xtensa: implement counting and sampling perf events

Xtensa Performance Monitor Module has up to 8 32 bit wide performance
counters. Each counter may be enabled independently and can count any
single type of hardware performance events. Event counting may be enabled
and disabled globally (per PMM).
Each counter has status register with bits indicating if the counter has
been overflown and may be programmed to raise profiling IRQ on overflow.
This IRQ is used to rewind counters and allow for counting more than 2^32
samples for counting events and to report samples for sampling events.

For more details see Tensilica Debug User's Guide, chapter 8
"Performance monitor module".

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -128,6 +128,16 @@ config XTENSA_VARIANT_MMU
 	  Build a Conventional Kernel with full MMU support,
 	  ie: it supports a TLB with auto-loading, page protection.
 
+config XTENSA_VARIANT_HAVE_PERF_EVENTS
+	bool "Core variant has Performance Monitor Module"
+	depends on XTENSA_VARIANT_CUSTOM
+	default n
+	help
+	  Enable if core variant has Performance Monitor Module with
+	  External Registers Interface.
+
+	  If unsure, say N.
+
 config XTENSA_UNALIGNED_USER
 	bool "Unaligned memory access in use space"
 	help

arch/xtensa/kernel/Makefile

@@ -13,6 +13,7 @@ obj-$(CONFIG_PCI) += pci.o
 obj-$(CONFIG_MODULES) += xtensa_ksyms.o module.o
 obj-$(CONFIG_FUNCTION_TRACER) += mcount.o
 obj-$(CONFIG_SMP) += smp.o mxhead.o
+obj-$(CONFIG_XTENSA_VARIANT_HAVE_PERF_EVENTS) += perf_event.o
 
 AFLAGS_head.o += -mtext-section-literals
 

arch/xtensa/kernel/perf_event.c

+/*
+ * Xtensa Performance Monitor Module driver
+ * See Tensilica Debug User's Guide for PMU registers documentation.
+ *
+ * Copyright (C) 2015 Cadence Design Systems Inc.
+ *
+ * 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 <linux/interrupt.h>
+#include <linux/irqdomain.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/perf_event.h>
+#include <linux/platform_device.h>
+
+#include <asm/processor.h>
+#include <asm/stacktrace.h>
+
+/* Global control/status for all perf counters */
+#define XTENSA_PMU_PMG			0x1000
+/* Perf counter values */
+#define XTENSA_PMU_PM(i)		(0x1080 + (i) * 4)
+/* Perf counter control registers */
+#define XTENSA_PMU_PMCTRL(i)		(0x1100 + (i) * 4)
+/* Perf counter status registers */
+#define XTENSA_PMU_PMSTAT(i)		(0x1180 + (i) * 4)
+
+#define XTENSA_PMU_PMG_PMEN		0x1
+
+#define XTENSA_PMU_COUNTER_MASK		0xffffffffULL
+#define XTENSA_PMU_COUNTER_MAX		0x7fffffff
+
+#define XTENSA_PMU_PMCTRL_INTEN		0x00000001
+#define XTENSA_PMU_PMCTRL_KRNLCNT	0x00000008
+#define XTENSA_PMU_PMCTRL_TRACELEVEL	0x000000f0
+#define XTENSA_PMU_PMCTRL_SELECT_SHIFT	8
+#define XTENSA_PMU_PMCTRL_SELECT	0x00001f00
+#define XTENSA_PMU_PMCTRL_MASK_SHIFT	16
+#define XTENSA_PMU_PMCTRL_MASK		0xffff0000
+
+#define XTENSA_PMU_MASK(select, mask) \
+	(((select) << XTENSA_PMU_PMCTRL_SELECT_SHIFT) | \
+	 ((mask) << XTENSA_PMU_PMCTRL_MASK_SHIFT) | \
+	 XTENSA_PMU_PMCTRL_TRACELEVEL | \
+	 XTENSA_PMU_PMCTRL_INTEN)
+
+#define XTENSA_PMU_PMSTAT_OVFL		0x00000001
+#define XTENSA_PMU_PMSTAT_INTASRT	0x00000010
+
+struct xtensa_pmu_events {
+	/* Array of events currently on this core */
+	struct perf_event *event[XCHAL_NUM_PERF_COUNTERS];
+	/* Bitmap of used hardware counters */
+	unsigned long used_mask[BITS_TO_LONGS(XCHAL_NUM_PERF_COUNTERS)];
+};
+static DEFINE_PER_CPU(struct xtensa_pmu_events, xtensa_pmu_events);
+
+static const u32 xtensa_hw_ctl[] = {
+	[PERF_COUNT_HW_CPU_CYCLES]		= XTENSA_PMU_MASK(0, 0x1),
+	[PERF_COUNT_HW_INSTRUCTIONS]		= XTENSA_PMU_MASK(2, 0xffff),
+	[PERF_COUNT_HW_CACHE_REFERENCES]	= XTENSA_PMU_MASK(10, 0x1),
+	[PERF_COUNT_HW_CACHE_MISSES]		= XTENSA_PMU_MASK(12, 0x1),
+	/* Taken and non-taken branches + taken loop ends */
+	[PERF_COUNT_HW_BRANCH_INSTRUCTIONS]	= XTENSA_PMU_MASK(2, 0x490),
+	/* Instruction-related + other global stall cycles */
+	[PERF_COUNT_HW_STALLED_CYCLES_FRONTEND]	= XTENSA_PMU_MASK(4, 0x1ff),
+	/* Data-related global stall cycles */
+	[PERF_COUNT_HW_STALLED_CYCLES_BACKEND]	= XTENSA_PMU_MASK(3, 0x1ff),
+};
+
+#define C(_x) PERF_COUNT_HW_CACHE_##_x
+
+static const u32 xtensa_cache_ctl[][C(OP_MAX)][C(RESULT_MAX)] = {
+	[C(L1D)] = {
+		[C(OP_READ)] = {
+			[C(RESULT_ACCESS)]	= XTENSA_PMU_MASK(10, 0x1),
+			[C(RESULT_MISS)]	= XTENSA_PMU_MASK(10, 0x2),
+		},
+		[C(OP_WRITE)] = {
+			[C(RESULT_ACCESS)]	= XTENSA_PMU_MASK(11, 0x1),
+			[C(RESULT_MISS)]	= XTENSA_PMU_MASK(11, 0x2),
+		},
+	},
+	[C(L1I)] = {
+		[C(OP_READ)] = {
+			[C(RESULT_ACCESS)]	= XTENSA_PMU_MASK(8, 0x1),
+			[C(RESULT_MISS)]	= XTENSA_PMU_MASK(8, 0x2),
+		},
+	},
+	[C(DTLB)] = {
+		[C(OP_READ)] = {
+			[C(RESULT_ACCESS)]	= XTENSA_PMU_MASK(9, 0x1),
+			[C(RESULT_MISS)]	= XTENSA_PMU_MASK(9, 0x8),
+		},
+	},
+	[C(ITLB)] = {
+		[C(OP_READ)] = {
+			[C(RESULT_ACCESS)]	= XTENSA_PMU_MASK(7, 0x1),
+			[C(RESULT_MISS)]	= XTENSA_PMU_MASK(7, 0x8),
+		},
+	},
+};
+
+static int xtensa_pmu_cache_event(u64 config)
+{
+	unsigned int cache_type, cache_op, cache_result;
+	int ret;
+
+	cache_type = (config >>  0) & 0xff;
+	cache_op = (config >>  8) & 0xff;
+	cache_result = (config >> 16) & 0xff;
+
+	if (cache_type >= ARRAY_SIZE(xtensa_cache_ctl) ||
+	    cache_op >= C(OP_MAX) ||
+	    cache_result >= C(RESULT_MAX))
+		return -EINVAL;
+
+	ret = xtensa_cache_ctl[cache_type][cache_op][cache_result];
+
+	if (ret == 0)
+		return -EINVAL;
+
+	return ret;
+}
+
+static inline uint32_t xtensa_pmu_read_counter(int idx)
+{
+	return get_er(XTENSA_PMU_PM(idx));
+}
+
+static inline void xtensa_pmu_write_counter(int idx, uint32_t v)
+{
+	set_er(v, XTENSA_PMU_PM(idx));
+}
+
+static void xtensa_perf_event_update(struct perf_event *event,
+				     struct hw_perf_event *hwc, int idx)
+{
+	uint64_t prev_raw_count, new_raw_count;
+	int64_t delta;
+
+	do {
+		prev_raw_count = local64_read(&hwc->prev_count);
+		new_raw_count = xtensa_pmu_read_counter(event->hw.idx);
+	} while (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
+				 new_raw_count) != prev_raw_count);
+
+	delta = (new_raw_count - prev_raw_count) & XTENSA_PMU_COUNTER_MASK;
+
+	local64_add(delta, &event->count);
+	local64_sub(delta, &hwc->period_left);
+}
+
+static bool xtensa_perf_event_set_period(struct perf_event *event,
+					 struct hw_perf_event *hwc, int idx)
+{
+	bool rc = false;
+	s64 left;
+
+	if (!is_sampling_event(event)) {
+		left = XTENSA_PMU_COUNTER_MAX;
+	} else {
+		s64 period = hwc->sample_period;
+
+		left = local64_read(&hwc->period_left);
+		if (left <= -period) {
+			left = period;
+			local64_set(&hwc->period_left, left);
+			hwc->last_period = period;
+			rc = true;
+		} else if (left <= 0) {
+			left += period;
+			local64_set(&hwc->period_left, left);
+			hwc->last_period = period;
+			rc = true;
+		}
+		if (left > XTENSA_PMU_COUNTER_MAX)
+			left = XTENSA_PMU_COUNTER_MAX;
+	}
+
+	local64_set(&hwc->prev_count, -left);
+	xtensa_pmu_write_counter(idx, -left);
+	perf_event_update_userpage(event);
+
+	return rc;
+}
+
+static void xtensa_pmu_enable(struct pmu *pmu)
+{
+	set_er(get_er(XTENSA_PMU_PMG) | XTENSA_PMU_PMG_PMEN, XTENSA_PMU_PMG);
+}
+
+static void xtensa_pmu_disable(struct pmu *pmu)
+{
+	set_er(get_er(XTENSA_PMU_PMG) & ~XTENSA_PMU_PMG_PMEN, XTENSA_PMU_PMG);
+}
+
+static int xtensa_pmu_event_init(struct perf_event *event)
+{
+	int ret;
+
+	switch (event->attr.type) {
+	case PERF_TYPE_HARDWARE:
+		if (event->attr.config >= ARRAY_SIZE(xtensa_hw_ctl) ||
+		    xtensa_hw_ctl[event->attr.config] == 0)
+			return -EINVAL;
+		event->hw.config = xtensa_hw_ctl[event->attr.config];
+		return 0;
+
+	case PERF_TYPE_HW_CACHE:
+		ret = xtensa_pmu_cache_event(event->attr.config);
+		if (ret < 0)
+			return ret;
+		event->hw.config = ret;
+		return 0;
+
+	case PERF_TYPE_RAW:
+		/* Not 'previous counter' select */
+		if ((event->attr.config & XTENSA_PMU_PMCTRL_SELECT) ==
+		    (1 << XTENSA_PMU_PMCTRL_SELECT_SHIFT))
+			return -EINVAL;
+		event->hw.config = (event->attr.config &
+				    (XTENSA_PMU_PMCTRL_KRNLCNT |
+				     XTENSA_PMU_PMCTRL_TRACELEVEL |
+				     XTENSA_PMU_PMCTRL_SELECT |
+				     XTENSA_PMU_PMCTRL_MASK)) |
+			XTENSA_PMU_PMCTRL_INTEN;
+		return 0;
+
+	default:
+		return -ENOENT;
+	}
+}
+
+/*
+ * Starts/Stops a counter present on the PMU. The PMI handler
+ * should stop the counter when perf_event_overflow() returns
+ * !0. ->start() will be used to continue.
+ */
+static void xtensa_pmu_start(struct perf_event *event, int flags)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+
+	if (WARN_ON_ONCE(idx == -1))
+		return;
+
+	if (flags & PERF_EF_RELOAD) {
+		WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
+		xtensa_perf_event_set_period(event, hwc, idx);
+	}
+
+	hwc->state = 0;
+
+	set_er(hwc->config, XTENSA_PMU_PMCTRL(idx));
+}
+
+static void xtensa_pmu_stop(struct perf_event *event, int flags)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+
+	if (!(hwc->state & PERF_HES_STOPPED)) {
+		set_er(0, XTENSA_PMU_PMCTRL(idx));
+		set_er(get_er(XTENSA_PMU_PMSTAT(idx)),
+		       XTENSA_PMU_PMSTAT(idx));
+		hwc->state |= PERF_HES_STOPPED;
+	}
+
+	if ((flags & PERF_EF_UPDATE) &&
+	    !(event->hw.state & PERF_HES_UPTODATE)) {
+		xtensa_perf_event_update(event, &event->hw, idx);
+		event->hw.state |= PERF_HES_UPTODATE;
+	}
+}
+
+/*
+ * Adds/Removes a counter to/from the PMU, can be done inside
+ * a transaction, see the ->*_txn() methods.
+ */
+static int xtensa_pmu_add(struct perf_event *event, int flags)
+{
+	struct xtensa_pmu_events *ev = this_cpu_ptr(&xtensa_pmu_events);
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+
+	if (__test_and_set_bit(idx, ev->used_mask)) {
+		idx = find_first_zero_bit(ev->used_mask,
+					  XCHAL_NUM_PERF_COUNTERS);
+		if (idx == XCHAL_NUM_PERF_COUNTERS)
+			return -EAGAIN;
+
+		__set_bit(idx, ev->used_mask);
+		hwc->idx = idx;
+	}
+	ev->event[idx] = event;
+
+	hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
+
+	if (flags & PERF_EF_START)
+		xtensa_pmu_start(event, PERF_EF_RELOAD);
+
+	perf_event_update_userpage(event);
+	return 0;
+}
+
+static void xtensa_pmu_del(struct perf_event *event, int flags)
+{
+	struct xtensa_pmu_events *ev = this_cpu_ptr(&xtensa_pmu_events);
+
+	xtensa_pmu_stop(event, PERF_EF_UPDATE);
+	__clear_bit(event->hw.idx, ev->used_mask);
+	perf_event_update_userpage(event);
+}
+
+static void xtensa_pmu_read(struct perf_event *event)
+{
+	xtensa_perf_event_update(event, &event->hw, event->hw.idx);
+}
+
+static int callchain_trace(struct stackframe *frame, void *data)
+{
+	struct perf_callchain_entry *entry = data;
+
+	perf_callchain_store(entry, frame->pc);
+	return 0;
+}
+
+void perf_callchain_kernel(struct perf_callchain_entry *entry,
+			   struct pt_regs *regs)
+{
+	xtensa_backtrace_kernel(regs, PERF_MAX_STACK_DEPTH,
+				callchain_trace, NULL, entry);
+}
+
+void perf_callchain_user(struct perf_callchain_entry *entry,
+			 struct pt_regs *regs)
+{
+	xtensa_backtrace_user(regs, PERF_MAX_STACK_DEPTH,
+			      callchain_trace, entry);
+}
+
+void perf_event_print_debug(void)
+{
+	unsigned long flags;
+	unsigned i;
+
+	local_irq_save(flags);
+	pr_info("CPU#%d: PMG: 0x%08lx\n", smp_processor_id(),
+		get_er(XTENSA_PMU_PMG));
+	for (i = 0; i < XCHAL_NUM_PERF_COUNTERS; ++i)
+		pr_info("PM%d: 0x%08lx, PMCTRL%d: 0x%08lx, PMSTAT%d: 0x%08lx\n",
+			i, get_er(XTENSA_PMU_PM(i)),
+			i, get_er(XTENSA_PMU_PMCTRL(i)),
+			i, get_er(XTENSA_PMU_PMSTAT(i)));
+	local_irq_restore(flags);
+}
+
+static irqreturn_t xtensa_pmu_irq_handler(int irq, void *dev_id)
+{
+	irqreturn_t rc = IRQ_NONE;
+	struct xtensa_pmu_events *ev = this_cpu_ptr(&xtensa_pmu_events);
+	unsigned i;
+
+	for (i = find_first_bit(ev->used_mask, XCHAL_NUM_PERF_COUNTERS);
+	     i < XCHAL_NUM_PERF_COUNTERS;
+	     i = find_next_bit(ev->used_mask, XCHAL_NUM_PERF_COUNTERS, i + 1)) {
+		uint32_t v = get_er(XTENSA_PMU_PMSTAT(i));
+		struct perf_event *event = ev->event[i];
+		struct hw_perf_event *hwc = &event->hw;
+		u64 last_period;
+
+		if (!(v & XTENSA_PMU_PMSTAT_OVFL))
+			continue;
+
+		set_er(v, XTENSA_PMU_PMSTAT(i));
+		xtensa_perf_event_update(event, hwc, i);
+		last_period = hwc->last_period;
+		if (xtensa_perf_event_set_period(event, hwc, i)) {
+			struct perf_sample_data data;
+			struct pt_regs *regs = get_irq_regs();
+
+			perf_sample_data_init(&data, 0, last_period);
+			if (perf_event_overflow(event, &data, regs))
+				xtensa_pmu_stop(event, 0);
+		}
+
+		rc = IRQ_HANDLED;
+	}
+	return rc;
+}
+
+static struct pmu xtensa_pmu = {
+	.pmu_enable = xtensa_pmu_enable,
+	.pmu_disable = xtensa_pmu_disable,
+	.event_init = xtensa_pmu_event_init,
+	.add = xtensa_pmu_add,
+	.del = xtensa_pmu_del,
+	.start = xtensa_pmu_start,
+	.stop = xtensa_pmu_stop,
+	.read = xtensa_pmu_read,
+};
+
+static void xtensa_pmu_setup(void)
+{
+	unsigned i;
+
+	set_er(0, XTENSA_PMU_PMG);
+	for (i = 0; i < XCHAL_NUM_PERF_COUNTERS; ++i) {
+		set_er(0, XTENSA_PMU_PMCTRL(i));
+		set_er(get_er(XTENSA_PMU_PMSTAT(i)), XTENSA_PMU_PMSTAT(i));
+	}
+}
+
+static int xtensa_pmu_notifier(struct notifier_block *self,
+			       unsigned long action, void *data)
+{
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_STARTING:
+		xtensa_pmu_setup();
+		break;
+
+	default:
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static int __init xtensa_pmu_init(void)
+{
+	int ret;
+	int irq = irq_create_mapping(NULL, XCHAL_PROFILING_INTERRUPT);
+
+	perf_cpu_notifier(xtensa_pmu_notifier);
+	ret = request_irq(irq, xtensa_pmu_irq_handler, IRQF_PERCPU,
+			  "pmu", NULL);
+	if (ret < 0)
+		return ret;
+
+	ret = perf_pmu_register(&xtensa_pmu, "cpu", PERF_TYPE_RAW);
+	if (ret)
+		free_irq(irq, NULL);
+
+	return ret;
+}
+early_initcall(xtensa_pmu_init);