drivers/perf/riscv_pmu.c

   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
  18 #include <asm/sbi.h>
  19
  20 static unsigned long csr_read_num(int csr_num)
  21 {
  22 #define switchcase_csr_read(__csr_num, __val)           {\
  23         case __csr_num:                                 \
  24                 __val = csr_read(__csr_num);            \
  25                 break; }
  26 #define switchcase_csr_read_2(__csr_num, __val)         {\
  27         switchcase_csr_read(__csr_num + 0, __val)        \
  28         switchcase_csr_read(__csr_num + 1, __val)}
  29 #define switchcase_csr_read_4(__csr_num, __val)         {\
  30         switchcase_csr_read_2(__csr_num + 0, __val)      \
  31         switchcase_csr_read_2(__csr_num + 2, __val)}
  32 #define switchcase_csr_read_8(__csr_num, __val)         {\
  33         switchcase_csr_read_4(__csr_num + 0, __val)      \
  34         switchcase_csr_read_4(__csr_num + 4, __val)}
  35 #define switchcase_csr_read_16(__csr_num, __val)        {\
  36         switchcase_csr_read_8(__csr_num + 0, __val)      \
  37         switchcase_csr_read_8(__csr_num + 8, __val)}
  38 #define switchcase_csr_read_32(__csr_num, __val)        {\
  39         switchcase_csr_read_16(__csr_num + 0, __val)     \
  40         switchcase_csr_read_16(__csr_num + 16, __val)}
  41
  42         unsigned long ret = 0;
  43
  44         switch (csr_num) {
  45         switchcase_csr_read_32(CSR_CYCLE, ret)
  46         switchcase_csr_read_32(CSR_CYCLEH, ret)
  47         default :
  48                 break;
  49         }
  50
  51         return ret;
  52 #undef switchcase_csr_read_32
  53 #undef switchcase_csr_read_16
  54 #undef switchcase_csr_read_8
  55 #undef switchcase_csr_read_4
  56 #undef switchcase_csr_read_2
  57 #undef switchcase_csr_read
  58 }
  59
  60 /*
  61  * Read the CSR of a corresponding counter.
  62  */
  63 unsigned long riscv_pmu_ctr_read_csr(unsigned long csr)
  64 {
  65         if (csr < CSR_CYCLE || csr > CSR_HPMCOUNTER31H ||
  66            (csr > CSR_HPMCOUNTER31 && csr < CSR_CYCLEH)) {
  67                 pr_err("Invalid performance counter csr %lx\n", csr);
  68                 return -EINVAL;
  69         }
  70
  71         return csr_read_num(csr);
  72 }
  73
  74 u64 riscv_pmu_ctr_get_width_mask(struct perf_event *event)
  75 {
  76         int cwidth;
  77         struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
  78         struct hw_perf_event *hwc = &event->hw;
  79
  80         if (!rvpmu->ctr_get_width)
  81         /**
  82          * If the pmu driver doesn't support counter width, set it to default
  83          * maximum allowed by the specification.
  84          */
  85                 cwidth = 63;
  86         else {
  87                 if (hwc->idx == -1)
  88                         /* Handle init case where idx is not initialized yet */
  89                         cwidth = rvpmu->ctr_get_width(0);
  90                 else
  91                         cwidth = rvpmu->ctr_get_width(hwc->idx);
  92         }
  93
  94         return GENMASK_ULL(cwidth, 0);
  95 }
  96
  97 u64 riscv_pmu_event_update(struct perf_event *event)
  98 {
  99         struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
 100         struct hw_perf_event *hwc = &event->hw;
 101         u64 prev_raw_count, new_raw_count;
 102         unsigned long cmask;
 103         u64 oldval, delta;
 104
 105         if (!rvpmu->ctr_read)
 106                 return 0;
 107
 108         cmask = riscv_pmu_ctr_get_width_mask(event);
 109
 110         do {
 111                 prev_raw_count = local64_read(&hwc->prev_count);
 112                 new_raw_count = rvpmu->ctr_read(event);
 113                 oldval = local64_cmpxchg(&hwc->prev_count, prev_raw_count,
 114                                          new_raw_count);
 115         } while (oldval != prev_raw_count);
 116
 117         delta = (new_raw_count - prev_raw_count) & cmask;
 118         local64_add(delta, &event->count);
 119         local64_sub(delta, &hwc->period_left);
 120
 121         return delta;
 122 }
 123
 124 static void riscv_pmu_stop(struct perf_event *event, int flags)
 125 {
 126         struct hw_perf_event *hwc = &event->hw;
 127         struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
 128
 129         WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
 130
 131         if (!(hwc->state & PERF_HES_STOPPED)) {
 132                 if (rvpmu->ctr_stop) {
 133                         rvpmu->ctr_stop(event, 0);
 134                         hwc->state |= PERF_HES_STOPPED;
 135                 }
 136                 riscv_pmu_event_update(event);
 137                 hwc->state |= PERF_HES_UPTODATE;
 138         }
 139 }
 140
 141 int riscv_pmu_event_set_period(struct perf_event *event)
 142 {
 143         struct hw_perf_event *hwc = &event->hw;
 144         s64 left = local64_read(&hwc->period_left);
 145         s64 period = hwc->sample_period;
 146         int overflow = 0;
 147         uint64_t max_period = riscv_pmu_ctr_get_width_mask(event);
 148
 149         if (unlikely(left <= -period)) {
 150                 left = period;
 151                 local64_set(&hwc->period_left, left);
 152                 hwc->last_period = period;
 153                 overflow = 1;
 154         }
 155
 156         if (unlikely(left <= 0)) {
 157                 left += period;
 158                 local64_set(&hwc->period_left, left);
 159                 hwc->last_period = period;
 160                 overflow = 1;
 161         }
 162
 163         /*
 164          * Limit the maximum period to prevent the counter value
 165          * from overtaking the one we are about to program. In
 166          * effect we are reducing max_period to account for
 167          * interrupt latency (and we are being very conservative).
 168          */
 169         if (left > (max_period >> 1))
 170                 left = (max_period >> 1);
 171
 172         local64_set(&hwc->prev_count, (u64)-left);
 173         perf_event_update_userpage(event);
 174
 175         return overflow;
 176 }
 177
 178 static void riscv_pmu_start(struct perf_event *event, int flags)
 179 {
 180         struct hw_perf_event *hwc = &event->hw;
 181         struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
 182         uint64_t max_period = riscv_pmu_ctr_get_width_mask(event);
 183         u64 init_val;
 184
 185         if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
 186                 return;
 187
 188         if (flags & PERF_EF_RELOAD)
 189                 WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
 190
 191         hwc->state = 0;
 192         riscv_pmu_event_set_period(event);
 193         init_val = local64_read(&hwc->prev_count) & max_period;
 194         rvpmu->ctr_start(event, init_val);
 195         perf_event_update_userpage(event);
 196 }
 197
 198 static int riscv_pmu_add(struct perf_event *event, int flags)
 199 {
 200         struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
 201         struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
 202         struct hw_perf_event *hwc = &event->hw;
 203         int idx;
 204
 205         idx = rvpmu->ctr_get_idx(event);
 206         if (idx < 0)
 207                 return idx;
 208
 209         hwc->idx = idx;
 210         cpuc->events[idx] = event;
 211         cpuc->n_events++;
 212         hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
 213         if (flags & PERF_EF_START)
 214                 riscv_pmu_start(event, PERF_EF_RELOAD);
 215
 216         /* Propagate our changes to the userspace mapping. */
 217         perf_event_update_userpage(event);
 218
 219         return 0;
 220 }
 221
 222 static void riscv_pmu_del(struct perf_event *event, int flags)
 223 {
 224         struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
 225         struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
 226         struct hw_perf_event *hwc = &event->hw;
 227
 228         riscv_pmu_stop(event, PERF_EF_UPDATE);
 229         cpuc->events[hwc->idx] = NULL;
 230         /* The firmware need to reset the counter mapping */
 231         if (rvpmu->ctr_stop)
 232                 rvpmu->ctr_stop(event, RISCV_PMU_STOP_FLAG_RESET);
 233         cpuc->n_events--;
 234         if (rvpmu->ctr_clear_idx)
 235                 rvpmu->ctr_clear_idx(event);
 236         perf_event_update_userpage(event);
 237         hwc->idx = -1;
 238 }
 239
 240 static void riscv_pmu_read(struct perf_event *event)
 241 {
 242         riscv_pmu_event_update(event);
 243 }
 244
 245 static int riscv_pmu_event_init(struct perf_event *event)
 246 {
 247         struct hw_perf_event *hwc = &event->hw;
 248         struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
 249         int mapped_event;
 250         u64 event_config = 0;
 251         uint64_t cmask;
 252
 253         hwc->flags = 0;
 254         mapped_event = rvpmu->event_map(event, &event_config);
 255         if (mapped_event < 0) {
 256                 pr_debug("event %x:%llx not supported\n", event->attr.type,
 257                          event->attr.config);
 258                 return mapped_event;
 259         }
 260
 261         /*
 262          * idx is set to -1 because the index of a general event should not be
 263          * decided until binding to some counter in pmu->add().
 264          * config will contain the information about counter CSR
 265          * the idx will contain the counter index
 266          */
 267         hwc->config = event_config;
 268         hwc->idx = -1;
 269         hwc->event_base = mapped_event;
 270
 271         if (!is_sampling_event(event)) {
 272                 /*
 273                  * For non-sampling runs, limit the sample_period to half
 274                  * of the counter width. That way, the new counter value
 275                  * is far less likely to overtake the previous one unless
 276                  * you have some serious IRQ latency issues.
 277                  */
 278                 cmask = riscv_pmu_ctr_get_width_mask(event);
 279                 hwc->sample_period  =  cmask >> 1;
 280                 hwc->last_period    = hwc->sample_period;
 281                 local64_set(&hwc->period_left, hwc->sample_period);
 282         }
 283
 284         return 0;
 285 }
 286
 287 struct riscv_pmu *riscv_pmu_alloc(void)
 288 {
 289         struct riscv_pmu *pmu;
 290         int cpuid, i;
 291         struct cpu_hw_events *cpuc;
 292
 293         pmu = kzalloc(sizeof(*pmu), GFP_KERNEL);
 294         if (!pmu)
 295                 goto out;
 296
 297         pmu->hw_events = alloc_percpu_gfp(struct cpu_hw_events, GFP_KERNEL);
 298         if (!pmu->hw_events) {
 299                 pr_info("failed to allocate per-cpu PMU data.\n");
 300                 goto out_free_pmu;
 301         }
 302
 303         for_each_possible_cpu(cpuid) {
 304                 cpuc = per_cpu_ptr(pmu->hw_events, cpuid);
 305                 cpuc->n_events = 0;
 306                 for (i = 0; i < RISCV_MAX_COUNTERS; i++)
 307                         cpuc->events[i] = NULL;
 308         }
 309         pmu->pmu = (struct pmu) {
 310                 .event_init     = riscv_pmu_event_init,
 311                 .add            = riscv_pmu_add,
 312                 .del            = riscv_pmu_del,
 313                 .start          = riscv_pmu_start,
 314                 .stop           = riscv_pmu_stop,
 315                 .read           = riscv_pmu_read,
 316         };
 317
 318         return pmu;
 319
 320 out_free_pmu:
 321         kfree(pmu);
 322 out:
 323         return NULL;
 324 }