1// SPDX-License-Identifier: GPL-2.0
2/*
3 * RISC-V performance counter support.
4 *
5 * Copyright (C) 2021 Western Digital Corporation or its affiliates.
6 *
7 * This implementation is based on old RISC-V perf and ARM perf event code
8 * which are in turn based on sparc64 and x86 code.
9 */
10
11#include <linux/mod_devicetable.h>
12#include <linux/perf/riscv_pmu.h>
13#include <linux/platform_device.h>
14
15#define RISCV_PMU_LEGACY_CYCLE 0
16#define RISCV_PMU_LEGACY_INSTRET 2
17
18static bool pmu_init_done;
19
20static int pmu_legacy_ctr_get_idx(struct perf_event *event)
21{
22 struct perf_event_attr *attr = &event->attr;
23
24 if (event->attr.type != PERF_TYPE_HARDWARE)
25 return -EOPNOTSUPP;
26 if (attr->config == PERF_COUNT_HW_CPU_CYCLES)
27 return RISCV_PMU_LEGACY_CYCLE;
28 else if (attr->config == PERF_COUNT_HW_INSTRUCTIONS)
29 return RISCV_PMU_LEGACY_INSTRET;
30 else
31 return -EOPNOTSUPP;
32}
33
34/* For legacy config & counter index are same */
35static int pmu_legacy_event_map(struct perf_event *event, u64 *config)
36{
37 return pmu_legacy_ctr_get_idx(event);
38}
39
40/* cycle & instret are always 64 bit, one bit less according to SBI spec */
41static int pmu_legacy_ctr_get_width(int idx)
42{
43 return 63;
44}
45
46static u64 pmu_legacy_read_ctr(struct perf_event *event)
47{
48 struct hw_perf_event *hwc = &event->hw;
49 int idx = hwc->idx;
50 u64 val;
51
52 if (idx == RISCV_PMU_LEGACY_CYCLE) {
53 val = riscv_pmu_ctr_read_csr(CSR_CYCLE);
54 if (IS_ENABLED(CONFIG_32BIT))
55 val = (u64)riscv_pmu_ctr_read_csr(CSR_CYCLEH) << 32 | val;
56 } else if (idx == RISCV_PMU_LEGACY_INSTRET) {
57 val = riscv_pmu_ctr_read_csr(CSR_INSTRET);
58 if (IS_ENABLED(CONFIG_32BIT))
59 val = ((u64)riscv_pmu_ctr_read_csr(CSR_INSTRETH)) << 32 | val;
60 } else
61 return 0;
62
63 return val;
64}
65
66static void pmu_legacy_ctr_start(struct perf_event *event, u64 ival)
67{
68 struct hw_perf_event *hwc = &event->hw;
69 u64 initial_val = pmu_legacy_read_ctr(event);
70
71 /**
72 * The legacy method doesn't really have a start/stop method.
73 * It also can not update the counter with a initial value.
74 * But we still need to set the prev_count so that read() can compute
75 * the delta. Just use the current counter value to set the prev_count.
76 */
77 local64_set(&hwc->prev_count, initial_val);
78}
79
80static uint8_t pmu_legacy_csr_index(struct perf_event *event)
81{
82 return event->hw.idx;
83}
84
85static void pmu_legacy_event_mapped(struct perf_event *event, struct mm_struct *mm)
86{
87 if (event->attr.config != PERF_COUNT_HW_CPU_CYCLES &&
88 event->attr.config != PERF_COUNT_HW_INSTRUCTIONS)
89 return;
90
91 event->hw.flags |= PERF_EVENT_FLAG_USER_READ_CNT;
92}
93
94static void pmu_legacy_event_unmapped(struct perf_event *event, struct mm_struct *mm)
95{
96 if (event->attr.config != PERF_COUNT_HW_CPU_CYCLES &&
97 event->attr.config != PERF_COUNT_HW_INSTRUCTIONS)
98 return;
99
100 event->hw.flags &= ~PERF_EVENT_FLAG_USER_READ_CNT;
101}
102
103/*
104 * This is just a simple implementation to allow legacy implementations
105 * compatible with new RISC-V PMU driver framework.
106 * This driver only allows reading two counters i.e CYCLE & INSTRET.
107 * However, it can not start or stop the counter. Thus, it is not very useful
108 * will be removed in future.
109 */
110static void pmu_legacy_init(struct riscv_pmu *pmu)
111{
112 pr_info("Legacy PMU implementation is available\n");
113
114 pmu->cmask = BIT(RISCV_PMU_LEGACY_CYCLE) |
115 BIT(RISCV_PMU_LEGACY_INSTRET);
116 pmu->ctr_start = pmu_legacy_ctr_start;
117 pmu->ctr_stop = NULL;
118 pmu->event_map = pmu_legacy_event_map;
119 pmu->ctr_get_idx = pmu_legacy_ctr_get_idx;
120 pmu->ctr_get_width = pmu_legacy_ctr_get_width;
121 pmu->ctr_clear_idx = NULL;
122 pmu->ctr_read = pmu_legacy_read_ctr;
123 pmu->event_mapped = pmu_legacy_event_mapped;
124 pmu->event_unmapped = pmu_legacy_event_unmapped;
125 pmu->csr_index = pmu_legacy_csr_index;
126 pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;
127 pmu->pmu.capabilities |= PERF_PMU_CAP_NO_EXCLUDE;
128
129 perf_pmu_register(pmu: &pmu->pmu, name: "cpu", type: PERF_TYPE_RAW);
130}
131
132static int pmu_legacy_device_probe(struct platform_device *pdev)
133{
134 struct riscv_pmu *pmu = NULL;
135
136 pmu = riscv_pmu_alloc();
137 if (!pmu)
138 return -ENOMEM;
139 pmu_legacy_init(pmu);
140
141 return 0;
142}
143
144static struct platform_driver pmu_legacy_driver = {
145 .probe = pmu_legacy_device_probe,
146 .driver = {
147 .name = RISCV_PMU_LEGACY_PDEV_NAME,
148 },
149};
150
151static int __init riscv_pmu_legacy_devinit(void)
152{
153 int ret;
154 struct platform_device *pdev;
155
156 if (likely(pmu_init_done))
157 return 0;
158
159 ret = platform_driver_register(&pmu_legacy_driver);
160 if (ret)
161 return ret;
162
163 pdev = platform_device_register_simple(name: RISCV_PMU_LEGACY_PDEV_NAME, id: -1, NULL, num: 0);
164 if (IS_ERR(ptr: pdev)) {
165 platform_driver_unregister(&pmu_legacy_driver);
166 return PTR_ERR(ptr: pdev);
167 }
168
169 return ret;
170}
171late_initcall(riscv_pmu_legacy_devinit);
172
173void riscv_pmu_legacy_skip_init(void)
174{
175 pmu_init_done = true;
176}
177

source code of linux/drivers/perf/riscv_pmu_legacy.c