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 1
17
18 static bool pmu_init_done;
19
pmu_legacy_ctr_get_idx(struct perf_event * event)20 static 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 */
pmu_legacy_event_map(struct perf_event * event,u64 * config)35 static int pmu_legacy_event_map(struct perf_event *event, u64 *config)
36 {
37 return pmu_legacy_ctr_get_idx(event);
38 }
39
pmu_legacy_read_ctr(struct perf_event * event)40 static u64 pmu_legacy_read_ctr(struct perf_event *event)
41 {
42 struct hw_perf_event *hwc = &event->hw;
43 int idx = hwc->idx;
44 u64 val;
45
46 if (idx == RISCV_PMU_LEGACY_CYCLE) {
47 val = riscv_pmu_ctr_read_csr(CSR_CYCLE);
48 if (IS_ENABLED(CONFIG_32BIT))
49 val = (u64)riscv_pmu_ctr_read_csr(CSR_CYCLEH) << 32 | val;
50 } else if (idx == RISCV_PMU_LEGACY_INSTRET) {
51 val = riscv_pmu_ctr_read_csr(CSR_INSTRET);
52 if (IS_ENABLED(CONFIG_32BIT))
53 val = ((u64)riscv_pmu_ctr_read_csr(CSR_INSTRETH)) << 32 | val;
54 } else
55 return 0;
56
57 return val;
58 }
59
pmu_legacy_ctr_start(struct perf_event * event,u64 ival)60 static void pmu_legacy_ctr_start(struct perf_event *event, u64 ival)
61 {
62 struct hw_perf_event *hwc = &event->hw;
63 u64 initial_val = pmu_legacy_read_ctr(event);
64
65 /**
66 * The legacy method doesn't really have a start/stop method.
67 * It also can not update the counter with a initial value.
68 * But we still need to set the prev_count so that read() can compute
69 * the delta. Just use the current counter value to set the prev_count.
70 */
71 local64_set(&hwc->prev_count, initial_val);
72 }
73
74 /*
75 * This is just a simple implementation to allow legacy implementations
76 * compatible with new RISC-V PMU driver framework.
77 * This driver only allows reading two counters i.e CYCLE & INSTRET.
78 * However, it can not start or stop the counter. Thus, it is not very useful
79 * will be removed in future.
80 */
pmu_legacy_init(struct riscv_pmu * pmu)81 static void pmu_legacy_init(struct riscv_pmu *pmu)
82 {
83 pr_info("Legacy PMU implementation is available\n");
84
85 pmu->cmask = BIT(RISCV_PMU_LEGACY_CYCLE) |
86 BIT(RISCV_PMU_LEGACY_INSTRET);
87 pmu->ctr_start = pmu_legacy_ctr_start;
88 pmu->ctr_stop = NULL;
89 pmu->event_map = pmu_legacy_event_map;
90 pmu->ctr_get_idx = pmu_legacy_ctr_get_idx;
91 pmu->ctr_get_width = NULL;
92 pmu->ctr_clear_idx = NULL;
93 pmu->ctr_read = pmu_legacy_read_ctr;
94
95 perf_pmu_register(&pmu->pmu, "cpu", PERF_TYPE_RAW);
96 }
97
pmu_legacy_device_probe(struct platform_device * pdev)98 static int pmu_legacy_device_probe(struct platform_device *pdev)
99 {
100 struct riscv_pmu *pmu = NULL;
101
102 pmu = riscv_pmu_alloc();
103 if (!pmu)
104 return -ENOMEM;
105 pmu_legacy_init(pmu);
106
107 return 0;
108 }
109
110 static struct platform_driver pmu_legacy_driver = {
111 .probe = pmu_legacy_device_probe,
112 .driver = {
113 .name = RISCV_PMU_LEGACY_PDEV_NAME,
114 },
115 };
116
riscv_pmu_legacy_devinit(void)117 static int __init riscv_pmu_legacy_devinit(void)
118 {
119 int ret;
120 struct platform_device *pdev;
121
122 if (likely(pmu_init_done))
123 return 0;
124
125 ret = platform_driver_register(&pmu_legacy_driver);
126 if (ret)
127 return ret;
128
129 pdev = platform_device_register_simple(RISCV_PMU_LEGACY_PDEV_NAME, -1, NULL, 0);
130 if (IS_ERR(pdev)) {
131 platform_driver_unregister(&pmu_legacy_driver);
132 return PTR_ERR(pdev);
133 }
134
135 return ret;
136 }
137 late_initcall(riscv_pmu_legacy_devinit);
138
riscv_pmu_legacy_skip_init(void)139 void riscv_pmu_legacy_skip_init(void)
140 {
141 pmu_init_done = true;
142 }
143
