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/cpumask.h>
12#include <linux/irq.h>
13#include <linux/irqdesc.h>
14#include <linux/perf/riscv_pmu.h>
15#include <linux/printk.h>
16#include <linux/smp.h>
17#include <linux/sched_clock.h>
18
19#include <asm/sbi.h>
20
21static bool riscv_perf_user_access(struct perf_event *event)
22{
23	return ((event->attr.type == PERF_TYPE_HARDWARE) ||
24		(event->attr.type == PERF_TYPE_HW_CACHE) ||
25		(event->attr.type == PERF_TYPE_RAW)) &&
26		!!(event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT) &&
27		(event->hw.idx != -1);
28}
29
30void arch_perf_update_userpage(struct perf_event *event,
31			       struct perf_event_mmap_page *userpg, u64 now)
32{
33	struct clock_read_data *rd;
34	unsigned int seq;
35	u64 ns;
36
37	userpg->cap_user_time = 0;
38	userpg->cap_user_time_zero = 0;
39	userpg->cap_user_time_short = 0;
40	userpg->cap_user_rdpmc = riscv_perf_user_access(event);
41
42#ifdef CONFIG_RISCV_PMU
43	/*
44	 * The counters are 64-bit but the priv spec doesn't mandate all the
45	 * bits to be implemented: that's why, counter width can vary based on
46	 * the cpu vendor.
47	 */
48	if (userpg->cap_user_rdpmc)
49		userpg->pmc_width = to_riscv_pmu(event->pmu)->ctr_get_width(event->hw.idx) + 1;
50#endif
51
52	do {
53		rd = sched_clock_read_begin(&seq);
54
55		userpg->time_mult = rd->mult;
56		userpg->time_shift = rd->shift;
57		userpg->time_zero = rd->epoch_ns;
58		userpg->time_cycles = rd->epoch_cyc;
59		userpg->time_mask = rd->sched_clock_mask;
60
61		/*
62		 * Subtract the cycle base, such that software that
63		 * doesn't know about cap_user_time_short still 'works'
64		 * assuming no wraps.
65		 */
66		ns = mul_u64_u32_shr(rd->epoch_cyc, rd->mult, rd->shift);
67		userpg->time_zero -= ns;
68
69	} while (sched_clock_read_retry(seq));
70
71	userpg->time_offset = userpg->time_zero - now;
72
73	/*
74	 * time_shift is not expected to be greater than 31 due to
75	 * the original published conversion algorithm shifting a
76	 * 32-bit value (now specifies a 64-bit value) - refer
77	 * perf_event_mmap_page documentation in perf_event.h.
78	 */
79	if (userpg->time_shift == 32) {
80		userpg->time_shift = 31;
81		userpg->time_mult >>= 1;
82	}
83
84	/*
85	 * Internal timekeeping for enabled/running/stopped times
86	 * is always computed with the sched_clock.
87	 */
88	userpg->cap_user_time = 1;
89	userpg->cap_user_time_zero = 1;
90	userpg->cap_user_time_short = 1;
91}
92
93static unsigned long csr_read_num(int csr_num)
94{
95#define switchcase_csr_read(__csr_num, __val)		{\
96	case __csr_num:					\
97		__val = csr_read(__csr_num);		\
98		break; }
99#define switchcase_csr_read_2(__csr_num, __val)		{\
100	switchcase_csr_read(__csr_num + 0, __val)	 \
101	switchcase_csr_read(__csr_num + 1, __val)}
102#define switchcase_csr_read_4(__csr_num, __val)		{\
103	switchcase_csr_read_2(__csr_num + 0, __val)	 \
104	switchcase_csr_read_2(__csr_num + 2, __val)}
105#define switchcase_csr_read_8(__csr_num, __val)		{\
106	switchcase_csr_read_4(__csr_num + 0, __val)	 \
107	switchcase_csr_read_4(__csr_num + 4, __val)}
108#define switchcase_csr_read_16(__csr_num, __val)	{\
109	switchcase_csr_read_8(__csr_num + 0, __val)	 \
110	switchcase_csr_read_8(__csr_num + 8, __val)}
111#define switchcase_csr_read_32(__csr_num, __val)	{\
112	switchcase_csr_read_16(__csr_num + 0, __val)	 \
113	switchcase_csr_read_16(__csr_num + 16, __val)}
114
115	unsigned long ret = 0;
116
117	switch (csr_num) {
118	switchcase_csr_read_32(CSR_CYCLE, ret)
119	switchcase_csr_read_32(CSR_CYCLEH, ret)
120	default :
121		break;
122	}
123
124	return ret;
125#undef switchcase_csr_read_32
126#undef switchcase_csr_read_16
127#undef switchcase_csr_read_8
128#undef switchcase_csr_read_4
129#undef switchcase_csr_read_2
130#undef switchcase_csr_read
131}
132
133/*
134 * Read the CSR of a corresponding counter.
135 */
136unsigned long riscv_pmu_ctr_read_csr(unsigned long csr)
137{
138	if (csr < CSR_CYCLE || csr > CSR_HPMCOUNTER31H ||
139	   (csr > CSR_HPMCOUNTER31 && csr < CSR_CYCLEH)) {
140		pr_err("Invalid performance counter csr %lx\n", csr);
141		return -EINVAL;
142	}
143
144	return csr_read_num(csr);
145}
146
147u64 riscv_pmu_ctr_get_width_mask(struct perf_event *event)
148{
149	int cwidth;
150	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
151	struct hw_perf_event *hwc = &event->hw;
152
153	if (hwc->idx == -1)
154		/* Handle init case where idx is not initialized yet */
155		cwidth = rvpmu->ctr_get_width(0);
156	else
157		cwidth = rvpmu->ctr_get_width(hwc->idx);
158
159	return GENMASK_ULL(cwidth, 0);
160}
161
162u64 riscv_pmu_event_update(struct perf_event *event)
163{
164	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
165	struct hw_perf_event *hwc = &event->hw;
166	u64 prev_raw_count, new_raw_count;
167	unsigned long cmask;
168	u64 oldval, delta;
169
170	if (!rvpmu->ctr_read)
171		return 0;
172
173	cmask = riscv_pmu_ctr_get_width_mask(event);
174
175	do {
176		prev_raw_count = local64_read(&hwc->prev_count);
177		new_raw_count = rvpmu->ctr_read(event);
178		oldval = local64_cmpxchg(&hwc->prev_count, prev_raw_count,
179					 new_raw_count);
180	} while (oldval != prev_raw_count);
181
182	delta = (new_raw_count - prev_raw_count) & cmask;
183	local64_add(delta, &event->count);
184	local64_sub(delta, &hwc->period_left);
185
186	return delta;
187}
188
189void riscv_pmu_stop(struct perf_event *event, int flags)
190{
191	struct hw_perf_event *hwc = &event->hw;
192	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
193
194	WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
195
196	if (!(hwc->state & PERF_HES_STOPPED)) {
197		if (rvpmu->ctr_stop) {
198			rvpmu->ctr_stop(event, 0);
199			hwc->state |= PERF_HES_STOPPED;
200		}
201		riscv_pmu_event_update(event);
202		hwc->state |= PERF_HES_UPTODATE;
203	}
204}
205
206int riscv_pmu_event_set_period(struct perf_event *event)
207{
208	struct hw_perf_event *hwc = &event->hw;
209	s64 left = local64_read(&hwc->period_left);
210	s64 period = hwc->sample_period;
211	int overflow = 0;
212	uint64_t max_period = riscv_pmu_ctr_get_width_mask(event);
213
214	if (unlikely(left <= -period)) {
215		left = period;
216		local64_set(&hwc->period_left, left);
217		hwc->last_period = period;
218		overflow = 1;
219	}
220
221	if (unlikely(left <= 0)) {
222		left += period;
223		local64_set(&hwc->period_left, left);
224		hwc->last_period = period;
225		overflow = 1;
226	}
227
228	/*
229	 * Limit the maximum period to prevent the counter value
230	 * from overtaking the one we are about to program. In
231	 * effect we are reducing max_period to account for
232	 * interrupt latency (and we are being very conservative).
233	 */
234	if (left > (max_period >> 1))
235		left = (max_period >> 1);
236
237	local64_set(&hwc->prev_count, (u64)-left);
238
239	perf_event_update_userpage(event);
240
241	return overflow;
242}
243
244void riscv_pmu_start(struct perf_event *event, int flags)
245{
246	struct hw_perf_event *hwc = &event->hw;
247	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
248	uint64_t max_period = riscv_pmu_ctr_get_width_mask(event);
249	u64 init_val;
250
251	if (flags & PERF_EF_RELOAD)
252		WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
253
254	hwc->state = 0;
255	riscv_pmu_event_set_period(event);
256	init_val = local64_read(&hwc->prev_count) & max_period;
257	rvpmu->ctr_start(event, init_val);
258	perf_event_update_userpage(event);
259}
260
261static int riscv_pmu_add(struct perf_event *event, int flags)
262{
263	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
264	struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
265	struct hw_perf_event *hwc = &event->hw;
266	int idx;
267
268	idx = rvpmu->ctr_get_idx(event);
269	if (idx < 0)
270		return idx;
271
272	hwc->idx = idx;
273	cpuc->events[idx] = event;
274	cpuc->n_events++;
275	hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
276	if (flags & PERF_EF_START)
277		riscv_pmu_start(event, PERF_EF_RELOAD);
278
279	/* Propagate our changes to the userspace mapping. */
280	perf_event_update_userpage(event);
281
282	return 0;
283}
284
285static void riscv_pmu_del(struct perf_event *event, int flags)
286{
287	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
288	struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
289	struct hw_perf_event *hwc = &event->hw;
290
291	riscv_pmu_stop(event, PERF_EF_UPDATE);
292	cpuc->events[hwc->idx] = NULL;
293	/* The firmware need to reset the counter mapping */
294	if (rvpmu->ctr_stop)
295		rvpmu->ctr_stop(event, RISCV_PMU_STOP_FLAG_RESET);
296	cpuc->n_events--;
297	if (rvpmu->ctr_clear_idx)
298		rvpmu->ctr_clear_idx(event);
299	perf_event_update_userpage(event);
300	hwc->idx = -1;
301}
302
303static void riscv_pmu_read(struct perf_event *event)
304{
305	riscv_pmu_event_update(event);
306}
307
308static int riscv_pmu_event_init(struct perf_event *event)
309{
310	struct hw_perf_event *hwc = &event->hw;
311	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
312	int mapped_event;
313	u64 event_config = 0;
314	uint64_t cmask;
315
316	/* driver does not support branch stack sampling */
317	if (has_branch_stack(event))
318		return -EOPNOTSUPP;
319
320	hwc->flags = 0;
321	mapped_event = rvpmu->event_map(event, &event_config);
322	if (mapped_event < 0) {
323		pr_debug("event %x:%llx not supported\n", event->attr.type,
324			 event->attr.config);
325		return mapped_event;
326	}
327
328	/*
329	 * idx is set to -1 because the index of a general event should not be
330	 * decided until binding to some counter in pmu->add().
331	 * config will contain the information about counter CSR
332	 * the idx will contain the counter index
333	 */
334	hwc->config = event_config;
335	hwc->idx = -1;
336	hwc->event_base = mapped_event;
337
338	if (rvpmu->event_init)
339		rvpmu->event_init(event);
340
341	if (!is_sampling_event(event)) {
342		/*
343		 * For non-sampling runs, limit the sample_period to half
344		 * of the counter width. That way, the new counter value
345		 * is far less likely to overtake the previous one unless
346		 * you have some serious IRQ latency issues.
347		 */
348		cmask = riscv_pmu_ctr_get_width_mask(event);
349		hwc->sample_period  =  cmask >> 1;
350		hwc->last_period    = hwc->sample_period;
351		local64_set(&hwc->period_left, hwc->sample_period);
352	}
353
354	return 0;
355}
356
357static int riscv_pmu_event_idx(struct perf_event *event)
358{
359	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
360
361	if (!(event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT))
362		return 0;
363
364	if (rvpmu->csr_index)
365		return rvpmu->csr_index(event) + 1;
366
367	return 0;
368}
369
370static void riscv_pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)
371{
372	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
373
374	if (rvpmu->event_mapped) {
375		rvpmu->event_mapped(event, mm);
376		perf_event_update_userpage(event);
377	}
378}
379
380static void riscv_pmu_event_unmapped(struct perf_event *event, struct mm_struct *mm)
381{
382	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
383
384	if (rvpmu->event_unmapped) {
385		rvpmu->event_unmapped(event, mm);
386		perf_event_update_userpage(event);
387	}
388}
389
390struct riscv_pmu *riscv_pmu_alloc(void)
391{
392	struct riscv_pmu *pmu;
393	int cpuid, i;
394	struct cpu_hw_events *cpuc;
395
396	pmu = kzalloc(sizeof(*pmu), GFP_KERNEL);
397	if (!pmu)
398		goto out;
399
400	pmu->hw_events = alloc_percpu_gfp(struct cpu_hw_events, GFP_KERNEL);
401	if (!pmu->hw_events) {
402		pr_info("failed to allocate per-cpu PMU data.\n");
403		goto out_free_pmu;
404	}
405
406	for_each_possible_cpu(cpuid) {
407		cpuc = per_cpu_ptr(pmu->hw_events, cpuid);
408		cpuc->n_events = 0;
409		for (i = 0; i < RISCV_MAX_COUNTERS; i++)
410			cpuc->events[i] = NULL;
411	}
412	pmu->pmu = (struct pmu) {
413		.event_init	= riscv_pmu_event_init,
414		.event_mapped	= riscv_pmu_event_mapped,
415		.event_unmapped	= riscv_pmu_event_unmapped,
416		.event_idx	= riscv_pmu_event_idx,
417		.add		= riscv_pmu_add,
418		.del		= riscv_pmu_del,
419		.start		= riscv_pmu_start,
420		.stop		= riscv_pmu_stop,
421		.read		= riscv_pmu_read,
422	};
423
424	return pmu;
425
426out_free_pmu:
427	kfree(pmu);
428out:
429	return NULL;
430}
431