Subject: [PATCH v6 6/6] perf: ARM DynamIQ Shared Unit PMU support

From: [email-masked] (Jonathan Cameron)
Date: Tue, 22 Aug 2017 12:17:22 +0100

On Mon, 21 Aug 2017 18:55:09 +0100
Suzuki K Poulose <[email-masked]> wrote:

> 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 <[email-masked]>
> Cc: Will Deacon <[email-masked]>
> Signed-off-by: Suzuki K Poulose <[email-masked]>

Hi Suzuki,

Was just reading this again out of curiosity and picked up on a couple of
really trivial things.  Nothing that should slow down a merge, but if you happen
to be doing a v6...

Driver looks good to me.

Reviewed-by: Jonathan Cameron <[email-masked]>

Jonathan

> ---
> Changes since V5:
>  - Address comments on V5 by Mark.
>  - Use IRQ_NOBALANCING for IRQ handler
>  - Don't expose events which could be unimplemented.
>  - Get rid of dsu_pmu_event_supported and allow raw event
>    code to be used without validating whether it is supported.
>  - Rename "supported_cpus" mask to "associated_cpus"
>  - Add Documentation for the PMU driver
>  - Don't disable IRQ for dsu_pmu_{enable/disable}_counters
>  - Use consistent return codes for validate_event/group calls.
>  - Check PERF_ATTACH_TASK flag in event_init.
>  - Allow missing CPUs in dsu_pmu_dt_get_cpus, to handle cases
>    where kernel could have capped nr_cpus.
>  - Cleanup sanity checking for the CPU before accessing DSU
>  - Reject events with counting CPU not associated with the DSU.
> Changes since V4:
>  - Reflect the changed generic helper for mapping CPU id
> Changes since V2:
>  - Cleanup dsu_pmu_device_probe error handling.
>  - Fix event validate_group to invert the result check of validate_event
>  - Return errors if we failed to parse CPUs in the DSU.
>  - Add MODULE_DEVICE_TABLE entry
>  - Use hlist_entry_safe for converting cpuhp_node to dsu_pmu.
> ---
>  Documentation/perf/arm_dsu_pmu.txt   |  28 ++
>  arch/arm64/include/asm/arm_dsu_pmu.h | 124 ++++++
>  drivers/perf/Kconfig                 |   9 +
>  drivers/perf/Makefile                |   1 +
>  drivers/perf/arm_dsu_pmu.c           | 828 +++++++++++++++++++++++++++++++++++
>  5 files changed, 990 insertions(+)
>  create mode 100644 Documentation/perf/arm_dsu_pmu.txt
>  create mode 100644 arch/arm64/include/asm/arm_dsu_pmu.h
>  create mode 100644 drivers/perf/arm_dsu_pmu.c
> 
> diff --git a/Documentation/perf/arm_dsu_pmu.txt b/Documentation/perf/arm_dsu_pmu.txt
> new file mode 100644
> index 0000000..d611e15
> --- /dev/null
> +++ b/Documentation/perf/arm_dsu_pmu.txt
> @@ -0,0 +1,28 @@
> +ARM DynamIQ Shared Unit (DSU) PMU
> +==================================
> +
> +ARM DynamIQ Shared Unit 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 the L3 cache, Snoop Control Unit
> +etc, using 32bit independent counters. It also provides a 64bit cycle counter.
> +
> +The PMU can only be accessed via CPU system registers and are common to the
> +cores connected to the same DSU. Like most of the other uncore PMUs, DSU
> +PMU doesn't support process specific events and cannot be used in sampling mode.
> +
> +The DSU provides a bitmap for a subset of implemented events via hardware
> +registers. There is no way for the driver to determine if the other events
> +are available or not. Hence the driver exposes only those events advertised
> +by the DSU, in "events" directory under :
> +
> +  /sys/bus/event_sources/devices/arm_dsu_<N>/
> +
> +The user should refer to the TRM of the product to figure out the supported events
> +and use the raw event code for the unlisted events.
> +
> +The driver also exposes the CPUs connected to the DSU instance in "associated_cpus".
> +
> +
> +e.g usage :
> +
> +	perf stat -a -e arm_dsu_0/cycles/
> diff --git a/arch/arm64/include/asm/arm_dsu_pmu.h b/arch/arm64/include/asm/arm_dsu_pmu.h
> new file mode 100644
> index 0000000..5d1b0d9
> --- /dev/null
> +++ b/arch/arm64/include/asm/arm_dsu_pmu.h
> @@ -0,0 +1,124 @@
> +/*
> + * ARM DynamIQ Shared Unit (DSU) PMU Low level register access routines.
> + *
> + * Copyright (C) ARM Limited, 2017.
> + *
> + * Author: Suzuki K Poulose <[email-masked]>
> + *
> + * 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.
> + */
> +
> +#include <asm/sysreg.h>
> +
> +
> +#define CLUSTERPMCR_EL1			sys_reg(3, 0, 15, 5, 0)
> +#define CLUSTERPMCNTENSET_EL1		sys_reg(3, 0, 15, 5, 1)
> +#define CLUSTERPMCNTENCLR_EL1		sys_reg(3, 0, 15, 5, 2)
> +#define CLUSTERPMOVSSET_EL1		sys_reg(3, 0, 15, 5, 3)
> +#define CLUSTERPMOVSCLR_EL1		sys_reg(3, 0, 15, 5, 4)
> +#define CLUSTERPMSELR_EL1		sys_reg(3, 0, 15, 5, 5)
> +#define CLUSTERPMINTENSET_EL1		sys_reg(3, 0, 15, 5, 6)
> +#define CLUSTERPMINTENCLR_EL1		sys_reg(3, 0, 15, 5, 7)
> +#define CLUSTERPMCCNTR_EL1		sys_reg(3, 0, 15, 6, 0)
> +#define CLUSTERPMXEVTYPER_EL1		sys_reg(3, 0, 15, 6, 1)
> +#define CLUSTERPMXEVCNTR_EL1		sys_reg(3, 0, 15, 6, 2)
> +#define CLUSTERPMMDCR_EL1		sys_reg(3, 0, 15, 6, 3)
> +#define CLUSTERPMCEID0_EL1		sys_reg(3, 0, 15, 6, 4)
> +#define CLUSTERPMCEID1_EL1		sys_reg(3, 0, 15, 6, 5)
> +
> +static inline u32 __dsu_pmu_read_pmcr(void)
> +{
> +	return read_sysreg_s(CLUSTERPMCR_EL1);
> +}
> +
> +static inline void __dsu_pmu_write_pmcr(u32 val)
> +{
> +	write_sysreg_s(val, CLUSTERPMCR_EL1);
> +	isb();
> +}
> +
> +static inline u32 __dsu_pmu_getreset_overflow(void)
> +{
> +	u32 val = read_sysreg_s(CLUSTERPMOVSCLR_EL1);
> +	/* Clear the bit */
> +	write_sysreg_s(val, CLUSTERPMOVSCLR_EL1);
> +	isb();
> +	return val;
> +}
> +
> +static inline void __dsu_pmu_select_counter(int counter)
> +{
> +	write_sysreg_s(counter, CLUSTERPMSELR_EL1);
> +	isb();
> +}
> +
> +static inline u64 __dsu_pmu_read_counter(int counter)
> +{
> +	__dsu_pmu_select_counter(counter);
> +	return read_sysreg_s(CLUSTERPMXEVCNTR_EL1);
> +}
> +
> +static inline void __dsu_pmu_write_counter(int counter, u64 val)
> +{
> +	__dsu_pmu_select_counter(counter);
> +	write_sysreg_s(val, CLUSTERPMXEVCNTR_EL1);
> +	isb();
> +}
> +
> +static inline void __dsu_pmu_set_event(int counter, u32 event)
> +{
> +	__dsu_pmu_select_counter(counter);
> +	write_sysreg_s(event, CLUSTERPMXEVTYPER_EL1);
> +	isb();
> +}
> +
> +static inline u64 __dsu_pmu_read_pmccntr(void)
> +{
> +	return read_sysreg_s(CLUSTERPMCCNTR_EL1);
> +}
> +
> +static inline void __dsu_pmu_write_pmccntr(u64 val)
> +{
> +	write_sysreg_s(val, CLUSTERPMCCNTR_EL1);
> +	isb();
> +}
> +
> +static inline void __dsu_pmu_disable_counter(int counter)
> +{
> +	write_sysreg_s(BIT(counter), CLUSTERPMCNTENCLR_EL1);
> +	isb();
> +}
> +
> +static inline void __dsu_pmu_enable_counter(int counter)
> +{
> +	write_sysreg_s(BIT(counter), CLUSTERPMCNTENSET_EL1);
> +	isb();
> +}
> +
> +static inline void __dsu_pmu_counter_interrupt_enable(int counter)
> +{
> +	write_sysreg_s(BIT(counter), CLUSTERPMINTENSET_EL1);
> +	isb();
> +}
> +
> +static inline void __dsu_pmu_counter_interrupt_disable(int counter)
> +{
> +	write_sysreg_s(BIT(counter), CLUSTERPMINTENCLR_EL1);
> +	isb();
> +}
> +
> +
> +static inline u32 __dsu_pmu_read_pmceid(int n)
> +{
> +	switch (n) {
> +	case 0:
> +		return read_sysreg_s(CLUSTERPMCEID0_EL1);
> +	case 1:
> +		return read_sysreg_s(CLUSTERPMCEID1_EL1);
> +	default:
> +		BUILD_BUG();
> +		return 0;
> +	}
> +}
> diff --git a/drivers/perf/Kconfig b/drivers/perf/Kconfig
> index e5197ff..ee3d7d1 100644
> --- a/drivers/perf/Kconfig
> +++ b/drivers/perf/Kconfig
> @@ -17,6 +17,15 @@ config ARM_PMU_ACPI
>  	depends on ARM_PMU && ACPI
>  	def_bool y
>  
> +config ARM_DSU_PMU
> +	tristate "ARM DynamIQ Shared Unit (DSU) PMU"
> +	depends on ARM64 && PERF_EVENTS
> +	  help
> +	  Provides support for performance monitor unit in ARM DynamIQ Shared
> +	  Unit (DSU). The DSU integrates one or more cores  with an L3 memory
> +	  system, control logic. The PMU allows counting various events related
> +	  to DSU.
> +
>  config QCOM_L2_PMU
>  	bool "Qualcomm Technologies L2-cache PMU"
>  	depends on ARCH_QCOM && ARM64 && ACPI
> diff --git a/drivers/perf/Makefile b/drivers/perf/Makefile
> index 6420bd4..0adb4f6 100644
> --- a/drivers/perf/Makefile
> +++ b/drivers/perf/Makefile
> @@ -1,5 +1,6 @@
>  obj-$(CONFIG_ARM_PMU) += arm_pmu.o arm_pmu_platform.o
>  obj-$(CONFIG_ARM_PMU_ACPI) += arm_pmu_acpi.o
> +obj-$(CONFIG_ARM_DSU_PMU) += arm_dsu_pmu.o
>  obj-$(CONFIG_QCOM_L2_PMU)	+= qcom_l2_pmu.o
>  obj-$(CONFIG_QCOM_L3_PMU) += qcom_l3_pmu.o
>  obj-$(CONFIG_XGENE_PMU) += xgene_pmu.o
> diff --git a/drivers/perf/arm_dsu_pmu.c b/drivers/perf/arm_dsu_pmu.c
> new file mode 100644
> index 0000000..623beeb
> --- /dev/null
> +++ b/drivers/perf/arm_dsu_pmu.c
> @@ -0,0 +1,828 @@
> +/*
> + * 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/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 <asm/arm_dsu_pmu.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

Trivial comment of the day - missing .

> + * @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_acecss, 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(struct dsu_pmu *dsu_pmu)
> +{
> +	return cpumask_first_and(&dsu_pmu->associated_cpus, cpu_online_mask);
> +}
> +
> +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 = 0;

I'm doing well on trivial comments today.  Val is always set so
no need to assign a default value here.

> +	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->active_cpu)))
> +		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->active_cpu)))
> +		return;
> +
> +	if (!dsu_pmu_counter_valid(dsu_pmu, idx)) {
> +		dev_err(event->pmu->dev,
> +			"writing to invalid counter %d\n", idx);
> +		return;
> +	}
> +
> +	val &= DSU_PMU_COUNTER_MASK(idx);

Seems a little odd to do this as opposed to error out if the value
is too large.  Perhaps a comment to justify?

> +	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_next_zero_bit(used_mask, dsu_pmu->num_counters, 0);
> +	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_getreset_overflow(void)
> +{
> +	return __dsu_pmu_getreset_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, workset;
> +
> +	overflow = dsu_pmu_getreset_overflow();
> +	bitmap_and(&workset, &overflow, hw_events->used_mask,
> +		   DSU_PMU_MAX_HW_CNTRS);
> +
> +	if (!workset)
> +		return IRQ_NONE;
> +
> +	for_each_set_bit(i, &workset, 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->active_cpu)))
> +		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);
> +	int enabled = bitmap_weight(dsu_pmu->hw_events.used_mask,
> +				    DSU_PMU_MAX_HW_CNTRS);

!bitmap_empty might be slightly cheaper as we don't actually care
about the weight.

> +
> +	if (!enabled)
> +		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 (!dsu_pmu_validate_group(event))
> +		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;
> +
> +	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);
> +	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(void *data)
> +{
> +	struct dsu_pmu *dsu_pmu = data;
> +	u64 num_counters;
> +	u32 cpmceid[2];
> +
> +	num_counters = (__dsu_pmu_read_pmcr() >> CLUSTERPMCR_N_SHIFT) &
> +						CLUSTERPMCR_N_MASK;
> +	/* We can only support upto 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 int dsu_pmu_device_probe(struct platform_device *pdev)
> +{
> +	int irq, rc, cpu;
> +	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;
> +	}
> +
> +	rc = smp_call_function_any(&dsu_pmu->associated_cpus,
> +					dsu_pmu_probe_pmu,
> +					dsu_pmu, 1);
> +	if (rc)
> +		return rc;
> +	if (!dsu_pmu->num_counters)
> +		return -ENODEV;
> +	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));
> +	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;
> +	}
> +
> +	/*
> +	 * Find one CPU in the DSU to handle the IRQs.
> +	 * It is highly unlikely that we would fail
> +	 * to find one, given the probing has succeeded.
> +	 */
> +	cpu = dsu_pmu_get_online_cpu(dsu_pmu);
> +	if (cpu >= nr_cpu_ids)
> +		return -ENODEV;
> +	cpumask_set_cpu(cpu, &dsu_pmu->active_cpu);
> +	rc = irq_set_affinity_hint(irq, &dsu_pmu->active_cpu);
> +	if (rc) {
> +		dev_warn(&pdev->dev, "Failed to force IRQ affinity for %d\n",
> +					 irq);
> +		return rc;
> +	}
> +
> +	platform_set_drvdata(pdev, dsu_pmu);
> +	rc = cpuhp_state_add_instance(dsu_pmu_cpuhp_state,
> +						&dsu_pmu->cpuhp_node);
> +	if (rc)
> +		goto irq_cleanup;
> +
> +	dsu_pmu->irq = irq;
> +	dsu_pmu->pmu = (struct pmu) {
> +		.task_ctx_nr	= perf_invalid_context,
> +
> +		.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)
> +		goto cpuhp_cleanup;
> +
> +	dev_info(&pdev->dev, "Registered %s with %d event counters",
> +				name, dsu_pmu->num_counters);
> +	return 0;
> +
> +cpuhp_cleanup:
> +	cpuhp_state_remove_instance(dsu_pmu_cpuhp_state, &dsu_pmu->cpuhp_node);
> +irq_cleanup:
> +	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_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 (dst < nr_cpu_ids) {
> +		cpumask_set_cpu(dst, &dsu_pmu->active_cpu);
> +		perf_pmu_migrate_context(&dsu_pmu->pmu, cpu, dst);
> +		irq_set_affinity_hint(dsu_pmu->irq, &dsu_pmu->active_cpu);
> +	}
> +
> +	return 0;
> +}
> +
> +static int __init dsu_pmu_init(void)
> +{
> +	int ret;
> +
> +	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
> +					DRVNAME,
> +					NULL,
> +					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 <[email-masked]>");
> +MODULE_LICENSE("GPL v2");