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 #define RISCV_PMU_LEGACY_NUM_CTR	2
18 
19 static bool pmu_init_done;
20 
21 static int pmu_legacy_ctr_get_idx(struct perf_event *event)
22 {
23 	struct perf_event_attr *attr = &event->attr;
24 
25 	if (event->attr.type != PERF_TYPE_HARDWARE)
26 		return -EOPNOTSUPP;
27 	if (attr->config == PERF_COUNT_HW_CPU_CYCLES)
28 		return RISCV_PMU_LEGACY_CYCLE;
29 	else if (attr->config == PERF_COUNT_HW_INSTRUCTIONS)
30 		return RISCV_PMU_LEGACY_INSTRET;
31 	else
32 		return -EOPNOTSUPP;
33 }
34 
35 /* For legacy config & counter index are same */
36 static int pmu_legacy_event_map(struct perf_event *event, u64 *config)
37 {
38 	return pmu_legacy_ctr_get_idx(event);
39 }
40 
41 static u64 pmu_legacy_read_ctr(struct perf_event *event)
42 {
43 	struct hw_perf_event *hwc = &event->hw;
44 	int idx = hwc->idx;
45 	u64 val;
46 
47 	if (idx == RISCV_PMU_LEGACY_CYCLE) {
48 		val = riscv_pmu_ctr_read_csr(CSR_CYCLE);
49 		if (IS_ENABLED(CONFIG_32BIT))
50 			val = (u64)riscv_pmu_ctr_read_csr(CSR_CYCLEH) << 32 | val;
51 	} else if (idx == RISCV_PMU_LEGACY_INSTRET) {
52 		val = riscv_pmu_ctr_read_csr(CSR_INSTRET);
53 		if (IS_ENABLED(CONFIG_32BIT))
54 			val = ((u64)riscv_pmu_ctr_read_csr(CSR_INSTRETH)) << 32 | val;
55 	} else
56 		return 0;
57 
58 	return val;
59 }
60 
61 static void pmu_legacy_ctr_start(struct perf_event *event, u64 ival)
62 {
63 	struct hw_perf_event *hwc = &event->hw;
64 	u64 initial_val = pmu_legacy_read_ctr(event);
65 
66 	/**
67 	 * The legacy method doesn't really have a start/stop method.
68 	 * It also can not update the counter with a initial value.
69 	 * But we still need to set the prev_count so that read() can compute
70 	 * the delta. Just use the current counter value to set the prev_count.
71 	 */
72 	local64_set(&hwc->prev_count, initial_val);
73 }
74 
75 /*
76  * This is just a simple implementation to allow legacy implementations
77  * compatible with new RISC-V PMU driver framework.
78  * This driver only allows reading two counters i.e CYCLE & INSTRET.
79  * However, it can not start or stop the counter. Thus, it is not very useful
80  * will be removed in future.
81  */
82 static void pmu_legacy_init(struct riscv_pmu *pmu)
83 {
84 	pr_info("Legacy PMU implementation is available\n");
85 
86 	pmu->num_counters = RISCV_PMU_LEGACY_NUM_CTR;
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