1 files changed, 320 insertions, 0 deletions
diff --git a/drivers/perf/riscv_pmu.c b/drivers/perf/riscv_pmu.c
new file mode 100644
index 000000000..56897d4d4
--- /dev/null
+++ b/drivers/perf/riscv_pmu.c
@@ -0,0 +1,320 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RISC-V performance counter support.
+ *
+ * Copyright (C) 2021 Western Digital Corporation or its affiliates.
+ *
+ * This implementation is based on old RISC-V perf and ARM perf event code
+ * which are in turn based on sparc64 and x86 code.
+ */
+
+#include <linux/cpumask.h>
+#include <linux/irq.h>
+#include <linux/irqdesc.h>
+#include <linux/perf/riscv_pmu.h>
+#include <linux/printk.h>
+#include <linux/smp.h>
+
+#include <asm/sbi.h>
+
+static unsigned long csr_read_num(int csr_num)
+{
+#define switchcase_csr_read(__csr_num, __val)		{\
+	case __csr_num:					\
+		__val = csr_read(__csr_num);		\
+		break; }
+#define switchcase_csr_read_2(__csr_num, __val)		{\
+	switchcase_csr_read(__csr_num + 0, __val)	 \
+	switchcase_csr_read(__csr_num + 1, __val)}
+#define switchcase_csr_read_4(__csr_num, __val)		{\
+	switchcase_csr_read_2(__csr_num + 0, __val)	 \
+	switchcase_csr_read_2(__csr_num + 2, __val)}
+#define switchcase_csr_read_8(__csr_num, __val)		{\
+	switchcase_csr_read_4(__csr_num + 0, __val)	 \
+	switchcase_csr_read_4(__csr_num + 4, __val)}
+#define switchcase_csr_read_16(__csr_num, __val)	{\
+	switchcase_csr_read_8(__csr_num + 0, __val)	 \
+	switchcase_csr_read_8(__csr_num + 8, __val)}
+#define switchcase_csr_read_32(__csr_num, __val)	{\
+	switchcase_csr_read_16(__csr_num + 0, __val)	 \
+	switchcase_csr_read_16(__csr_num + 16, __val)}
+
+	unsigned long ret = 0;
+
+	switch (csr_num) {
+	switchcase_csr_read_32(CSR_CYCLE, ret)
+	switchcase_csr_read_32(CSR_CYCLEH, ret)
+	default :
+		break;
+	}
+
+	return ret;
+#undef switchcase_csr_read_32
+#undef switchcase_csr_read_16
+#undef switchcase_csr_read_8
+#undef switchcase_csr_read_4
+#undef switchcase_csr_read_2
+#undef switchcase_csr_read
+}
+
+/*
+ * Read the CSR of a corresponding counter.
+ */
+unsigned long riscv_pmu_ctr_read_csr(unsigned long csr)
+{
+	if (csr < CSR_CYCLE || csr > CSR_HPMCOUNTER31H ||
+	   (csr > CSR_HPMCOUNTER31 && csr < CSR_CYCLEH)) {
+		pr_err("Invalid performance counter csr %lx\n", csr);
+		return -EINVAL;
+	}
+
+	return csr_read_num(csr);
+}
+
+u64 riscv_pmu_ctr_get_width_mask(struct perf_event *event)
+{
+	int cwidth;
+	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
+	struct hw_perf_event *hwc = &event->hw;
+
+	if (!rvpmu->ctr_get_width)
+	/**
+	 * If the pmu driver doesn't support counter width, set it to default
+	 * maximum allowed by the specification.
+	 */
+		cwidth = 63;
+	else {
+		if (hwc->idx == -1)
+			/* Handle init case where idx is not initialized yet */
+			cwidth = rvpmu->ctr_get_width(0);
+		else
+			cwidth = rvpmu->ctr_get_width(hwc->idx);
+	}
+
+	return GENMASK_ULL(cwidth, 0);
+}
+
+u64 riscv_pmu_event_update(struct perf_event *event)
+{
+	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
+	struct hw_perf_event *hwc = &event->hw;
+	u64 prev_raw_count, new_raw_count;
+	unsigned long cmask;
+	u64 oldval, delta;
+
+	if (!rvpmu->ctr_read)
+		return 0;
+
+	cmask = riscv_pmu_ctr_get_width_mask(event);
+
+	do {
+		prev_raw_count = local64_read(&hwc->prev_count);
+		new_raw_count = rvpmu->ctr_read(event);
+		oldval = local64_cmpxchg(&hwc->prev_count, prev_raw_count,
+					 new_raw_count);
+	} while (oldval != prev_raw_count);
+
+	delta = (new_raw_count - prev_raw_count) & cmask;
+	local64_add(delta, &event->count);
+	local64_sub(delta, &hwc->period_left);
+
+	return delta;
+}
+
+void riscv_pmu_stop(struct perf_event *event, int flags)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
+
+	WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
+
+	if (!(hwc->state & PERF_HES_STOPPED)) {
+		if (rvpmu->ctr_stop) {
+			rvpmu->ctr_stop(event, 0);
+			hwc->state |= PERF_HES_STOPPED;
+		}
+		riscv_pmu_event_update(event);
+		hwc->state |= PERF_HES_UPTODATE;
+	}
+}
+
+int riscv_pmu_event_set_period(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	s64 left = local64_read(&hwc->period_left);
+	s64 period = hwc->sample_period;
+	int overflow = 0;
+	uint64_t max_period = riscv_pmu_ctr_get_width_mask(event);
+
+	if (unlikely(left <= -period)) {
+		left = period;
+		local64_set(&hwc->period_left, left);
+		hwc->last_period = period;
+		overflow = 1;
+	}
+
+	if (unlikely(left <= 0)) {
+		left += period;
+		local64_set(&hwc->period_left, left);
+		hwc->last_period = period;
+		overflow = 1;
+	}
+
+	/*
+	 * Limit the maximum period to prevent the counter value
+	 * from overtaking the one we are about to program. In
+	 * effect we are reducing max_period to account for
+	 * interrupt latency (and we are being very conservative).
+	 */
+	if (left > (max_period >> 1))
+		left = (max_period >> 1);
+
+	local64_set(&hwc->prev_count, (u64)-left);
+
+	return overflow;
+}
+
+void riscv_pmu_start(struct perf_event *event, int flags)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
+	uint64_t max_period = riscv_pmu_ctr_get_width_mask(event);
+	u64 init_val;
+
+	if (flags & PERF_EF_RELOAD)
+		WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
+
+	hwc->state = 0;
+	riscv_pmu_event_set_period(event);
+	init_val = local64_read(&hwc->prev_count) & max_period;
+	rvpmu->ctr_start(event, init_val);
+	perf_event_update_userpage(event);
+}
+
+static int riscv_pmu_add(struct perf_event *event, int flags)
+{
+	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
+	struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
+	struct hw_perf_event *hwc = &event->hw;
+	int idx;
+
+	idx = rvpmu->ctr_get_idx(event);
+	if (idx < 0)
+		return idx;
+
+	hwc->idx = idx;
+	cpuc->events[idx] = event;
+	cpuc->n_events++;
+	hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
+	if (flags & PERF_EF_START)
+		riscv_pmu_start(event, PERF_EF_RELOAD);
+
+	/* Propagate our changes to the userspace mapping. */
+	perf_event_update_userpage(event);
+
+	return 0;
+}
+
+static void riscv_pmu_del(struct perf_event *event, int flags)
+{
+	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
+	struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
+	struct hw_perf_event *hwc = &event->hw;
+
+	riscv_pmu_stop(event, PERF_EF_UPDATE);
+	cpuc->events[hwc->idx] = NULL;
+	/* The firmware need to reset the counter mapping */
+	if (rvpmu->ctr_stop)
+		rvpmu->ctr_stop(event, RISCV_PMU_STOP_FLAG_RESET);
+	cpuc->n_events--;
+	if (rvpmu->ctr_clear_idx)
+		rvpmu->ctr_clear_idx(event);
+	perf_event_update_userpage(event);
+	hwc->idx = -1;
+}
+
+static void riscv_pmu_read(struct perf_event *event)
+{
+	riscv_pmu_event_update(event);
+}
+
+static int riscv_pmu_event_init(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
+	int mapped_event;
+	u64 event_config = 0;
+	uint64_t cmask;
+
+	hwc->flags = 0;
+	mapped_event = rvpmu->event_map(event, &event_config);
+	if (mapped_event < 0) {
+		pr_debug("event %x:%llx not supported\n", event->attr.type,
+			 event->attr.config);
+		return mapped_event;
+	}
+
+	/*
+	 * idx is set to -1 because the index of a general event should not be
+	 * decided until binding to some counter in pmu->add().
+	 * config will contain the information about counter CSR
+	 * the idx will contain the counter index
+	 */
+	hwc->config = event_config;
+	hwc->idx = -1;
+	hwc->event_base = mapped_event;
+
+	if (!is_sampling_event(event)) {
+		/*
+		 * For non-sampling runs, limit the sample_period to half
+		 * of the counter width. That way, the new counter value
+		 * is far less likely to overtake the previous one unless
+		 * you have some serious IRQ latency issues.
+		 */
+		cmask = riscv_pmu_ctr_get_width_mask(event);
+		hwc->sample_period  =  cmask >> 1;
+		hwc->last_period    = hwc->sample_period;
+		local64_set(&hwc->period_left, hwc->sample_period);
+	}
+
+	return 0;
+}
+
+struct riscv_pmu *riscv_pmu_alloc(void)
+{
+	struct riscv_pmu *pmu;
+	int cpuid, i;
+	struct cpu_hw_events *cpuc;
+
+	pmu = kzalloc(sizeof(*pmu), GFP_KERNEL);
+	if (!pmu)
+		goto out;
+
+	pmu->hw_events = alloc_percpu_gfp(struct cpu_hw_events, GFP_KERNEL);
+	if (!pmu->hw_events) {
+		pr_info("failed to allocate per-cpu PMU data.\n");
+		goto out_free_pmu;
+	}
+
+	for_each_possible_cpu(cpuid) {
+		cpuc = per_cpu_ptr(pmu->hw_events, cpuid);
+		cpuc->n_events = 0;
+		for (i = 0; i < RISCV_MAX_COUNTERS; i++)
+			cpuc->events[i] = NULL;
+	}
+	pmu->pmu = (struct pmu) {
+		.event_init	= riscv_pmu_event_init,
+		.add		= riscv_pmu_add,
+		.del		= riscv_pmu_del,
+		.start		= riscv_pmu_start,
+		.stop		= riscv_pmu_stop,
+		.read		= riscv_pmu_read,
+	};
+
+	return pmu;
+
+out_free_pmu:
+	kfree(pmu);
+out:
+	return NULL;
+}