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 
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 */
35 static int pmu_legacy_event_map(struct perf_event *event, u64 *config)
36 {
37 	return pmu_legacy_ctr_get_idx(event);
38 }
39 
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 
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  */
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 
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 
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 
139 void riscv_pmu_legacy_skip_init(void)
140 {
141 	pmu_init_done = true;
142 }
143