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