8xx-pmu.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Performance event support - PPC 8xx
 *
 * Copyright 2016 Christophe Leroy, CS Systemes d'Information
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/perf_event.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <asm/pmc.h>
#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/ptrace.h>
#include <asm/text-patching.h>
#include <asm/inst.h>

#define PERF_8xx_ID_CPU_CYCLES		1
#define PERF_8xx_ID_HW_INSTRUCTIONS	2
#define PERF_8xx_ID_ITLB_LOAD_MISS	3
#define PERF_8xx_ID_DTLB_LOAD_MISS	4

#define C(x)	PERF_COUNT_HW_CACHE_##x
#define DTLB_LOAD_MISS	(C(DTLB) | (C(OP_READ) << 8) | (C(RESULT_MISS) << 16))
#define ITLB_LOAD_MISS	(C(ITLB) | (C(OP_READ) << 8) | (C(RESULT_MISS) << 16))

extern unsigned long itlb_miss_counter, dtlb_miss_counter;
extern atomic_t instruction_counter;

static atomic_t insn_ctr_ref;
static atomic_t itlb_miss_ref;
static atomic_t dtlb_miss_ref;

static s64 get_insn_ctr(void)
{
	int ctr;
	unsigned long counta;

	do {
		ctr = atomic_read(&instruction_counter);
		counta = mfspr(SPRN_COUNTA);
	} while (ctr != atomic_read(&instruction_counter));

	return ((s64)ctr << 16) | (counta >> 16);
}

static int event_type(struct perf_event *event)
{
	switch (event->attr.type) {
	case PERF_TYPE_HARDWARE:
		if (event->attr.config == PERF_COUNT_HW_CPU_CYCLES)
			return PERF_8xx_ID_CPU_CYCLES;
		if (event->attr.config == PERF_COUNT_HW_INSTRUCTIONS)
			return PERF_8xx_ID_HW_INSTRUCTIONS;
		break;
	case PERF_TYPE_HW_CACHE:
		if (event->attr.config == ITLB_LOAD_MISS)
			return PERF_8xx_ID_ITLB_LOAD_MISS;
		if (event->attr.config == DTLB_LOAD_MISS)
			return PERF_8xx_ID_DTLB_LOAD_MISS;
		break;
	case PERF_TYPE_RAW:
		break;
	default:
		return -ENOENT;
	}
	return -EOPNOTSUPP;
}

static int mpc8xx_pmu_event_init(struct perf_event *event)
{
	int type = event_type(event);

	if (type < 0)
		return type;
	return 0;
}

static int mpc8xx_pmu_add(struct perf_event *event, int flags)
{
	int type = event_type(event);
	s64 val = 0;

	if (type < 0)
		return type;

	switch (type) {
	case PERF_8xx_ID_CPU_CYCLES:
		val = get_tb();
		break;
	case PERF_8xx_ID_HW_INSTRUCTIONS:
		if (atomic_inc_return(&insn_ctr_ref) == 1)
			mtspr(SPRN_ICTRL, 0xc0080007);
		val = get_insn_ctr();
		break;
	case PERF_8xx_ID_ITLB_LOAD_MISS:
		if (atomic_inc_return(&itlb_miss_ref) == 1) {
			unsigned long target = patch_site_addr(&patch__itlbmiss_perf);

			patch_branch_site(&patch__itlbmiss_exit_1, target, 0);
		}
		val = itlb_miss_counter;
		break;
	case PERF_8xx_ID_DTLB_LOAD_MISS:
		if (atomic_inc_return(&dtlb_miss_ref) == 1) {
			unsigned long target = patch_site_addr(&patch__dtlbmiss_perf);

			patch_branch_site(&patch__dtlbmiss_exit_1, target, 0);
		}
		val = dtlb_miss_counter;
		break;
	}
	local64_set(&event->hw.prev_count, val);
	return 0;
}

static void mpc8xx_pmu_read(struct perf_event *event)
{
	int type = event_type(event);
	s64 prev, val = 0, delta = 0;

	if (type < 0)
		return;

	do {
		prev = local64_read(&event->hw.prev_count);
		switch (type) {
		case PERF_8xx_ID_CPU_CYCLES:
			val = get_tb();
			delta = 16 * (val - prev);
			break;
		case PERF_8xx_ID_HW_INSTRUCTIONS:
			val = get_insn_ctr();
			delta = prev - val;
			if (delta < 0)
				delta += 0x1000000000000LL;
			break;
		case PERF_8xx_ID_ITLB_LOAD_MISS:
			val = itlb_miss_counter;
			delta = (s64)((s32)val - (s32)prev);
			break;
		case PERF_8xx_ID_DTLB_LOAD_MISS:
			val = dtlb_miss_counter;
			delta = (s64)((s32)val - (s32)prev);
			break;
		}
	} while (local64_cmpxchg(&event->hw.prev_count, prev, val) != prev);

	local64_add(delta, &event->count);
}

static void mpc8xx_pmu_del(struct perf_event *event, int flags)
{
	ppc_inst_t insn = ppc_inst(PPC_RAW_MFSPR(10, SPRN_SPRG_SCRATCH2));

	mpc8xx_pmu_read(event);

	/* If it was the last user, stop counting to avoid useless overhead */
	switch (event_type(event)) {
	case PERF_8xx_ID_CPU_CYCLES:
		break;
	case PERF_8xx_ID_HW_INSTRUCTIONS:
		if (atomic_dec_return(&insn_ctr_ref) == 0)
			mtspr(SPRN_ICTRL, 7);
		break;
	case PERF_8xx_ID_ITLB_LOAD_MISS:
		if (atomic_dec_return(&itlb_miss_ref) == 0)
			patch_instruction_site(&patch__itlbmiss_exit_1, insn);
		break;
	case PERF_8xx_ID_DTLB_LOAD_MISS:
		if (atomic_dec_return(&dtlb_miss_ref) == 0)
			patch_instruction_site(&patch__dtlbmiss_exit_1, insn);
		break;
	}
}

static struct pmu mpc8xx_pmu = {
	.event_init	= mpc8xx_pmu_event_init,
	.add		= mpc8xx_pmu_add,
	.del		= mpc8xx_pmu_del,
	.read		= mpc8xx_pmu_read,
	.capabilities	= PERF_PMU_CAP_NO_INTERRUPT |
			  PERF_PMU_CAP_NO_NMI,
};

static int init_mpc8xx_pmu(void)
{
	mtspr(SPRN_ICTRL, 7);
	mtspr(SPRN_CMPA, 0);
	mtspr(SPRN_COUNTA, 0xffff);

	return perf_pmu_register(&mpc8xx_pmu, "cpu", PERF_TYPE_RAW);
}

early_initcall(init_mpc8xx_pmu);