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Subject: Re: [PATCH v4 1/2] perf: riscv: preliminary RISC-V support
To:     Alan Kao <alankao@andestech.com>,
        Palmer Dabbelt <palmer@sifive.com>,
        Albert Ou <albert@sifive.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Alex Solomatnikov <sols@sifive.com>,
        Jonathan Corbet <corbet@lwn.net>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc:     Nick Hu <nickhu@andestech.com>,
        Greentime Hu <greentime@andestech.com>
References: <1524017523-25076-1-git-send-email-alankao@andestech.com>
 <1524017523-25076-2-git-send-email-alankao@andestech.com>
From:   Atish Patra <atish.patra@wdc.com>
Message-ID: <c057c7d1-421f-f4eb-3f03-2abda16d876a@wdc.com>
Date:   Thu, 19 Apr 2018 12:46:24 -0700
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On 4/17/18 7:13 PM, Alan Kao wrote:
> This patch provide a basic PMU, riscv_base_pmu, which supports two
> general hardware event, instructions and cycles.  Furthermore, this
> PMU serves as a reference implementation to ease the portings in
> the future.
> 
> riscv_base_pmu should be able to run on any RISC-V machine that
> conforms to the Priv-Spec.  Note that the latest qemu model hasn't
> fully support a proper behavior of Priv-Spec 1.10 yet, but work
> around should be easy with very small fixes.  Please check
> https://github.com/riscv/riscv-qemu/pull/115 for future updates.
> 
> Cc: Nick Hu <nickhu@andestech.com>
> Cc: Greentime Hu <greentime@andestech.com>
> Signed-off-by: Alan Kao <alankao@andestech.com>
> ---
>   arch/riscv/Kconfig                  |  13 +
>   arch/riscv/include/asm/perf_event.h |  79 ++++-
>   arch/riscv/kernel/Makefile          |   1 +
>   arch/riscv/kernel/perf_event.c      | 482 ++++++++++++++++++++++++++++
>   4 files changed, 571 insertions(+), 4 deletions(-)
>   create mode 100644 arch/riscv/kernel/perf_event.c
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index c22ebe08e902..90d9c8e50377 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -203,6 +203,19 @@ config RISCV_ISA_C
>   config RISCV_ISA_A
>   	def_bool y
>   
> +menu "supported PMU type"
> +	depends on PERF_EVENTS
> +
> +config RISCV_BASE_PMU
> +	bool "Base Performance Monitoring Unit"
> +	def_bool y
> +	help
> +	  A base PMU that serves as a reference implementation and has limited
> +	  feature of perf.  It can run on any RISC-V machines so serves as the
> +	  fallback, but this option can also be disable to reduce kernel size.
> +
> +endmenu
> +
>   endmenu
>   
>   menu "Kernel type"
> diff --git a/arch/riscv/include/asm/perf_event.h b/arch/riscv/include/asm/perf_event.h
> index e13d2ff29e83..0e638a0c3feb 100644
> --- a/arch/riscv/include/asm/perf_event.h
> +++ b/arch/riscv/include/asm/perf_event.h
> @@ -1,13 +1,84 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
>   /*
>    * Copyright (C) 2018 SiFive
> + * Copyright (C) 2018 Andes Technology Corporation
>    *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of the GNU General Public Licence
> - * as published by the Free Software Foundation; either version
> - * 2 of the Licence, or (at your option) any later version.
>    */
>   
>   #ifndef _ASM_RISCV_PERF_EVENT_H
>   #define _ASM_RISCV_PERF_EVENT_H
>   
> +#include <linux/perf_event.h>
> +#include <linux/ptrace.h>
> +
> +#define RISCV_BASE_COUNTERS	2
> +
> +/*
> + * The RISCV_MAX_COUNTERS parameter should be specified.
> + */
> +
> +#ifdef CONFIG_RISCV_BASE_PMU
> +#define RISCV_MAX_COUNTERS	2
> +#endif
> +
> +#ifndef RISCV_MAX_COUNTERS
> +#error "Please provide a valid RISCV_MAX_COUNTERS for the PMU."
> +#endif
> +
> +/*
> + * These are the indexes of bits in counteren register *minus* 1,
> + * except for cycle.  It would be coherent if it can directly mapped
> + * to counteren bit definition, but there is a *time* register at
> + * counteren[1].  Per-cpu structure is scarce resource here.
> + *
> + * According to the spec, an implementation can support counter up to
> + * mhpmcounter31, but many high-end processors has at most 6 general
> + * PMCs, we give the definition to MHPMCOUNTER8 here.
> + */
> +#define RISCV_PMU_CYCLE		0
> +#define RISCV_PMU_INSTRET	1
> +#define RISCV_PMU_MHPMCOUNTER3	2
> +#define RISCV_PMU_MHPMCOUNTER4	3
> +#define RISCV_PMU_MHPMCOUNTER5	4
> +#define RISCV_PMU_MHPMCOUNTER6	5
> +#define RISCV_PMU_MHPMCOUNTER7	6
> +#define RISCV_PMU_MHPMCOUNTER8	7
> +
> +#define RISCV_OP_UNSUPP		(-EOPNOTSUPP)
> +
> +struct cpu_hw_events {
> +	/* # currently enabled events*/
> +	int			n_events;
> +	/* currently enabled events */
> +	struct perf_event	*events[RISCV_MAX_COUNTERS];
> +	/* vendor-defined PMU data */
> +	void			*platform;
> +};
> +
> +struct riscv_pmu {
> +	struct pmu	*pmu;
> +
> +	/* generic hw/cache events table */
> +	const int	*hw_events;
> +	const int	(*cache_events)[PERF_COUNT_HW_CACHE_MAX]
> +				       [PERF_COUNT_HW_CACHE_OP_MAX]
> +				       [PERF_COUNT_HW_CACHE_RESULT_MAX];
> +	/* method used to map hw/cache events */
> +	int		(*map_hw_event)(u64 config);
> +	int		(*map_cache_event)(u64 config);
> +
> +	/* max generic hw events in map */
> +	int		max_events;
> +	/* number total counters, 2(base) + x(general) */
> +	int		num_counters;
> +	/* the width of the counter */
> +	int		counter_width;
> +
> +	/* vendor-defined PMU features */
> +	void		*platform;
> +
> +	irqreturn_t	(*handle_irq)(int irq_num, void *dev);
> +	int		irq;
> +};
> +
>   #endif /* _ASM_RISCV_PERF_EVENT_H */
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index ffa439d4a364..f50d19816757 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -39,5 +39,6 @@ obj-$(CONFIG_MODULE_SECTIONS)	+= module-sections.o
>   obj-$(CONFIG_FUNCTION_TRACER)	+= mcount.o
>   obj-$(CONFIG_DYNAMIC_FTRACE)	+= mcount-dyn.o
>   obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o
> +obj-$(CONFIG_PERF_EVENTS)      += perf_event.o
>   
>   clean:
> diff --git a/arch/riscv/kernel/perf_event.c b/arch/riscv/kernel/perf_event.c
> new file mode 100644
> index 000000000000..ba3192afc470
> --- /dev/null
> +++ b/arch/riscv/kernel/perf_event.c
> @@ -0,0 +1,482 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
> + * Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
> + * Copyright (C) 2009 Jaswinder Singh Rajput
> + * Copyright (C) 2009 Advanced Micro Devices, Inc., Robert Richter
> + * Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra
> + * Copyright (C) 2009 Intel Corporation, <markus.t.metzger@intel.com>
> + * Copyright (C) 2009 Google, Inc., Stephane Eranian
> + * Copyright 2014 Tilera Corporation. All Rights Reserved.
> + * Copyright (C) 2018 Andes Technology Corporation
> + *
> + * Perf_events support for RISC-V platforms.
> + *
> + * Since the spec. (as of now, Priv-Spec 1.10) does not provide enough
> + * functionality for perf event to fully work, this file provides
> + * the very basic framework only.
> + *
> + * For platform portings, please check Documentations/riscv/pmu.txt.
> + *
> + * The Copyright line includes x86 and tile ones.
> + */
> +
> +#include <linux/kprobes.h>
> +#include <linux/kernel.h>
> +#include <linux/kdebug.h>
> +#include <linux/mutex.h>
> +#include <linux/bitmap.h>
> +#include <linux/irq.h>
> +#include <linux/interrupt.h>
> +#include <linux/perf_event.h>
> +#include <linux/atomic.h>
> +#include <linux/of.h>
> +#include <asm/perf_event.h>
> +
> +static const struct riscv_pmu *riscv_pmu __read_mostly;
> +static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);
> +
> +/*
> + * Hardware & cache maps and their methods
> + */
> +
> +static const int riscv_hw_event_map[] = {
> +	[PERF_COUNT_HW_CPU_CYCLES]		= RISCV_PMU_CYCLE,
> +	[PERF_COUNT_HW_INSTRUCTIONS]		= RISCV_PMU_INSTRET,
> +	[PERF_COUNT_HW_CACHE_REFERENCES]	= RISCV_OP_UNSUPP,
> +	[PERF_COUNT_HW_CACHE_MISSES]		= RISCV_OP_UNSUPP,
> +	[PERF_COUNT_HW_BRANCH_INSTRUCTIONS]	= RISCV_OP_UNSUPP,
> +	[PERF_COUNT_HW_BRANCH_MISSES]		= RISCV_OP_UNSUPP,
> +	[PERF_COUNT_HW_BUS_CYCLES]		= RISCV_OP_UNSUPP,
> +};
> +
> +#define C(x) PERF_COUNT_HW_CACHE_##x
> +static const int riscv_cache_event_map[PERF_COUNT_HW_CACHE_MAX]
> +[PERF_COUNT_HW_CACHE_OP_MAX]
> +[PERF_COUNT_HW_CACHE_RESULT_MAX] = {
> +	[C(L1D)] = {
> +		[C(OP_READ)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_WRITE)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_PREFETCH)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +	},
> +	[C(L1I)] = {
> +		[C(OP_READ)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_WRITE)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_PREFETCH)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +	},
> +	[C(LL)] = {
> +		[C(OP_READ)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_WRITE)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_PREFETCH)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +	},
> +	[C(DTLB)] = {
> +		[C(OP_READ)] = {
> +			[C(RESULT_ACCESS)] =  RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] =  RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_WRITE)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_PREFETCH)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +	},
> +	[C(ITLB)] = {
> +		[C(OP_READ)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_WRITE)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_PREFETCH)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +	},
> +	[C(BPU)] = {
> +		[C(OP_READ)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_WRITE)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +		[C(OP_PREFETCH)] = {
> +			[C(RESULT_ACCESS)] = RISCV_OP_UNSUPP,
> +			[C(RESULT_MISS)] = RISCV_OP_UNSUPP,
> +		},
> +	},
> +};
> +
> +static int riscv_map_hw_event(u64 config)
> +{
> +	if (config >= riscv_pmu->max_events)
> +		return -EINVAL;
> +
> +	return riscv_pmu->hw_events[config];
> +}
> +
> +int riscv_map_cache_decode(u64 config, unsigned int *type,
> +			   unsigned int *op, unsigned int *result)
> +{
> +	return -ENOENT;
> +}
> +
> +static int riscv_map_cache_event(u64 config)
> +{
> +	unsigned int type, op, result;
> +	int err = -ENOENT;
> +		int code;
> +
> +	err = riscv_map_cache_decode(config, &type, &op, &result);
> +	if (!riscv_pmu->cache_events || err)
> +		return err;
> +
> +	if (type >= PERF_COUNT_HW_CACHE_MAX ||
> +	    op >= PERF_COUNT_HW_CACHE_OP_MAX ||
> +	    result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
> +		return -EINVAL;
> +
> +	code = (*riscv_pmu->cache_events)[type][op][result];
> +	if (code == RISCV_OP_UNSUPP)
> +		return -EINVAL;
> +
> +	return code;
> +}
> +
> +/*
> + * Low-level functions: reading/writing counters
> + */
> +
> +static inline u64 read_counter(int idx)
> +{
> +	u64 val = 0;
> +
> +	switch (idx) {
> +	case RISCV_PMU_CYCLE:
> +		val = csr_read(cycle);
> +		break;
> +	case RISCV_PMU_INSTRET:
> +		val = csr_read(instret);
> +		break;
> +	default:
> +		WARN_ON_ONCE(idx < 0 ||	idx > RISCV_MAX_COUNTERS);
> +		return -EINVAL;
> +	}
> +
> +	return val;
> +}
> +
> +static inline void write_counter(int idx, u64 value)
> +{
> +	/* currently not supported */
> +	WARN_ON_ONCE(1);
> +}
> +
> +/*
> + * pmu->read: read and update the counter
> + *
> + * Other architectures' implementation often have a xxx_perf_event_update
> + * routine, which can return counter values when called in the IRQ, but
> + * return void when being called by the pmu->read method.
> + */
> +static void riscv_pmu_read(struct perf_event *event)
> +{
> +	struct hw_perf_event *hwc = &event->hw;
> +	u64 prev_raw_count, new_raw_count;
> +	u64 oldval;
> +	int idx = hwc->idx;
> +	u64 delta;
> +
> +	do {
> +		prev_raw_count = local64_read(&hwc->prev_count);
> +		new_raw_count = read_counter(idx);
> +
> +		oldval = local64_cmpxchg(&hwc->prev_count, prev_raw_count,
> +					 new_raw_count);
> +	} while (oldval != prev_raw_count);
> +
> +	/*
> +	 * delta is the value to update the counter we maintain in the kernel.
> +	 */
> +	delta = (new_raw_count - prev_raw_count) &
> +		((1ULL << riscv_pmu->counter_width) - 1);
> +	local64_add(delta, &event->count);
> +	/*
> +	 * Something like local64_sub(delta, &hwc->period_left) here is
> +	 * needed if there is an interrupt for perf.
> +	 */
> +}
> +
> +/*
> + * State transition functions:
> + *
> + * stop()/start() & add()/del()
> + */
> +
> +/*
> + * pmu->stop: stop the counter
> + */
> +static void riscv_pmu_stop(struct perf_event *event, int flags)
> +{
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
> +	hwc->state |= PERF_HES_STOPPED;
> +
> +	if ((flags & PERF_EF_UPDATE) && !(hwc->state & PERF_HES_UPTODATE)) {
> +		riscv_pmu->pmu->read(event);
> +		hwc->state |= PERF_HES_UPTODATE;
> +	}
> +}
> +
> +/*
> + * pmu->start: start the event.
> + */
> +static void riscv_pmu_start(struct perf_event *event, int flags)
> +{
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
> +		return;
> +
> +	if (flags & PERF_EF_RELOAD) {
> +		WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
> +
> +		/*
> +		 * Set the counter to the period to the next interrupt here,
> +		 * if you have any.
> +		 */
> +	}
> +
> +	hwc->state = 0;
> +	perf_event_update_userpage(event);
> +
> +	/*
> +	 * Since we cannot write to counters, this serves as an initialization
> +	 * to the delta-mechanism in pmu->read(); otherwise, the delta would be
> +	 * wrong when pmu->read is called for the first time.
> +	 */
> +	local64_set(&hwc->prev_count, read_counter(hwc->idx));
> +}
> +
> +/*
> + * pmu->add: add the event to PMU.
> + */
> +static int riscv_pmu_add(struct perf_event *event, int flags)
> +{
> +	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	if (cpuc->n_events == riscv_pmu->num_counters)
> +		return -ENOSPC;
> +
> +	/*
> +	 * We don't have general conunters, so no binding-event-to-counter
> +	 * process here.
> +	 *
> +	 * Indexing using hwc->config generally not works, since config may
> +	 * contain extra information, but here the only info we have in
> +	 * hwc->config is the event index.
> +	 */
> +	hwc->idx = hwc->config;
> +	cpuc->events[hwc->idx] = event;
> +	cpuc->n_events++;
> +
> +	hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
> +
> +	if (flags & PERF_EF_START)
> +		riscv_pmu->pmu->start(event, PERF_EF_RELOAD);
> +
> +	return 0;
> +}
> +
> +/*
> + * pmu->del: delete the event from PMU.
> + */
> +static void riscv_pmu_del(struct perf_event *event, int flags)
> +{
> +	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	cpuc->events[hwc->idx] = NULL;
> +	cpuc->n_events--;
> +	riscv_pmu->pmu->stop(event, PERF_EF_UPDATE);
> +	perf_event_update_userpage(event);
> +}
> +
> +/*
> + * Interrupt: a skeletion for reference.
> + */
> +
> +static DEFINE_MUTEX(pmc_reserve_mutex);
> +
> +irqreturn_t riscv_base_pmu_handle_irq(int irq_num, void *dev)
> +{
> +	return IRQ_NONE;
> +}
> +
> +static int reserve_pmc_hardware(void)
> +{
> +	int err = 0;
> +
> +	mutex_lock(&pmc_reserve_mutex);
> +	if (riscv_pmu->irq >=0 && riscv_pmu->handle_irq) {
> +		err = request_irq(riscv_pmu->irq, riscv_pmu->handle_irq,
> +				  IRQF_PERCPU, "riscv-base-perf", NULL);
> +	}
> +	mutex_unlock(&pmc_reserve_mutex);
> +
> +	return err;
> +}
> +
> +void release_pmc_hardware(void)
> +{
> +	mutex_lock(&pmc_reserve_mutex);
> +	if (riscv_pmu->irq >=0) {
> +		free_irq(riscv_pmu->irq, NULL);
> +	}
> +	mutex_unlock(&pmc_reserve_mutex);
> +}
> +
> +/*
> + * Event Initialization/Finalization
> + */
> +
> +static atomic_t riscv_active_events = ATOMIC_INIT(0);
> +
> +static void riscv_event_destroy(struct perf_event *event)
> +{
> +	if (atomic_dec_return(&riscv_active_events) == 0)
> +		release_pmc_hardware();
> +}
> +
> +static int riscv_event_init(struct perf_event *event)
> +{
> +	struct perf_event_attr *attr = &event->attr;
> +	struct hw_perf_event *hwc = &event->hw;
> +	int err;
> +	int code;
> +
> +	if (atomic_inc_return(&riscv_active_events) == 1) {
> +		err = reserve_pmc_hardware();
> +
> +		if (err) {
> +			pr_warn("PMC hardware not available\n");
> +			atomic_dec(&riscv_active_events);
> +			return -EBUSY;
> +		}
> +	}
> +
> +	switch (event->attr.type) {
> +	case PERF_TYPE_HARDWARE:
> +		code = riscv_pmu->map_hw_event(attr->config);
> +		break;
> +	case PERF_TYPE_HW_CACHE:
> +		code = riscv_pmu->map_cache_event(attr->config);
> +		break;
> +	case PERF_TYPE_RAW:
> +		return -EOPNOTSUPP;
> +	default:
> +		return -ENOENT;
> +	}
> +
> +	event->destroy = riscv_event_destroy;
> +	if (code < 0) {
> +		event->destroy(event);
> +		return code;
> +	}
> +
> +	/*
> +	 * idx is set to -1 because the index of a general event should not be
> +	 * decided until binding to some counter in pmu->add().
> +	 *
> +	 * But since we don't have such support, later in pmu->add(), we just
> +	 * use hwc->config as the index instead.
> +	 */
> +	hwc->config = code;
> +	hwc->idx = -1;
> +
> +	return 0;
> +}
> +
> +/*
> + * Initialization
> + */
> +
> +static struct pmu min_pmu = {
> +	.name		= "riscv-base",
> +	.event_init	= riscv_event_init,
> +	.add		= riscv_pmu_add,
> +	.del		= riscv_pmu_del,
> +	.start		= riscv_pmu_start,
> +	.stop		= riscv_pmu_stop,
> +	.read		= riscv_pmu_read,
> +};
> +
> +static const struct riscv_pmu riscv_base_pmu = {
> +	.pmu = &min_pmu,
> +	.max_events = ARRAY_SIZE(riscv_hw_event_map),
> +	.map_hw_event = riscv_map_hw_event,
> +	.hw_events = riscv_hw_event_map,
> +	.map_cache_event = riscv_map_cache_event,
> +	.cache_events = &riscv_cache_event_map,
> +	.counter_width = 63,
> +	.num_counters = RISCV_BASE_COUNTERS + 0,
> +	.handle_irq = &riscv_base_pmu_handle_irq,
> +
> +	/* This means this PMU has no IRQ. */
> +	.irq = -1,
> +};
> +
> +static const struct of_device_id riscv_pmu_of_ids[] = {
> +	{.compatible = "riscv,base-pmu",	.data = &riscv_base_pmu},
> +	{ /* sentinel value */ }
> +};
> +
> +int __init init_hw_perf_events(void)
> +{
> +	struct device_node *node = of_find_node_by_type(NULL, "pmu");
> +	const struct of_device_id *of_id;
> +	
> +	if (node && (of_id = of_match_node(riscv_pmu_of_ids, node)))
> +		riscv_pmu = of_id->data;
> +	else
> +		riscv_pmu = &riscv_base_pmu;
> +
> +	perf_pmu_register(riscv_pmu->pmu, "cpu", PERF_TYPE_RAW);
> +	return 0;
> +}
> +arch_initcall(init_hw_perf_events);
> 
Some check patch errors.

ERROR: spaces required around that '>=' (ctx:WxV)
#517: FILE: arch/riscv/kernel/perf_event.c:356:
+	if (riscv_pmu->irq >=0 && riscv_pmu->handle_irq) {
  	                   ^

ERROR: spaces required around that '>=' (ctx:WxV)
#529: FILE: arch/riscv/kernel/perf_event.c:368:
+	if (riscv_pmu->irq >=0) {
  	                   ^

WARNING: braces {} are not necessary for single statement blocks
#529: FILE: arch/riscv/kernel/perf_event.c:368:
+	if (riscv_pmu->irq >=0) {
+		free_irq(riscv_pmu->irq, NULL);
+	}

WARNING: DT compatible string "riscv,base-pmu" appears un-documented -- 
check ./Documentation/devicetree/bindings/
#626: FILE: arch/riscv/kernel/perf_event.c:465:
+	{.compatible = "riscv,base-pmu",	.data = &riscv_base_pmu},

ERROR: trailing whitespace
#634: FILE: arch/riscv/kernel/perf_event.c:473:
+^I$

ERROR: do not use assignment in if condition
#635: FILE: arch/riscv/kernel/perf_event.c:474:
+	if (node && (of_id = of_match_node(riscv_pmu_of_ids, node)))

total: 4 errors, 3 warnings, 595 lines checked


Regards,
Atish