perf: ARM DynamIQ Shared Unit PMU support

Add support for the Cluster PMU part of the ARM DynamIQ Shared Unit (DSU).
The DSU integrates one or more cores with an L3 memory system, control
logic, and external interfaces to form a multicore cluster. The PMU
allows counting the various events related to L3, SCU etc, along with
providing a cycle counter.

The PMU can be accessed via system registers, which are common
to the cores in the same cluster. The PMU registers follow the
semantics of the ARMv8 PMU, mostly, with the exception that
the counters record the cluster wide events.

This driver is mostly based on the ARMv8 and CCI PMU drivers.
The driver only supports ARM64 at the moment. It can be extended
to support ARM32 by providing register accessors like we do in
arch/arm64/include/arm_dsu_pmu.h.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 843 insertions, 0 deletions

diff --git a/drivers/perf/arm_dsu_pmu.c b/drivers/perf/arm_dsu_pmu.c
new file mode 100644
index 000000000000..37c0526c93d5
--- /dev/null
+++ b/drivers/perf/arm_dsu_pmu.c
@@ -0,0 +1,843 @@
+/*
+ * ARM DynamIQ Shared Unit (DSU) PMU driver
+ *
+ * Copyright (C) ARM Limited, 2017.
+ *
+ * Based on ARM CCI-PMU, ARMv8 PMU-v3 drivers.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#define PMUNAME		"arm_dsu"
+#define DRVNAME		PMUNAME "_pmu"
+#define pr_fmt(fmt)	DRVNAME ": " fmt
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/bug.h>
+#include <linux/cpumask.h>
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/perf_event.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include <asm/arm_dsu_pmu.h>
+#include <asm/local64.h>
+
+/* PMU event codes */
+#define DSU_PMU_EVT_CYCLES		0x11
+#define DSU_PMU_EVT_CHAIN		0x1e
+
+#define DSU_PMU_MAX_COMMON_EVENTS	0x40
+
+#define DSU_PMU_MAX_HW_CNTRS		32
+#define DSU_PMU_HW_COUNTER_MASK		(DSU_PMU_MAX_HW_CNTRS - 1)
+
+#define CLUSTERPMCR_E			BIT(0)
+#define CLUSTERPMCR_P			BIT(1)
+#define CLUSTERPMCR_C			BIT(2)
+#define CLUSTERPMCR_N_SHIFT		11
+#define CLUSTERPMCR_N_MASK		0x1f
+#define CLUSTERPMCR_IDCODE_SHIFT	16
+#define CLUSTERPMCR_IDCODE_MASK		0xff
+#define CLUSTERPMCR_IMP_SHIFT		24
+#define CLUSTERPMCR_IMP_MASK		0xff
+#define CLUSTERPMCR_RES_MASK		0x7e8
+#define CLUSTERPMCR_RES_VAL		0x40
+
+#define DSU_ACTIVE_CPU_MASK		0x0
+#define DSU_ASSOCIATED_CPU_MASK		0x1
+
+/*
+ * We use the index of the counters as they appear in the counter
+ * bit maps in the PMU registers (e.g CLUSTERPMSELR).
+ * i.e,
+ *	counter 0	- Bit 0
+ *	counter 1	- Bit 1
+ *	...
+ *	Cycle counter	- Bit 31
+ */
+#define DSU_PMU_IDX_CYCLE_COUNTER	31
+
+/* All event counters are 32bit, with a 64bit Cycle counter */
+#define DSU_PMU_COUNTER_WIDTH(idx)	\
+	(((idx) == DSU_PMU_IDX_CYCLE_COUNTER) ? 64 : 32)
+
+#define DSU_PMU_COUNTER_MASK(idx)	\
+	GENMASK_ULL((DSU_PMU_COUNTER_WIDTH((idx)) - 1), 0)
+
+#define DSU_EXT_ATTR(_name, _func, _config)		\
+	(&((struct dev_ext_attribute[]) {				\
+		{							\
+			.attr = __ATTR(_name, 0444, _func, NULL),	\
+			.var = (void *)_config				\
+		}							\
+	})[0].attr.attr)
+
+#define DSU_EVENT_ATTR(_name, _config)		\
+	DSU_EXT_ATTR(_name, dsu_pmu_sysfs_event_show, (unsigned long)_config)
+
+#define DSU_FORMAT_ATTR(_name, _config)		\
+	DSU_EXT_ATTR(_name, dsu_pmu_sysfs_format_show, (char *)_config)
+
+#define DSU_CPUMASK_ATTR(_name, _config)	\
+	DSU_EXT_ATTR(_name, dsu_pmu_cpumask_show, (unsigned long)_config)
+
+struct dsu_hw_events {
+	DECLARE_BITMAP(used_mask, DSU_PMU_MAX_HW_CNTRS);
+	struct perf_event	*events[DSU_PMU_MAX_HW_CNTRS];
+};
+
+/*
+ * struct dsu_pmu	- DSU PMU descriptor
+ *
+ * @pmu_lock		: Protects accesses to DSU PMU register from normal vs
+ *			  interrupt handler contexts.
+ * @hw_events		: Holds the event counter state.
+ * @associated_cpus	: CPUs attached to the DSU.
+ * @active_cpu		: CPU to which the PMU is bound for accesses.
+ * @cpuhp_node		: Node for CPU hotplug notifier link.
+ * @num_counters	: Number of event counters implemented by the PMU,
+ *			  excluding the cycle counter.
+ * @irq			: Interrupt line for counter overflow.
+ * @cpmceid_bitmap	: Bitmap for the availability of architected common
+ *			  events (event_code < 0x40).
+ */
+struct dsu_pmu {
+	struct pmu			pmu;
+	struct device			*dev;
+	raw_spinlock_t			pmu_lock;
+	struct dsu_hw_events		hw_events;
+	cpumask_t			associated_cpus;
+	cpumask_t			active_cpu;
+	struct hlist_node		cpuhp_node;
+	u8				num_counters;
+	int				irq;
+	DECLARE_BITMAP(cpmceid_bitmap, DSU_PMU_MAX_COMMON_EVENTS);
+};
+
+static unsigned long dsu_pmu_cpuhp_state;
+
+static inline struct dsu_pmu *to_dsu_pmu(struct pmu *pmu)
+{
+	return container_of(pmu, struct dsu_pmu, pmu);
+}
+
+static ssize_t dsu_pmu_sysfs_event_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct dev_ext_attribute *eattr = container_of(attr,
+					struct dev_ext_attribute, attr);
+	return snprintf(buf, PAGE_SIZE, "event=0x%lx\n",
+					 (unsigned long)eattr->var);
+}
+
+static ssize_t dsu_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 snprintf(buf, PAGE_SIZE, "%s\n", (char *)eattr->var);
+}
+
+static ssize_t dsu_pmu_cpumask_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	struct pmu *pmu = dev_get_drvdata(dev);
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(pmu);
+	struct dev_ext_attribute *eattr = container_of(attr,
+					struct dev_ext_attribute, attr);
+	unsigned long mask_id = (unsigned long)eattr->var;
+	const cpumask_t *cpumask;
+
+	switch (mask_id) {
+	case DSU_ACTIVE_CPU_MASK:
+		cpumask = &dsu_pmu->active_cpu;
+		break;
+	case DSU_ASSOCIATED_CPU_MASK:
+		cpumask = &dsu_pmu->associated_cpus;
+		break;
+	default:
+		return 0;
+	}
+	return cpumap_print_to_pagebuf(true, buf, cpumask);
+}
+
+static struct attribute *dsu_pmu_format_attrs[] = {
+	DSU_FORMAT_ATTR(event, "config:0-31"),
+	NULL,
+};
+
+static const struct attribute_group dsu_pmu_format_attr_group = {
+	.name = "format",
+	.attrs = dsu_pmu_format_attrs,
+};
+
+static struct attribute *dsu_pmu_event_attrs[] = {
+	DSU_EVENT_ATTR(cycles, 0x11),
+	DSU_EVENT_ATTR(bus_access, 0x19),
+	DSU_EVENT_ATTR(memory_error, 0x1a),
+	DSU_EVENT_ATTR(bus_cycles, 0x1d),
+	DSU_EVENT_ATTR(l3d_cache_allocate, 0x29),
+	DSU_EVENT_ATTR(l3d_cache_refill, 0x2a),
+	DSU_EVENT_ATTR(l3d_cache, 0x2b),
+	DSU_EVENT_ATTR(l3d_cache_wb, 0x2c),
+	NULL,
+};
+
+static umode_t
+dsu_pmu_event_attr_is_visible(struct kobject *kobj, struct attribute *attr,
+				int unused)
+{
+	struct pmu *pmu = dev_get_drvdata(kobj_to_dev(kobj));
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(pmu);
+	struct dev_ext_attribute *eattr = container_of(attr,
+					struct dev_ext_attribute, attr.attr);
+	unsigned long evt = (unsigned long)eattr->var;
+
+	return test_bit(evt, dsu_pmu->cpmceid_bitmap) ? attr->mode : 0;
+}
+
+static const struct attribute_group dsu_pmu_events_attr_group = {
+	.name = "events",
+	.attrs = dsu_pmu_event_attrs,
+	.is_visible = dsu_pmu_event_attr_is_visible,
+};
+
+static struct attribute *dsu_pmu_cpumask_attrs[] = {
+	DSU_CPUMASK_ATTR(cpumask, DSU_ACTIVE_CPU_MASK),
+	DSU_CPUMASK_ATTR(associated_cpus, DSU_ASSOCIATED_CPU_MASK),
+	NULL,
+};
+
+static const struct attribute_group dsu_pmu_cpumask_attr_group = {
+	.attrs = dsu_pmu_cpumask_attrs,
+};
+
+static const struct attribute_group *dsu_pmu_attr_groups[] = {
+	&dsu_pmu_cpumask_attr_group,
+	&dsu_pmu_events_attr_group,
+	&dsu_pmu_format_attr_group,
+	NULL,
+};
+
+static int dsu_pmu_get_online_cpu_any_but(struct dsu_pmu *dsu_pmu, int cpu)
+{
+	struct cpumask online_supported;
+
+	cpumask_and(&online_supported,
+			 &dsu_pmu->associated_cpus, cpu_online_mask);
+	return cpumask_any_but(&online_supported, cpu);
+}
+
+static inline bool dsu_pmu_counter_valid(struct dsu_pmu *dsu_pmu, u32 idx)
+{
+	return (idx < dsu_pmu->num_counters) ||
+	       (idx == DSU_PMU_IDX_CYCLE_COUNTER);
+}
+
+static inline u64 dsu_pmu_read_counter(struct perf_event *event)
+{
+	u64 val;
+	unsigned long flags;
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(event->pmu);
+	int idx = event->hw.idx;
+
+	if (WARN_ON(!cpumask_test_cpu(smp_processor_id(),
+				 &dsu_pmu->associated_cpus)))
+		return 0;
+
+	if (!dsu_pmu_counter_valid(dsu_pmu, idx)) {
+		dev_err(event->pmu->dev,
+			"Trying reading invalid counter %d\n", idx);
+		return 0;
+	}
+
+	raw_spin_lock_irqsave(&dsu_pmu->pmu_lock, flags);
+	if (idx == DSU_PMU_IDX_CYCLE_COUNTER)
+		val = __dsu_pmu_read_pmccntr();
+	else
+		val = __dsu_pmu_read_counter(idx);
+	raw_spin_unlock_irqrestore(&dsu_pmu->pmu_lock, flags);
+
+	return val;
+}
+
+static void dsu_pmu_write_counter(struct perf_event *event, u64 val)
+{
+	unsigned long flags;
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(event->pmu);
+	int idx = event->hw.idx;
+
+	if (WARN_ON(!cpumask_test_cpu(smp_processor_id(),
+			 &dsu_pmu->associated_cpus)))
+		return;
+
+	if (!dsu_pmu_counter_valid(dsu_pmu, idx)) {
+		dev_err(event->pmu->dev,
+			"writing to invalid counter %d\n", idx);
+		return;
+	}
+
+	raw_spin_lock_irqsave(&dsu_pmu->pmu_lock, flags);
+	if (idx == DSU_PMU_IDX_CYCLE_COUNTER)
+		__dsu_pmu_write_pmccntr(val);
+	else
+		__dsu_pmu_write_counter(idx, val);
+	raw_spin_unlock_irqrestore(&dsu_pmu->pmu_lock, flags);
+}
+
+static int dsu_pmu_get_event_idx(struct dsu_hw_events *hw_events,
+				 struct perf_event *event)
+{
+	int idx;
+	unsigned long evtype = event->attr.config;
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(event->pmu);
+	unsigned long *used_mask = hw_events->used_mask;
+
+	if (evtype == DSU_PMU_EVT_CYCLES) {
+		if (test_and_set_bit(DSU_PMU_IDX_CYCLE_COUNTER, used_mask))
+			return -EAGAIN;
+		return DSU_PMU_IDX_CYCLE_COUNTER;
+	}
+
+	idx = find_first_zero_bit(used_mask, dsu_pmu->num_counters);
+	if (idx >= dsu_pmu->num_counters)
+		return -EAGAIN;
+	set_bit(idx, hw_events->used_mask);
+	return idx;
+}
+
+static void dsu_pmu_enable_counter(struct dsu_pmu *dsu_pmu, int idx)
+{
+	__dsu_pmu_counter_interrupt_enable(idx);
+	__dsu_pmu_enable_counter(idx);
+}
+
+static void dsu_pmu_disable_counter(struct dsu_pmu *dsu_pmu, int idx)
+{
+	__dsu_pmu_disable_counter(idx);
+	__dsu_pmu_counter_interrupt_disable(idx);
+}
+
+static inline void dsu_pmu_set_event(struct dsu_pmu *dsu_pmu,
+					struct perf_event *event)
+{
+	int idx = event->hw.idx;
+	unsigned long flags;
+
+	if (!dsu_pmu_counter_valid(dsu_pmu, idx)) {
+		dev_err(event->pmu->dev,
+			"Trying to set invalid counter %d\n", idx);
+		return;
+	}
+
+	raw_spin_lock_irqsave(&dsu_pmu->pmu_lock, flags);
+	__dsu_pmu_set_event(idx, event->hw.config_base);
+	raw_spin_unlock_irqrestore(&dsu_pmu->pmu_lock, flags);
+}
+
+static void dsu_pmu_event_update(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	u64 delta, prev_count, new_count;
+
+	do {
+		/* We may also be called from the irq handler */
+		prev_count = local64_read(&hwc->prev_count);
+		new_count = dsu_pmu_read_counter(event);
+	} while (local64_cmpxchg(&hwc->prev_count, prev_count, new_count) !=
+			prev_count);
+	delta = (new_count - prev_count) & DSU_PMU_COUNTER_MASK(hwc->idx);
+	local64_add(delta, &event->count);
+}
+
+static void dsu_pmu_read(struct perf_event *event)
+{
+	dsu_pmu_event_update(event);
+}
+
+static inline u32 dsu_pmu_get_reset_overflow(void)
+{
+	return __dsu_pmu_get_reset_overflow();
+}
+
+/**
+ * dsu_pmu_set_event_period: Set the period for the counter.
+ *
+ * All DSU PMU event counters, except the cycle counter are 32bit
+ * counters. To handle cases of extreme interrupt latency, we program
+ * the counter with half of the max count for the counters.
+ */
+static void dsu_pmu_set_event_period(struct perf_event *event)
+{
+	int idx = event->hw.idx;
+	u64 val = DSU_PMU_COUNTER_MASK(idx) >> 1;
+
+	local64_set(&event->hw.prev_count, val);
+	dsu_pmu_write_counter(event, val);
+}
+
+static irqreturn_t dsu_pmu_handle_irq(int irq_num, void *dev)
+{
+	int i;
+	bool handled = false;
+	struct dsu_pmu *dsu_pmu = dev;
+	struct dsu_hw_events *hw_events = &dsu_pmu->hw_events;
+	unsigned long overflow;
+
+	overflow = dsu_pmu_get_reset_overflow();
+	if (!overflow)
+		return IRQ_NONE;
+
+	for_each_set_bit(i, &overflow, DSU_PMU_MAX_HW_CNTRS) {
+		struct perf_event *event = hw_events->events[i];
+
+		if (!event)
+			continue;
+		dsu_pmu_event_update(event);
+		dsu_pmu_set_event_period(event);
+		handled = true;
+	}
+
+	return IRQ_RETVAL(handled);
+}
+
+static void dsu_pmu_start(struct perf_event *event, int pmu_flags)
+{
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(event->pmu);
+
+	/* We always reprogram the counter */
+	if (pmu_flags & PERF_EF_RELOAD)
+		WARN_ON(!(event->hw.state & PERF_HES_UPTODATE));
+	dsu_pmu_set_event_period(event);
+	if (event->hw.idx != DSU_PMU_IDX_CYCLE_COUNTER)
+		dsu_pmu_set_event(dsu_pmu, event);
+	event->hw.state = 0;
+	dsu_pmu_enable_counter(dsu_pmu, event->hw.idx);
+}
+
+static void dsu_pmu_stop(struct perf_event *event, int pmu_flags)
+{
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(event->pmu);
+
+	if (event->hw.state & PERF_HES_STOPPED)
+		return;
+	dsu_pmu_disable_counter(dsu_pmu, event->hw.idx);
+	dsu_pmu_event_update(event);
+	event->hw.state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
+}
+
+static int dsu_pmu_add(struct perf_event *event, int flags)
+{
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(event->pmu);
+	struct dsu_hw_events *hw_events = &dsu_pmu->hw_events;
+	struct hw_perf_event *hwc = &event->hw;
+	int idx;
+
+	if (WARN_ON_ONCE(!cpumask_test_cpu(smp_processor_id(),
+					   &dsu_pmu->associated_cpus)))
+		return -ENOENT;
+
+	idx = dsu_pmu_get_event_idx(hw_events, event);
+	if (idx < 0)
+		return idx;
+
+	hwc->idx = idx;
+	hw_events->events[idx] = event;
+	hwc->state = PERF_HES_STOPPED | PERF_HES_UPTODATE;
+
+	if (flags & PERF_EF_START)
+		dsu_pmu_start(event, PERF_EF_RELOAD);
+
+	perf_event_update_userpage(event);
+	return 0;
+}
+
+static void dsu_pmu_del(struct perf_event *event, int flags)
+{
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(event->pmu);
+	struct dsu_hw_events *hw_events = &dsu_pmu->hw_events;
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+
+	dsu_pmu_stop(event, PERF_EF_UPDATE);
+	hw_events->events[idx] = NULL;
+	clear_bit(idx, hw_events->used_mask);
+	perf_event_update_userpage(event);
+}
+
+static void dsu_pmu_enable(struct pmu *pmu)
+{
+	u32 pmcr;
+	unsigned long flags;
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(pmu);
+
+	/* If no counters are added, skip enabling the PMU */
+	if (bitmap_empty(dsu_pmu->hw_events.used_mask, DSU_PMU_MAX_HW_CNTRS))
+		return;
+
+	raw_spin_lock_irqsave(&dsu_pmu->pmu_lock, flags);
+	pmcr = __dsu_pmu_read_pmcr();
+	pmcr |= CLUSTERPMCR_E;
+	__dsu_pmu_write_pmcr(pmcr);
+	raw_spin_unlock_irqrestore(&dsu_pmu->pmu_lock, flags);
+}
+
+static void dsu_pmu_disable(struct pmu *pmu)
+{
+	u32 pmcr;
+	unsigned long flags;
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(pmu);
+
+	raw_spin_lock_irqsave(&dsu_pmu->pmu_lock, flags);
+	pmcr = __dsu_pmu_read_pmcr();
+	pmcr &= ~CLUSTERPMCR_E;
+	__dsu_pmu_write_pmcr(pmcr);
+	raw_spin_unlock_irqrestore(&dsu_pmu->pmu_lock, flags);
+}
+
+static bool dsu_pmu_validate_event(struct pmu *pmu,
+				  struct dsu_hw_events *hw_events,
+				  struct perf_event *event)
+{
+	if (is_software_event(event))
+		return true;
+	/* Reject groups spanning multiple HW PMUs. */
+	if (event->pmu != pmu)
+		return false;
+	return dsu_pmu_get_event_idx(hw_events, event) >= 0;
+}
+
+/*
+ * Make sure the group of events can be scheduled at once
+ * on the PMU.
+ */
+static bool dsu_pmu_validate_group(struct perf_event *event)
+{
+	struct perf_event *sibling, *leader = event->group_leader;
+	struct dsu_hw_events fake_hw;
+
+	if (event->group_leader == event)
+		return true;
+
+	memset(fake_hw.used_mask, 0, sizeof(fake_hw.used_mask));
+	if (!dsu_pmu_validate_event(event->pmu, &fake_hw, leader))
+		return false;
+	list_for_each_entry(sibling, &leader->sibling_list, group_entry) {
+		if (!dsu_pmu_validate_event(event->pmu, &fake_hw, sibling))
+			return false;
+	}
+	return dsu_pmu_validate_event(event->pmu, &fake_hw, event);
+}
+
+static int dsu_pmu_event_init(struct perf_event *event)
+{
+	struct dsu_pmu *dsu_pmu = to_dsu_pmu(event->pmu);
+
+	if (event->attr.type != event->pmu->type)
+		return -ENOENT;
+
+	/* We don't support sampling */
+	if (is_sampling_event(event)) {
+		dev_dbg(dsu_pmu->pmu.dev, "Can't support sampling events\n");
+		return -EOPNOTSUPP;
+	}
+
+	/* We cannot support task bound events */
+	if (event->cpu < 0 || event->attach_state & PERF_ATTACH_TASK) {
+		dev_dbg(dsu_pmu->pmu.dev, "Can't support per-task counters\n");
+		return -EINVAL;
+	}
+
+	if (has_branch_stack(event) ||
+	    event->attr.exclude_user ||
+	    event->attr.exclude_kernel ||
+	    event->attr.exclude_hv ||
+	    event->attr.exclude_idle ||
+	    event->attr.exclude_host ||
+	    event->attr.exclude_guest) {
+		dev_dbg(dsu_pmu->pmu.dev, "Can't support filtering\n");
+		return -EINVAL;
+	}
+
+	if (!cpumask_test_cpu(event->cpu, &dsu_pmu->associated_cpus)) {
+		dev_dbg(dsu_pmu->pmu.dev,
+			 "Requested cpu is not associated with the DSU\n");
+		return -EINVAL;
+	}
+	/*
+	 * Choose the current active CPU to read the events. We don't want
+	 * to migrate the event contexts, irq handling etc to the requested
+	 * CPU. As long as the requested CPU is within the same DSU, we
+	 * are fine.
+	 */
+	event->cpu = cpumask_first(&dsu_pmu->active_cpu);
+	if (event->cpu >= nr_cpu_ids)
+		return -EINVAL;
+	if (!dsu_pmu_validate_group(event))
+		return -EINVAL;
+
+	event->hw.config_base = event->attr.config;
+	return 0;
+}
+
+static struct dsu_pmu *dsu_pmu_alloc(struct platform_device *pdev)
+{
+	struct dsu_pmu *dsu_pmu;
+
+	dsu_pmu = devm_kzalloc(&pdev->dev, sizeof(*dsu_pmu), GFP_KERNEL);
+	if (!dsu_pmu)
+		return ERR_PTR(-ENOMEM);
+
+	raw_spin_lock_init(&dsu_pmu->pmu_lock);
+	/*
+	 * Initialise the number of counters to -1, until we probe
+	 * the real number on a connected CPU.
+	 */
+	dsu_pmu->num_counters = -1;
+	return dsu_pmu;
+}
+
+/**
+ * dsu_pmu_dt_get_cpus: Get the list of CPUs in the cluster.
+ */
+static int dsu_pmu_dt_get_cpus(struct device_node *dev, cpumask_t *mask)
+{
+	int i = 0, n, cpu;
+	struct device_node *cpu_node;
+
+	n = of_count_phandle_with_args(dev, "cpus", NULL);
+	if (n <= 0)
+		return -ENODEV;
+	for (; i < n; i++) {
+		cpu_node = of_parse_phandle(dev, "cpus", i);
+		if (!cpu_node)
+			break;
+		cpu = of_cpu_node_to_id(cpu_node);
+		of_node_put(cpu_node);
+		/*
+		 * We have to ignore the failures here and continue scanning
+		 * the list to handle cases where the nr_cpus could be capped
+		 * in the running kernel.
+		 */
+		if (cpu < 0)
+			continue;
+		cpumask_set_cpu(cpu, mask);
+	}
+	return 0;
+}
+
+/*
+ * dsu_pmu_probe_pmu: Probe the PMU details on a CPU in the cluster.
+ */
+static void dsu_pmu_probe_pmu(struct dsu_pmu *dsu_pmu)
+{
+	u64 num_counters;
+	u32 cpmceid[2];
+
+	num_counters = (__dsu_pmu_read_pmcr() >> CLUSTERPMCR_N_SHIFT) &
+						CLUSTERPMCR_N_MASK;
+	/* We can only support up to 31 independent counters */
+	if (WARN_ON(num_counters > 31))
+		num_counters = 31;
+	dsu_pmu->num_counters = num_counters;
+	if (!dsu_pmu->num_counters)
+		return;
+	cpmceid[0] = __dsu_pmu_read_pmceid(0);
+	cpmceid[1] = __dsu_pmu_read_pmceid(1);
+	bitmap_from_u32array(dsu_pmu->cpmceid_bitmap,
+				DSU_PMU_MAX_COMMON_EVENTS,
+				cpmceid,
+				ARRAY_SIZE(cpmceid));
+}
+
+static void dsu_pmu_set_active_cpu(int cpu, struct dsu_pmu *dsu_pmu)
+{
+	cpumask_set_cpu(cpu, &dsu_pmu->active_cpu);
+	if (irq_set_affinity_hint(dsu_pmu->irq, &dsu_pmu->active_cpu))
+		pr_warn("Failed to set irq affinity to %d\n", cpu);
+}
+
+/*
+ * dsu_pmu_init_pmu: Initialise the DSU PMU configurations if
+ * we haven't done it already.
+ */
+static void dsu_pmu_init_pmu(struct dsu_pmu *dsu_pmu)
+{
+	if (dsu_pmu->num_counters == -1)
+		dsu_pmu_probe_pmu(dsu_pmu);
+	/* Reset the interrupt overflow mask */
+	dsu_pmu_get_reset_overflow();
+}
+
+static int dsu_pmu_device_probe(struct platform_device *pdev)
+{
+	int irq, rc;
+	struct dsu_pmu *dsu_pmu;
+	char *name;
+	static atomic_t pmu_idx = ATOMIC_INIT(-1);
+
+	dsu_pmu = dsu_pmu_alloc(pdev);
+	if (IS_ERR(dsu_pmu))
+		return PTR_ERR(dsu_pmu);
+
+	rc = dsu_pmu_dt_get_cpus(pdev->dev.of_node, &dsu_pmu->associated_cpus);
+	if (rc) {
+		dev_warn(&pdev->dev, "Failed to parse the CPUs\n");
+		return rc;
+	}
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_warn(&pdev->dev, "Failed to find IRQ\n");
+		return -EINVAL;
+	}
+
+	name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "%s_%d",
+				PMUNAME, atomic_inc_return(&pmu_idx));
+	if (!name)
+		return -ENOMEM;
+	rc = devm_request_irq(&pdev->dev, irq, dsu_pmu_handle_irq,
+			      IRQF_NOBALANCING, name, dsu_pmu);
+	if (rc) {
+		dev_warn(&pdev->dev, "Failed to request IRQ %d\n", irq);
+		return rc;
+	}
+
+	dsu_pmu->irq = irq;
+	platform_set_drvdata(pdev, dsu_pmu);
+	rc = cpuhp_state_add_instance(dsu_pmu_cpuhp_state,
+						&dsu_pmu->cpuhp_node);
+	if (rc)
+		return rc;
+
+	dsu_pmu->pmu = (struct pmu) {
+		.task_ctx_nr	= perf_invalid_context,
+		.module		= THIS_MODULE,
+		.pmu_enable	= dsu_pmu_enable,
+		.pmu_disable	= dsu_pmu_disable,
+		.event_init	= dsu_pmu_event_init,
+		.add		= dsu_pmu_add,
+		.del		= dsu_pmu_del,
+		.start		= dsu_pmu_start,
+		.stop		= dsu_pmu_stop,
+		.read		= dsu_pmu_read,
+
+		.attr_groups	= dsu_pmu_attr_groups,
+	};
+
+	rc = perf_pmu_register(&dsu_pmu->pmu, name, -1);
+	if (rc) {
+		cpuhp_state_remove_instance(dsu_pmu_cpuhp_state,
+						 &dsu_pmu->cpuhp_node);
+		irq_set_affinity_hint(dsu_pmu->irq, NULL);
+	}
+
+	return rc;
+}
+
+static int dsu_pmu_device_remove(struct platform_device *pdev)
+{
+	struct dsu_pmu *dsu_pmu = platform_get_drvdata(pdev);
+
+	perf_pmu_unregister(&dsu_pmu->pmu);
+	cpuhp_state_remove_instance(dsu_pmu_cpuhp_state, &dsu_pmu->cpuhp_node);
+	irq_set_affinity_hint(dsu_pmu->irq, NULL);
+
+	return 0;
+}
+
+static const struct of_device_id dsu_pmu_of_match[] = {
+	{ .compatible = "arm,dsu-pmu", },
+	{},
+};
+
+static struct platform_driver dsu_pmu_driver = {
+	.driver = {
+		.name	= DRVNAME,
+		.of_match_table = of_match_ptr(dsu_pmu_of_match),
+	},
+	.probe = dsu_pmu_device_probe,
+	.remove = dsu_pmu_device_remove,
+};
+
+static int dsu_pmu_cpu_online(unsigned int cpu, struct hlist_node *node)
+{
+	struct dsu_pmu *dsu_pmu = hlist_entry_safe(node, struct dsu_pmu,
+						   cpuhp_node);
+
+	if (!cpumask_test_cpu(cpu, &dsu_pmu->associated_cpus))
+		return 0;
+
+	/* If the PMU is already managed, there is nothing to do */
+	if (!cpumask_empty(&dsu_pmu->active_cpu))
+		return 0;
+
+	dsu_pmu_init_pmu(dsu_pmu);
+	dsu_pmu_set_active_cpu(cpu, dsu_pmu);
+
+	return 0;
+}
+
+static int dsu_pmu_cpu_teardown(unsigned int cpu, struct hlist_node *node)
+{
+	int dst;
+	struct dsu_pmu *dsu_pmu = hlist_entry_safe(node, struct dsu_pmu,
+						   cpuhp_node);
+
+	if (!cpumask_test_and_clear_cpu(cpu, &dsu_pmu->active_cpu))
+		return 0;
+
+	dst = dsu_pmu_get_online_cpu_any_but(dsu_pmu, cpu);
+	/* If there are no active CPUs in the DSU, leave IRQ disabled */
+	if (dst >= nr_cpu_ids) {
+		irq_set_affinity_hint(dsu_pmu->irq, NULL);
+		return 0;
+	}
+
+	perf_pmu_migrate_context(&dsu_pmu->pmu, cpu, dst);
+	dsu_pmu_set_active_cpu(dst, dsu_pmu);
+
+	return 0;
+}
+
+static int __init dsu_pmu_init(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
+					DRVNAME,
+					dsu_pmu_cpu_online,
+					dsu_pmu_cpu_teardown);
+	if (ret < 0)
+		return ret;
+	dsu_pmu_cpuhp_state = ret;
+	return platform_driver_register(&dsu_pmu_driver);
+}
+
+static void __exit dsu_pmu_exit(void)
+{
+	platform_driver_unregister(&dsu_pmu_driver);
+	cpuhp_remove_multi_state(dsu_pmu_cpuhp_state);
+}
+
+module_init(dsu_pmu_init);
+module_exit(dsu_pmu_exit);
+
+MODULE_DEVICE_TABLE(of, dsu_pmu_of_match);
+MODULE_DESCRIPTION("Perf driver for ARM DynamIQ Shared Unit");
+MODULE_AUTHOR("Suzuki K Poulose <suzuki.poulose@arm.com>");
+MODULE_LICENSE("GPL v2");