sh: perf events: Add preliminary support for SH-4A counters.

This adds in preliminary support for the SH-4A performance counters.
Presently only the first 2 counters are supported, as these are the ones
of the most interest to the perf tool and end users. Counter chaining is
not presently handled, so these are simply implemented as 32-bit
counters.

This also establishes a perf event support framework for other hardware
counters, which the existing SH-4 oprofile code will migrate over to as
the SH-4A support evolves.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 314 insertions, 0 deletions

diff --git a/arch/sh/kernel/perf_event.c b/arch/sh/kernel/perf_event.c
new file mode 100644
index 0000000..d151070
--- /dev/null
+++ b/arch/sh/kernel/perf_event.c
@@ -0,0 +1,314 @@
+/*
+ * Performance event support framework for SuperH hardware counters.
+ *
+ *  Copyright (C) 2009  Paul Mundt
+ *
+ * Heavily based on the x86 and PowerPC implementations.
+ *
+ * x86:
+ *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
+ *  Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
+ *  Copyright (C) 2009 Jaswinder Singh Rajput
+ *  Copyright (C) 2009 Advanced Micro Devices, Inc., Robert Richter
+ *  Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
+ *  Copyright (C) 2009 Intel Corporation, <markus.t.metzger@intel.com>
+ *
+ * ppc:
+ *  Copyright 2008-2009 Paul Mackerras, IBM Corporation.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/perf_event.h>
+#include <asm/processor.h>
+
+struct cpu_hw_events {
+	struct perf_event	*events[MAX_HWEVENTS];
+	unsigned long		used_mask[BITS_TO_LONGS(MAX_HWEVENTS)];
+	unsigned long		active_mask[BITS_TO_LONGS(MAX_HWEVENTS)];
+};
+
+DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);
+
+static struct sh_pmu *sh_pmu __read_mostly;
+
+/* Number of perf_events counting hardware events */
+static atomic_t num_events;
+/* Used to avoid races in calling reserve/release_pmc_hardware */
+static DEFINE_MUTEX(pmc_reserve_mutex);
+
+/*
+ * Stub these out for now, do something more profound later.
+ */
+int reserve_pmc_hardware(void)
+{
+	return 0;
+}
+
+void release_pmc_hardware(void)
+{
+}
+
+static inline int sh_pmu_initialized(void)
+{
+	return !!sh_pmu;
+}
+
+/*
+ * Release the PMU if this is the last perf_event.
+ */
+static void hw_perf_event_destroy(struct perf_event *event)
+{
+	if (!atomic_add_unless(&num_events, -1, 1)) {
+		mutex_lock(&pmc_reserve_mutex);
+		if (atomic_dec_return(&num_events) == 0)
+			release_pmc_hardware();
+		mutex_unlock(&pmc_reserve_mutex);
+	}
+}
+
+static int hw_perf_cache_event(int config, int *evp)
+{
+	unsigned long type, op, result;
+	int ev;
+
+	if (!sh_pmu->cache_events)
+		return -EINVAL;
+
+	/* unpack config */
+	type = config & 0xff;
+	op = (config >> 8) & 0xff;
+	result = (config >> 16) & 0xff;
+
+	if (type >= PERF_COUNT_HW_CACHE_MAX ||
+	    op >= PERF_COUNT_HW_CACHE_OP_MAX ||
+	    result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
+		return -EINVAL;
+
+	ev = (*sh_pmu->cache_events)[type][op][result];
+	if (ev == 0)
+		return -EOPNOTSUPP;
+	if (ev == -1)
+		return -EINVAL;
+	*evp = ev;
+	return 0;
+}
+
+static int __hw_perf_event_init(struct perf_event *event)
+{
+	struct perf_event_attr *attr = &event->attr;
+	struct hw_perf_event *hwc = &event->hw;
+	int config;
+	int err;
+
+	if (!sh_pmu_initialized())
+		return -ENODEV;
+
+	/*
+	 * All of the on-chip counters are "limited", in that they have
+	 * no interrupts, and are therefore unable to do sampling without
+	 * further work and timer assistance.
+	 */
+	if (hwc->sample_period)
+		return -EINVAL;
+
+	/*
+	 * See if we need to reserve the counter.
+	 *
+	 * If no events are currently in use, then we have to take a
+	 * mutex to ensure that we don't race with another task doing
+	 * reserve_pmc_hardware or release_pmc_hardware.
+	 */
+	err = 0;
+	if (!atomic_inc_not_zero(&num_events)) {
+		mutex_lock(&pmc_reserve_mutex);
+		if (atomic_read(&num_events) == 0 &&
+		    reserve_pmc_hardware())
+			err = -EBUSY;
+		else
+			atomic_inc(&num_events);
+		mutex_unlock(&pmc_reserve_mutex);
+	}
+
+	if (err)
+		return err;
+
+	event->destroy = hw_perf_event_destroy;
+
+	switch (attr->type) {
+	case PERF_TYPE_RAW:
+		config = attr->config & sh_pmu->raw_event_mask;
+		break;
+	case PERF_TYPE_HW_CACHE:
+		err = hw_perf_cache_event(attr->config, &config);
+		if (err)
+			return err;
+		break;
+	case PERF_TYPE_HARDWARE:
+		if (attr->config >= sh_pmu->max_events)
+			return -EINVAL;
+
+		config = sh_pmu->event_map(attr->config);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (config == -1)
+		return -EINVAL;
+
+	hwc->config |= config;
+
+	return 0;
+}
+
+static void sh_perf_event_update(struct perf_event *event,
+				   struct hw_perf_event *hwc, int idx)
+{
+	u64 prev_raw_count, new_raw_count;
+	s64 delta;
+	int shift = 0;
+
+	/*
+	 * Depending on the counter configuration, they may or may not
+	 * be chained, in which case the previous counter value can be
+	 * updated underneath us if the lower-half overflows.
+	 *
+	 * Our tactic to handle this is to first atomically read and
+	 * exchange a new raw count - then add that new-prev delta
+	 * count to the generic counter atomically.
+	 *
+	 * As there is no interrupt associated with the overflow events,
+	 * this is the simplest approach for maintaining consistency.
+	 */
+again:
+	prev_raw_count = atomic64_read(&hwc->prev_count);
+	new_raw_count = sh_pmu->read(idx);
+
+	if (atomic64_cmpxchg(&hwc->prev_count, prev_raw_count,
+			     new_raw_count) != prev_raw_count)
+		goto again;
+
+	/*
+	 * Now we have the new raw value and have updated the prev
+	 * timestamp already. We can now calculate the elapsed delta
+	 * (counter-)time and add that to the generic counter.
+	 *
+	 * Careful, not all hw sign-extends above the physical width
+	 * of the count.
+	 */
+	delta = (new_raw_count << shift) - (prev_raw_count << shift);
+	delta >>= shift;
+
+	atomic64_add(delta, &event->count);
+}
+
+static void sh_pmu_disable(struct perf_event *event)
+{
+	struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+
+	clear_bit(idx, cpuc->active_mask);
+	sh_pmu->disable(hwc, idx);
+
+	barrier();
+
+	sh_perf_event_update(event, &event->hw, idx);
+
+	cpuc->events[idx] = NULL;
+	clear_bit(idx, cpuc->used_mask);
+
+	perf_event_update_userpage(event);
+}
+
+static int sh_pmu_enable(struct perf_event *event)
+{
+	struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+	struct hw_perf_event *hwc = &event->hw;
+	int idx = hwc->idx;
+
+	if (test_and_set_bit(idx, cpuc->used_mask)) {
+		idx = find_first_zero_bit(cpuc->used_mask, sh_pmu->num_events);
+		if (idx == sh_pmu->num_events)
+			return -EAGAIN;
+
+		set_bit(idx, cpuc->used_mask);
+		hwc->idx = idx;
+	}
+
+	sh_pmu->disable(hwc, idx);
+
+	cpuc->events[idx] = event;
+	set_bit(idx, cpuc->active_mask);
+
+	sh_pmu->enable(hwc, idx);
+
+	perf_event_update_userpage(event);
+
+	return 0;
+}
+
+static void sh_pmu_read(struct perf_event *event)
+{
+	sh_perf_event_update(event, &event->hw, event->hw.idx);
+}
+
+static const struct pmu pmu = {
+	.enable		= sh_pmu_enable,
+	.disable	= sh_pmu_disable,
+	.read		= sh_pmu_read,
+};
+
+const struct pmu *hw_perf_event_init(struct perf_event *event)
+{
+	int err = __hw_perf_event_init(event);
+	if (unlikely(err)) {
+		if (event->destroy)
+			event->destroy(event);
+		return ERR_PTR(err);
+	}
+
+	return &pmu;
+}
+
+void hw_perf_event_setup(int cpu)
+{
+	struct cpu_hw_events *cpuhw = &per_cpu(cpu_hw_events, cpu);
+
+	memset(cpuhw, 0, sizeof(struct cpu_hw_events));
+}
+
+void hw_perf_enable(void)
+{
+	if (!sh_pmu_initialized())
+		return;
+
+	sh_pmu->enable_all();
+}
+
+void hw_perf_disable(void)
+{
+	if (!sh_pmu_initialized())
+		return;
+
+	sh_pmu->disable_all();
+}
+
+int register_sh_pmu(struct sh_pmu *pmu)
+{
+	if (sh_pmu)
+		return -EBUSY;
+	sh_pmu = pmu;
+
+	pr_info("Performance Events: %s support registered\n", pmu->name);
+
+	WARN_ON(pmu->num_events >= MAX_HWEVENTS);
+
+	return 0;
+}