMU_MAX_COUNTERS; i++)
+			hw_events->events[i] = NULL;
+	}
+
+	ret = starlink_setup_irqs(starlink_pmu, pdev);
+	if (ret)
+		return ret;
+
+	ret = cpuhp_state_add_instance(starlink_pmu_cpuhp_state,
+				       &starlink_pmu->node);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register hotplug\n");
+		return ret;
+	}
+
+	ret = starlink_pmu_pm_register(starlink_pmu);
+	if (ret) {
+		cpuhp_state_remove_instance(starlink_pmu_cpuhp_state,
+					    &starlink_pmu->node);
+		return ret;
+	}
+
+	starlink_pmu->pmu = (struct pmu) {
+		.task_ctx_nr	= perf_invalid_context,
+		.event_init	= starlink_pmu_event_init,
+		.add		= starlink_pmu_add,
+		.del		= starlink_pmu_del,
+		.start		= starlink_pmu_start,
+		.stop		= starlink_pmu_stop,
+		.read		= starlink_pmu_update,
+		.attr_groups	= starlink_pmu_attr_groups,
+	};
+
+	ret = perf_pmu_register(&starlink_pmu->pmu, STARLINK_PMU_PDEV_NAME, -1);
+	if (ret)
+		starlink_pmu_destroy(starlink_pmu);
+
+	return ret;
+}
+
+static const struct of_device_id starlink_pmu_of_match[] = {
+	{ .compatible = "starfive,jh8100-starlink-pmu" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, starlink_pmu_of_match);
+
+static struct platform_driver starlink_pmu_driver = {
+	.driver = {
+		.name	= STARLINK_PMU_PDEV_NAME,
+		.of_match_table = starlink_pmu_of_match,
+		.suppress_bind_attrs = true,
+	},
+	.probe = starlink_pmu_probe,
+};
+
+static int
+starlink_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
+{
+	struct starlink_pmu *starlink_pmu = hlist_entry_safe(node,
+							     struct starlink_pmu,
+							     node);
+
+	if (cpumask_empty(&starlink_pmu->cpumask))
+		cpumask_set_cpu(cpu, &starlink_pmu->cpumask);
+
+	WARN_ON(irq_set_affinity(starlink_pmu->irq, cpumask_of(cpu)));
+
+	return 0;
+}
+
+static int
+starlink_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
+{
+	struct starlink_pmu *starlink_pmu = hlist_entry_safe(node,
+							     struct starlink_pmu,
+							     node);
+	unsigned int target;
+
+	if (!cpumask_test_and_clear_cpu(cpu, &starlink_pmu->cpumask))
+		return 0;
+
+	target = cpumask_any_but(cpu_online_mask, cpu);
+	if (target >= nr_cpu_ids)
+		return 0;
+
+	perf_pmu_migrate_context(&starlink_pmu->pmu, cpu, target);
+
+	cpumask_set_cpu(target, &starlink_pmu->cpumask);
+	WARN_ON(irq_set_affinity(starlink_pmu->irq, cpumask_of(target)));
+
+	return 0;
+}
+
+static int __init starlink_pmu_init(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
+				      "soc/starfive/starlink_pmu:online",
+				      starlink_pmu_online_cpu,
+				      starlink_pmu_offline_cpu);
+	if (ret < 0)
+		return ret;
+
+	starlink_pmu_cpuhp_state = ret;
+
+	return platform_driver_register(&starlink_pmu_driver);
+}
+
+device_initcall(starlink_pmu_init);