perf: add qcom l2 cache perf events driver

Adds perf events support for L2 cache PMU.

The L2 cache PMU driver is named 'l2cache_0' and can be used
with perf events to profile L2 events such as cache hits
and misses on Qualcomm Technologies processors.

Reviewed-by: Mark Rutland <[e-mail]>
Signed-off-by: Neil Leeder <[e-mail]>
[will: minimise nesting in l2_cache_associate_cpu_with_cluster]
[will: use kstrtoul for unsigned long, remove redunant .owner setting]
Signed-off-by: Will Deacon <[e-mail]>

Documentation/perf/qcom_l2_pmu.txt

···
+Qualcomm Technologies Level-2 Cache Performance Monitoring Unit (PMU)
+=====================================================================
+
+This driver supports the L2 cache clusters found in Qualcomm Technologies
+Centriq SoCs. There are multiple physical L2 cache clusters, each with their
+own PMU. Each cluster has one or more CPUs associated with it.
+
+There is one logical L2 PMU exposed, which aggregates the results from
+the physical PMUs.
+
+The driver provides a description of its available events and configuration
+options in sysfs, see /sys/devices/l2cache_0.
+
+The "format" directory describes the format of the events.
+
+Events can be envisioned as a 2-dimensional array. Each column represents
+a group of events. There are 8 groups. Only one entry from each
+group can be in use at a time. If multiple events from the same group
+are specified, the conflicting events cannot be counted at the same time.
+
+Events are specified as 0xCCG, where CC is 2 hex digits specifying
+the code (array row) and G specifies the group (column) 0-7.
+
+In addition there is a cycle counter event specified by the value 0xFE
+which is outside the above scheme.
+
+The driver provides a "cpumask" sysfs attribute which contains a mask
+consisting of one CPU per cluster which will be used to handle all the PMU
+events on that cluster.
+
+Examples for use with perf:
+
+  perf stat -e l2cache_0/config=0x001/,l2cache_0/config=0x042/ -a sleep 1
+
+  perf stat -e l2cache_0/config=0xfe/ -C 2 sleep 1
+
+The driver does not support sampling, therefore "perf record" will
+not work. Per-task perf sessions are not supported.

drivers/perf/Kconfig

···
 	  Say y if you want to use CPU performance monitors on ARM-based
 	  systems.
 
+config QCOM_L2_PMU
+	bool "Qualcomm Technologies L2-cache PMU"
+	depends on ARCH_QCOM && ARM64 && PERF_EVENTS && ACPI
+	  help
+	  Provides support for the L2 cache performance monitor unit (PMU)
+	  in Qualcomm Technologies processors.
+	  Adds the L2 cache PMU into the perf events subsystem for
+	  monitoring L2 cache events.
+
 config XGENE_PMU
         depends on PERF_EVENTS && ARCH_XGENE
         bool "APM X-Gene SoC PMU"

drivers/perf/Makefile

···
 obj-$(CONFIG_ARM_PMU) += arm_pmu.o
+obj-$(CONFIG_QCOM_L2_PMU)	+= qcom_l2_pmu.o
 obj-$(CONFIG_XGENE_PMU) += xgene_pmu.o

drivers/perf/qcom_l2_pmu.c

···
+/* Copyright (c) 2015-2017 The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/acpi.h>
+#include <linux/bitops.h>
+#include <linux/bug.h>
+#include <linux/cpuhotplug.h>
+#include <linux/cpumask.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/percpu.h>
+#include <linux/perf_event.h>
+#include <linux/platform_device.h>
+#include <linux/smp.h>
+#include <linux/spinlock.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include <asm/barrier.h>
+#include <asm/local64.h>
+#include <asm/sysreg.h>
+
+#define MAX_L2_CTRS             9
+
+#define L2PMCR_NUM_EV_SHIFT     11
+#define L2PMCR_NUM_EV_MASK      0x1F
+
+#define L2PMCR                  0x400
+#define L2PMCNTENCLR            0x403
+#define L2PMCNTENSET            0x404
+#define L2PMINTENCLR            0x405
+#define L2PMINTENSET            0x406
+#define L2PMOVSCLR              0x407
+#define L2PMOVSSET              0x408
+#define L2PMCCNTCR              0x409
+#define L2PMCCNTR               0x40A
+#define L2PMCCNTSR              0x40C
+#define L2PMRESR                0x410
+#define IA_L2PMXEVCNTCR_BASE    0x420
+#define IA_L2PMXEVCNTR_BASE     0x421
+#define IA_L2PMXEVFILTER_BASE   0x423
+#define IA_L2PMXEVTYPER_BASE    0x424
+
+#define IA_L2_REG_OFFSET        0x10
+
+#define L2PMXEVFILTER_SUFILTER_ALL      0x000E0000
+#define L2PMXEVFILTER_ORGFILTER_IDINDEP 0x00000004
+#define L2PMXEVFILTER_ORGFILTER_ALL     0x00000003
+
+#define L2EVTYPER_REG_SHIFT     3
+
+#define L2PMRESR_GROUP_BITS     8
+#define L2PMRESR_GROUP_MASK     GENMASK(7, 0)
+
+#define L2CYCLE_CTR_BIT         31
+#define L2CYCLE_CTR_RAW_CODE    0xFE
+
+#define L2PMCR_RESET_ALL        0x6
+#define L2PMCR_COUNTERS_ENABLE  0x1
+#define L2PMCR_COUNTERS_DISABLE 0x0
+
+#define L2PMRESR_EN             BIT_ULL(63)
+
+#define L2_EVT_MASK             0x00000FFF
+#define L2_EVT_CODE_MASK        0x00000FF0
+#define L2_EVT_GRP_MASK         0x0000000F
+#define L2_EVT_CODE_SHIFT       4
+#define L2_EVT_GRP_SHIFT        0
+
+#define L2_EVT_CODE(event)   (((event) & L2_EVT_CODE_MASK) >> L2_EVT_CODE_SHIFT)
+#define L2_EVT_GROUP(event)  (((event) & L2_EVT_GRP_MASK) >> L2_EVT_GRP_SHIFT)
+
+#define L2_EVT_GROUP_MAX        7
+
+#define L2_COUNTER_RELOAD       BIT_ULL(31)
+#define L2_CYCLE_COUNTER_RELOAD BIT_ULL(63)
+
+#define L2CPUSRSELR_EL1         sys_reg(3, 3, 15, 0, 6)
+#define L2CPUSRDR_EL1           sys_reg(3, 3, 15, 0, 7)
+
+#define reg_idx(reg, i)         (((i) * IA_L2_REG_OFFSET) + reg##_BASE)
+
+static DEFINE_RAW_SPINLOCK(l2_access_lock);
+
+/**
+ * set_l2_indirect_reg: write value to an L2 register
+ * @reg: Address of L2 register.
+ * @value: Value to be written to register.
+ *
+ * Use architecturally required barriers for ordering between system register
+ * accesses
+ */
+static void set_l2_indirect_reg(u64 reg, u64 val)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&l2_access_lock, flags);
+	write_sysreg_s(reg, L2CPUSRSELR_EL1);
+	isb();
+	write_sysreg_s(val, L2CPUSRDR_EL1);
+	isb();
+	raw_spin_unlock_irqrestore(&l2_access_lock, flags);
+}
+
+/**
+ * get_l2_indirect_reg: read an L2 register value
+ * @reg: Address of L2 register.
+ *
+ * Use architecturally required barriers for ordering between system register
+ * accesses
+ */
+static u64 get_l2_indirect_reg(u64 reg)
+{
+	u64 val;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&l2_access_lock, flags);
+	write_sysreg_s(reg, L2CPUSRSELR_EL1);
+	isb();
+	val = read_sysreg_s(L2CPUSRDR_EL1);
+	raw_spin_unlock_irqrestore(&l2_access_lock, flags);
+
+	return val;
+}
+
+struct cluster_pmu;
+
+/*
+ * Aggregate PMU. Implements the core pmu functions and manages
+ * the hardware PMUs.
+ */
+struct l2cache_pmu {
+	struct hlist_node node;
+	u32 num_pmus;
+	struct pmu pmu;
+	int num_counters;
+	cpumask_t cpumask;
+	struct platform_device *pdev;
+	struct cluster_pmu * __percpu *pmu_cluster;
+	struct list_head clusters;
+};
+
+/*
+ * The cache is made up of one or more clusters, each cluster has its own PMU.
+ * Each cluster is associated with one or more CPUs.
+ * This structure represents one of the hardware PMUs.
+ *
+ * Events can be envisioned as a 2-dimensional array. Each column represents
+ * a group of events. There are 8 groups. Only one entry from each
+ * group can be in use at a time.
+ *
+ * Events are specified as 0xCCG, where CC is 2 hex digits specifying
+ * the code (array row) and G specifies the group (column).
+ *
+ * In addition there is a cycle counter event specified by L2CYCLE_CTR_RAW_CODE
+ * which is outside the above scheme.
+ */
+struct cluster_pmu {
+	struct list_head next;
+	struct perf_event *events[MAX_L2_CTRS];
+	struct l2cache_pmu *l2cache_pmu;
+	DECLARE_BITMAP(used_counters, MAX_L2_CTRS);
+	DECLARE_BITMAP(used_groups, L2_EVT_GROUP_MAX + 1);
+	int irq;
+	int cluster_id;
+	/* The CPU that is used for collecting events on this cluster */
+	int on_cpu;
+	/* All the CPUs associated with this cluster */
+	cpumask_t cluster_cpus;
+	spinlock_t pmu_lock;
+};
+
+#define to_l2cache_pmu(p) (container_of(p, struct l2cache_pmu, pmu))
+
+static u32 l2_cycle_ctr_idx;
+static u32 l2_counter_present_mask;
+
+static inline u32 idx_to_reg_bit(u32 idx)
+{
+	if (idx == l2_cycle_ctr_idx)
+		return BIT(L2CYCLE_CTR_BIT);
+
+	return BIT(idx);
+}
+
+static inline struct cluster_pmu *get_cluster_pmu(
+	struct l2cache_pmu *l2cache_pmu, int cpu)
+{
+	return *per_cpu_ptr(l2cache_pmu->pmu_cluster, cpu);
+}
+
+static void cluster_pmu_reset(void)
+{
+	/* Reset all counters */
+	set_l2_indirect_reg(L2PMCR, L2PMCR_RESET_ALL);
+	set_l2_indirect_reg(L2PMCNTENCLR, l2_counter_present_mask);
+	set_l2_indirect_reg(L2PMINTENCLR, l2_counter_present_mask);
+	set_l2_indirect_reg(L2PMOVSCLR, l2_counter_present_mask);
+}
+
+static inline void cluster_pmu_enable(void)
+{
+	set_l2_indirect_reg(L2PMCR, L2PMCR_COUNTERS_ENABLE);
+}
+
+static inline void cluster_pmu_disable(void)
+{
+	set_l2_indirect_reg(L2PMCR, L2PMCR_COUNTERS_DISABLE);
+}
+
+static inline void cluster_pmu_counter_set_value(u32 idx, u64 value)
+{
+	if (idx == l2_cycle_ctr_idx)
+		set_l2_indirect_reg(L2PMCCNTR, value);
+	else
+		set_l2_indirect_reg(reg_idx(IA_L2PMXEVCNTR, idx), value);
+}
+
+static inline u64 cluster_pmu_counter_get_value(u32 idx)
+{
+	u64 value;
+
+	if (idx == l2_cycle_ctr_idx)
+		value = get_l2_indirect_reg(L2PMCCNTR);
+	else
+		value = get_l2_indirect_reg(reg_idx(IA_L2PMXEVCNTR, idx));
+
+	return value;
+}
+
+static inline void cluster_pmu_counter_enable(u32 idx)
+{
+	set_l2_indirect_reg(L2PMCNTENSET, idx_to_reg_bit(idx));
+}
+
+static inline void cluster_pmu_counter_disable(u32 idx)
+{
+	set_l2_indirect_reg(L2PMCNTENCLR, idx_to_reg_bit(idx));
+}
+
+static inline void cluster_pmu_counter_enable_interrupt(u32 idx)
+{
+	set_l2_indirect_reg(L2PMINTENSET, idx_to_reg_bit(idx));
+}
+
+static inline void cluster_pmu_counter_disable_interrupt(u32 idx)
+{
+	set_l2_indirect_reg(L2PMINTENCLR, idx_to_reg_bit(idx));
+}
+
+static inline void cluster_pmu_set_evccntcr(u32 val)
+{
+	set_l2_indirect_reg(L2PMCCNTCR, val);
+}
+
+static inline void cluster_pmu_set_evcntcr(u32 ctr, u32 val)
+{
+	set_l2_indirect_reg(reg_idx(IA_L2PMXEVCNTCR, ctr), val);
+}
+
+static inline void cluster_pmu_set_evtyper(u32 ctr, u32 val)
+{
+	set_l2_indirect_reg(reg_idx(IA_L2PMXEVTYPER, ctr), val);
+}
+
+static void cluster_pmu_set_resr(struct cluster_pmu *cluster,
+			       u32 event_group, u32 event_cc)
+{
+	u64 field;
+	u64 resr_val;
+	u32 shift;
+	unsigned long flags;
+
+	shift = L2PMRESR_GROUP_BITS * event_group;
+	field = ((u64)(event_cc & L2PMRESR_GROUP_MASK) << shift);
+
+	spin_lock_irqsave(&cluster->pmu_lock, flags);
+
+	resr_val = get_l2_indirect_reg(L2PMRESR);
+	resr_val &= ~(L2PMRESR_GROUP_MASK << shift);
+	resr_val |= field;
+	resr_val |= L2PMRESR_EN;
+	set_l2_indirect_reg(L2PMRESR, resr_val);
+
+	spin_unlock_irqrestore(&cluster->pmu_lock, flags);
+}
+
+/*
+ * Hardware allows filtering of events based on the originating
+ * CPU. Turn this off by setting filter bits to allow events from
+ * all CPUS, subunits and ID independent events in this cluster.
+ */
+static inline void cluster_pmu_set_evfilter_sys_mode(u32 ctr)
+{
+	u32 val =  L2PMXEVFILTER_SUFILTER_ALL |
+		   L2PMXEVFILTER_ORGFILTER_IDINDEP |
+		   L2PMXEVFILTER_ORGFILTER_ALL;
+
+	set_l2_indirect_reg(reg_idx(IA_L2PMXEVFILTER, ctr), val);
+}
+
+static inline u32 cluster_pmu_getreset_ovsr(void)
+{
+	u32 result = get_l2_indirect_reg(L2PMOVSSET);
+
+	set_l2_indirect_reg(L2PMOVSCLR, result);
+	return result;
+}
+
+static inline bool cluster_pmu_has_overflowed(u32 ovsr)
+{
+	return !!(ovsr & l2_counter_present_mask);
+}
+
+static inline bool cluster_pmu_counter_has_overflowed(u32 ovsr, u32 idx)
+{
+	return !!(ovsr & idx_to_reg_bit(idx));
+}
+
+static void l2_cache_event_update(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	u64 delta, prev, now;
+	u32 idx = hwc->idx;
+
+	do {
+		prev = local64_read(&hwc->prev_count);
+		now = cluster_pmu_counter_get_value(idx);
+	} while (local64_cmpxchg(&hwc->prev_count, prev, now) != prev);
+
+	/*
+	 * The cycle counter is 64-bit, but all other counters are
+	 * 32-bit, and we must handle 32-bit overflow explicitly.
+	 */
+	delta = now - prev;
+	if (idx != l2_cycle_ctr_idx)
+		delta &= 0xffffffff;
+
+	local64_add(delta, &event->count);
+}
+
+static void l2_cache_cluster_set_period(struct cluster_pmu *cluster,
+				       struct hw_perf_event *hwc)
+{
+	u32 idx = hwc->idx;
+	u64 new;
+
+	/*
+	 * We limit the max period to half the max counter value so
+	 * that even in the case of extreme interrupt latency the
+	 * counter will (hopefully) not wrap past its initial value.
+	 */
+	if (idx == l2_cycle_ctr_idx)
+		new = L2_CYCLE_COUNTER_RELOAD;
+	else
+		new = L2_COUNTER_RELOAD;
+
+	local64_set(&hwc->prev_count, new);
+	cluster_pmu_counter_set_value(idx, new);
+}
+
+static int l2_cache_get_event_idx(struct cluster_pmu *cluster,
+				   struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	int idx;
+	int num_ctrs = cluster->l2cache_pmu->num_counters - 1;
+	unsigned int group;
+
+	if (hwc->config_base == L2CYCLE_CTR_RAW_CODE) {
+		if (test_and_set_bit(l2_cycle_ctr_idx, cluster->used_counters))
+			return -EAGAIN;
+
+		return l2_cycle_ctr_idx;
+	}
+
+	idx = find_first_zero_bit(cluster->used_counters, num_ctrs);
+	if (idx == num_ctrs)
+		/* The counters are all in use. */
+		return -EAGAIN;
+
+	/*
+	 * Check for column exclusion: event column already in use by another
+	 * event. This is for events which are not in the same group.
+	 * Conflicting events in the same group are detected in event_init.
+	 */
+	group = L2_EVT_GROUP(hwc->config_base);
+	if (test_bit(group, cluster->used_groups))
+		return -EAGAIN;
+
+	set_bit(idx, cluster->used_counters);
+	set_bit(group, cluster->used_groups);
+
+	return idx;
+}
+
+static void l2_cache_clear_event_idx(struct cluster_pmu *cluster,
+				      struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+
+	clear_bit(idx, cluster->used_counters);
+	if (hwc->config_base != L2CYCLE_CTR_RAW_CODE)
+		clear_bit(L2_EVT_GROUP(hwc->config_base), cluster->used_groups);
+}
+
+static irqreturn_t l2_cache_handle_irq(int irq_num, void *data)
+{
+	struct cluster_pmu *cluster = data;
+	int num_counters = cluster->l2cache_pmu->num_counters;
+	u32 ovsr;
+	int idx;
+
+	ovsr = cluster_pmu_getreset_ovsr();
+	if (!cluster_pmu_has_overflowed(ovsr))
+		return IRQ_NONE;
+
+	for_each_set_bit(idx, cluster->used_counters, num_counters) {
+		struct perf_event *event = cluster->events[idx];
+		struct hw_perf_event *hwc;
+
+		if (WARN_ON_ONCE(!event))
+			continue;
+
+		if (!cluster_pmu_counter_has_overflowed(ovsr, idx))
+			continue;
+
+		l2_cache_event_update(event);
+		hwc = &event->hw;
+
+		l2_cache_cluster_set_period(cluster, hwc);
+	}
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * Implementation of abstract pmu functionality required by
+ * the core perf events code.
+ */
+
+static void l2_cache_pmu_enable(struct pmu *pmu)
+{
+	/*
+	 * Although there is only one PMU (per socket) controlling multiple
+	 * physical PMUs (per cluster), because we do not support per-task mode
+	 * each event is associated with a CPU. Each event has pmu_enable
+	 * called on its CPU, so here it is only necessary to enable the
+	 * counters for the current CPU.
+	 */
+
+	cluster_pmu_enable();
+}
+
+static void l2_cache_pmu_disable(struct pmu *pmu)
+{
+	cluster_pmu_disable();
+}
+
+static int l2_cache_event_init(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	struct cluster_pmu *cluster;
+	struct perf_event *sibling;
+	struct l2cache_pmu *l2cache_pmu;
+
+	if (event->attr.type != event->pmu->type)
+		return -ENOENT;
+
+	l2cache_pmu = to_l2cache_pmu(event->pmu);
+
+	if (hwc->sample_period) {
+		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+				    "Sampling not supported\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (event->cpu < 0) {
+		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+				    "Per-task mode not supported\n");
+		return -EOPNOTSUPP;
+	}
+
+	/* We cannot filter accurately so we just don't allow it. */
+	if (event->attr.exclude_user || event->attr.exclude_kernel ||
+	    event->attr.exclude_hv || event->attr.exclude_idle) {
+		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+				    "Can't exclude execution levels\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (((L2_EVT_GROUP(event->attr.config) > L2_EVT_GROUP_MAX) ||
+	     ((event->attr.config & ~L2_EVT_MASK) != 0)) &&
+	    (event->attr.config != L2CYCLE_CTR_RAW_CODE)) {
+		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+				    "Invalid config %llx\n",
+				    event->attr.config);
+		return -EINVAL;
+	}
+
+	/* Don't allow groups with mixed PMUs, except for s/w events */
+	if (event->group_leader->pmu != event->pmu &&
+	    !is_software_event(event->group_leader)) {
+		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+			 "Can't create mixed PMU group\n");
+		return -EINVAL;
+	}
+
+	list_for_each_entry(sibling, &event->group_leader->sibling_list,
+			    group_entry)
+		if (sibling->pmu != event->pmu &&
+		    !is_software_event(sibling)) {
+			dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+				 "Can't create mixed PMU group\n");
+			return -EINVAL;
+		}
+
+	cluster = get_cluster_pmu(l2cache_pmu, event->cpu);
+	if (!cluster) {
+		/* CPU has not been initialised */
+		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+			"CPU%d not associated with L2 cluster\n", event->cpu);
+		return -EINVAL;
+	}
+
+	/* Ensure all events in a group are on the same cpu */
+	if ((event->group_leader != event) &&
+	    (cluster->on_cpu != event->group_leader->cpu)) {
+		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+			 "Can't create group on CPUs %d and %d",
+			 event->cpu, event->group_leader->cpu);
+		return -EINVAL;
+	}
+
+	if ((event != event->group_leader) &&
+	    (L2_EVT_GROUP(event->group_leader->attr.config) ==
+	     L2_EVT_GROUP(event->attr.config))) {
+		dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+			 "Column exclusion: conflicting events %llx %llx\n",
+		       event->group_leader->attr.config,
+		       event->attr.config);
+		return -EINVAL;
+	}
+
+	list_for_each_entry(sibling, &event->group_leader->sibling_list,
+			    group_entry) {
+		if ((sibling != event) &&
+		    (L2_EVT_GROUP(sibling->attr.config) ==
+		     L2_EVT_GROUP(event->attr.config))) {
+			dev_dbg_ratelimited(&l2cache_pmu->pdev->dev,
+			     "Column exclusion: conflicting events %llx %llx\n",
+					    sibling->attr.config,
+					    event->attr.config);
+			return -EINVAL;
+		}
+	}
+
+	hwc->idx = -1;
+	hwc->config_base = event->attr.config;
+
+	/*
+	 * Ensure all events are on the same cpu so all events are in the
+	 * same cpu context, to avoid races on pmu_enable etc.
+	 */
+	event->cpu = cluster->on_cpu;
+
+	return 0;
+}
+
+static void l2_cache_event_start(struct perf_event *event, int flags)
+{
+	struct cluster_pmu *cluster;
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+	u32 config;
+	u32 event_cc, event_group;
+
+	hwc->state = 0;
+
+	cluster = get_cluster_pmu(to_l2cache_pmu(event->pmu), event->cpu);
+
+	l2_cache_cluster_set_period(cluster, hwc);
+
+	if (hwc->config_base == L2CYCLE_CTR_RAW_CODE) {
+		cluster_pmu_set_evccntcr(0);
+	} else {
+		config = hwc->config_base;
+		event_cc    = L2_EVT_CODE(config);
+		event_group = L2_EVT_GROUP(config);
+
+		cluster_pmu_set_evcntcr(idx, 0);
+		cluster_pmu_set_evtyper(idx, event_group);
+		cluster_pmu_set_resr(cluster, event_group, event_cc);
+		cluster_pmu_set_evfilter_sys_mode(idx);
+	}
+
+	cluster_pmu_counter_enable_interrupt(idx);
+	cluster_pmu_counter_enable(idx);
+}
+
+static void l2_cache_event_stop(struct perf_event *event, int flags)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+
+	if (hwc->state & PERF_HES_STOPPED)
+		return;
+
+	cluster_pmu_counter_disable_interrupt(idx);
+	cluster_pmu_counter_disable(idx);
+
+	if (flags & PERF_EF_UPDATE)
+		l2_cache_event_update(event);
+	hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
+}
+
+static int l2_cache_event_add(struct perf_event *event, int flags)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	int idx;
+	int err = 0;
+	struct cluster_pmu *cluster;
+
+	cluster = get_cluster_pmu(to_l2cache_pmu(event->pmu), event->cpu);
+
+	idx = l2_cache_get_event_idx(cluster, event);
+	if (idx < 0)
+		return idx;
+
+	hwc->idx = idx;
+	hwc->state = PERF_HES_STOPPED | PERF_HES_UPTODATE;
+	cluster->events[idx] = event;
+	local64_set(&hwc->prev_count, 0);
+
+	if (flags & PERF_EF_START)
+		l2_cache_event_start(event, flags);
+
+	/* Propagate changes to the userspace mapping. */
+	perf_event_update_userpage(event);
+
+	return err;
+}
+
+static void l2_cache_event_del(struct perf_event *event, int flags)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	struct cluster_pmu *cluster;
+	int idx = hwc->idx;
+
+	cluster = get_cluster_pmu(to_l2cache_pmu(event->pmu), event->cpu);
+
+	l2_cache_event_stop(event, flags | PERF_EF_UPDATE);
+	cluster->events[idx] = NULL;
+	l2_cache_clear_event_idx(cluster, event);
+
+	perf_event_update_userpage(event);
+}
+
+static void l2_cache_event_read(struct perf_event *event)
+{
+	l2_cache_event_update(event);
+}
+
+static ssize_t l2_cache_pmu_cpumask_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct l2cache_pmu *l2cache_pmu = to_l2cache_pmu(dev_get_drvdata(dev));
+
+	return cpumap_print_to_pagebuf(true, buf, &l2cache_pmu->cpumask);
+}
+
+static struct device_attribute l2_cache_pmu_cpumask_attr =
+		__ATTR(cpumask, S_IRUGO, l2_cache_pmu_cpumask_show, NULL);
+
+static struct attribute *l2_cache_pmu_cpumask_attrs[] = {
+	&l2_cache_pmu_cpumask_attr.attr,
+	NULL,
+};
+
+static struct attribute_group l2_cache_pmu_cpumask_group = {
+	.attrs = l2_cache_pmu_cpumask_attrs,
+};
+
+/* CCG format for perf RAW codes. */
+PMU_FORMAT_ATTR(l2_code,   "config:4-11");
+PMU_FORMAT_ATTR(l2_group,  "config:0-3");
+static struct attribute *l2_cache_pmu_formats[] = {
+	&format_attr_l2_code.attr,
+	&format_attr_l2_group.attr,
+	NULL,
+};
+
+static struct attribute_group l2_cache_pmu_format_group = {
+	.name = "format",
+	.attrs = l2_cache_pmu_formats,
+};
+
+static const struct attribute_group *l2_cache_pmu_attr_grps[] = {
+	&l2_cache_pmu_format_group,
+	&l2_cache_pmu_cpumask_group,
+	NULL,
+};
+
+/*
+ * Generic device handlers
+ */
+
+static const struct acpi_device_id l2_cache_pmu_acpi_match[] = {
+	{ "QCOM8130", },
+	{ }
+};
+
+static int get_num_counters(void)
+{
+	int val;
+
+	val = get_l2_indirect_reg(L2PMCR);
+
+	/*
+	 * Read number of counters from L2PMCR and add 1
+	 * for the cycle counter.
+	 */
+	return ((val >> L2PMCR_NUM_EV_SHIFT) & L2PMCR_NUM_EV_MASK) + 1;
+}
+
+static struct cluster_pmu *l2_cache_associate_cpu_with_cluster(
+	struct l2cache_pmu *l2cache_pmu, int cpu)
+{
+	u64 mpidr;
+	int cpu_cluster_id;
+	struct cluster_pmu *cluster = NULL;
+
+	/*
+	 * This assumes that the cluster_id is in MPIDR[aff1] for
+	 * single-threaded cores, and MPIDR[aff2] for multi-threaded
+	 * cores. This logic will have to be updated if this changes.
+	 */
+	mpidr = read_cpuid_mpidr();
+	if (mpidr & MPIDR_MT_BITMASK)
+		cpu_cluster_id = MPIDR_AFFINITY_LEVEL(mpidr, 2);
+	else
+		cpu_cluster_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
+
+	list_for_each_entry(cluster, &l2cache_pmu->clusters, next) {
+		if (cluster->cluster_id != cpu_cluster_id)
+			continue;
+
+		dev_info(&l2cache_pmu->pdev->dev,
+			 "CPU%d associated with cluster %d\n", cpu,
+			 cluster->cluster_id);
+		cpumask_set_cpu(cpu, &cluster->cluster_cpus);
+		*per_cpu_ptr(l2cache_pmu->pmu_cluster, cpu) = cluster;
+		break;
+	}
+
+	return cluster;
+}
+
+static int l2cache_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
+{
+	struct cluster_pmu *cluster;
+	struct l2cache_pmu *l2cache_pmu;
+
+	l2cache_pmu = hlist_entry_safe(node, struct l2cache_pmu, node);
+	cluster = get_cluster_pmu(l2cache_pmu, cpu);
+	if (!cluster) {
+		/* First time this CPU has come online */
+		cluster = l2_cache_associate_cpu_with_cluster(l2cache_pmu, cpu);
+		if (!cluster) {
+			/* Only if broken firmware doesn't list every cluster */
+			WARN_ONCE(1, "No L2 cache cluster for CPU%d\n", cpu);
+			return 0;
+		}
+	}
+
+	/* If another CPU is managing this cluster, we're done */
+	if (cluster->on_cpu != -1)
+		return 0;
+
+	/*
+	 * All CPUs on this cluster were down, use this one.
+	 * Reset to put it into sane state.
+	 */
+	cluster->on_cpu = cpu;
+	cpumask_set_cpu(cpu, &l2cache_pmu->cpumask);
+	cluster_pmu_reset();
+
+	WARN_ON(irq_set_affinity(cluster->irq, cpumask_of(cpu)));
+	enable_irq(cluster->irq);
+
+	return 0;
+}
+
+static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
+{
+	struct cluster_pmu *cluster;
+	struct l2cache_pmu *l2cache_pmu;
+	cpumask_t cluster_online_cpus;
+	unsigned int target;
+
+	l2cache_pmu = hlist_entry_safe(node, struct l2cache_pmu, node);
+	cluster = get_cluster_pmu(l2cache_pmu, cpu);
+	if (!cluster)
+		return 0;
+
+	/* If this CPU is not managing the cluster, we're done */
+	if (cluster->on_cpu != cpu)
+		return 0;
+
+	/* Give up ownership of cluster */
+	cpumask_clear_cpu(cpu, &l2cache_pmu->cpumask);
+	cluster->on_cpu = -1;
+
+	/* Any other CPU for this cluster which is still online */
+	cpumask_and(&cluster_online_cpus, &cluster->cluster_cpus,
+		    cpu_online_mask);
+	target = cpumask_any_but(&cluster_online_cpus, cpu);
+	if (target >= nr_cpu_ids) {
+		disable_irq(cluster->irq);
+		return 0;
+	}
+
+	perf_pmu_migrate_context(&l2cache_pmu->pmu, cpu, target);
+	cluster->on_cpu = target;
+	cpumask_set_cpu(target, &l2cache_pmu->cpumask);
+	WARN_ON(irq_set_affinity(cluster->irq, cpumask_of(target)));
+
+	return 0;
+}
+
+static int l2_cache_pmu_probe_cluster(struct device *dev, void *data)
+{
+	struct platform_device *pdev = to_platform_device(dev->parent);
+	struct platform_device *sdev = to_platform_device(dev);
+	struct l2cache_pmu *l2cache_pmu = data;
+	struct cluster_pmu *cluster;
+	struct acpi_device *device;
+	unsigned long fw_cluster_id;
+	int err;
+	int irq;
+
+	if (acpi_bus_get_device(ACPI_HANDLE(dev), &device))
+		return -ENODEV;
+
+	if (kstrtoul(device->pnp.unique_id, 10, &fw_cluster_id) < 0) {
+		dev_err(&pdev->dev, "unable to read ACPI uid\n");
+		return -ENODEV;
+	}
+
+	cluster = devm_kzalloc(&pdev->dev, sizeof(*cluster), GFP_KERNEL);
+	if (!cluster)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&cluster->next);
+	list_add(&cluster->next, &l2cache_pmu->clusters);
+	cluster->cluster_id = fw_cluster_id;
+
+	irq = platform_get_irq(sdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev,
+			"Failed to get valid irq for cluster %ld\n",
+			fw_cluster_id);
+		return irq;
+	}
+	irq_set_status_flags(irq, IRQ_NOAUTOEN);
+	cluster->irq = irq;
+
+	cluster->l2cache_pmu = l2cache_pmu;
+	cluster->on_cpu = -1;
+
+	err = devm_request_irq(&pdev->dev, irq, l2_cache_handle_irq,
+			       IRQF_NOBALANCING | IRQF_NO_THREAD,
+			       "l2-cache-pmu", cluster);
+	if (err) {
+		dev_err(&pdev->dev,
+			"Unable to request IRQ%d for L2 PMU counters\n", irq);
+		return err;
+	}
+
+	dev_info(&pdev->dev,
+		"Registered L2 cache PMU cluster %ld\n", fw_cluster_id);
+
+	spin_lock_init(&cluster->pmu_lock);
+
+	l2cache_pmu->num_pmus++;
+
+	return 0;
+}
+
+static int l2_cache_pmu_probe(struct platform_device *pdev)
+{
+	int err;
+	struct l2cache_pmu *l2cache_pmu;
+
+	l2cache_pmu =
+		devm_kzalloc(&pdev->dev, sizeof(*l2cache_pmu), GFP_KERNEL);
+	if (!l2cache_pmu)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&l2cache_pmu->clusters);
+
+	platform_set_drvdata(pdev, l2cache_pmu);
+	l2cache_pmu->pmu = (struct pmu) {
+		/* suffix is instance id for future use with multiple sockets */
+		.name		= "l2cache_0",
+		.task_ctx_nr    = perf_invalid_context,
+		.pmu_enable	= l2_cache_pmu_enable,
+		.pmu_disable	= l2_cache_pmu_disable,
+		.event_init	= l2_cache_event_init,
+		.add		= l2_cache_event_add,
+		.del		= l2_cache_event_del,
+		.start		= l2_cache_event_start,
+		.stop		= l2_cache_event_stop,
+		.read		= l2_cache_event_read,
+		.attr_groups	= l2_cache_pmu_attr_grps,
+	};
+
+	l2cache_pmu->num_counters = get_num_counters();
+	l2cache_pmu->pdev = pdev;
+	l2cache_pmu->pmu_cluster = devm_alloc_percpu(&pdev->dev,
+						     struct cluster_pmu *);
+	if (!l2cache_pmu->pmu_cluster)
+		return -ENOMEM;
+
+	l2_cycle_ctr_idx = l2cache_pmu->num_counters - 1;
+	l2_counter_present_mask = GENMASK(l2cache_pmu->num_counters - 2, 0) |
+		BIT(L2CYCLE_CTR_BIT);
+
+	cpumask_clear(&l2cache_pmu->cpumask);
+
+	/* Read cluster info and initialize each cluster */
+	err = device_for_each_child(&pdev->dev, l2cache_pmu,
+				    l2_cache_pmu_probe_cluster);
+	if (err)
+		return err;
+
+	if (l2cache_pmu->num_pmus == 0) {
+		dev_err(&pdev->dev, "No hardware L2 cache PMUs found\n");
+		return -ENODEV;
+	}
+
+	err = cpuhp_state_add_instance(CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
+				       &l2cache_pmu->node);
+	if (err) {
+		dev_err(&pdev->dev, "Error %d registering hotplug", err);
+		return err;
+	}
+
+	err = perf_pmu_register(&l2cache_pmu->pmu, l2cache_pmu->pmu.name, -1);
+	if (err) {
+		dev_err(&pdev->dev, "Error %d registering L2 cache PMU\n", err);
+		goto out_unregister;
+	}
+
+	dev_info(&pdev->dev, "Registered L2 cache PMU using %d HW PMUs\n",
+		 l2cache_pmu->num_pmus);
+
+	return err;
+
+out_unregister:
+	cpuhp_state_remove_instance(CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
+				    &l2cache_pmu->node);
+	return err;
+}
+
+static int l2_cache_pmu_remove(struct platform_device *pdev)
+{
+	struct l2cache_pmu *l2cache_pmu =
+		to_l2cache_pmu(platform_get_drvdata(pdev));
+
+	perf_pmu_unregister(&l2cache_pmu->pmu);
+	cpuhp_state_remove_instance(CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
+				    &l2cache_pmu->node);
+	return 0;
+}
+
+static struct platform_driver l2_cache_pmu_driver = {
+	.driver = {
+		.name = "qcom-l2cache-pmu",
+		.acpi_match_table = ACPI_PTR(l2_cache_pmu_acpi_match),
+	},
+	.probe = l2_cache_pmu_probe,
+	.remove = l2_cache_pmu_remove,
+};
+
+static int __init register_l2_cache_pmu_driver(void)
+{
+	int err;
+
+	err = cpuhp_setup_state_multi(CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
+				      "AP_PERF_ARM_QCOM_L2_ONLINE",
+				      l2cache_pmu_online_cpu,
+				      l2cache_pmu_offline_cpu);
+	if (err)
+		return err;
+
+	return platform_driver_register(&l2_cache_pmu_driver);
+}
+device_initcall(register_l2_cache_pmu_driver);

include/linux/cpuhotplug.h

···
 	CPUHP_AP_PERF_ARM_CCI_ONLINE,
 	CPUHP_AP_PERF_ARM_CCN_ONLINE,
 	CPUHP_AP_PERF_ARM_L2X0_ONLINE,
+	CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
 	CPUHP_AP_WORKQUEUE_ONLINE,
 	CPUHP_AP_RCUTREE_ONLINE,
 	CPUHP_AP_ONLINE_DYN,