[PATCH V3 8/8] genirq/timings: Add selftest for next event computation

[Daniel Lezcano]

The circular buffers are now validated at this point with the two
previous patches. The next interrupt index algorithm which is the
hardest part to validate can be validated with the tests provided with
this patch.

It uses the intervals stored in the arrays and insert all the values
except the last one. The next event computation must return the same
value as the last element we did not inserted.

Add tests for the next event index computation.

Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
---
 kernel/irq/timings.c | 66 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/kernel/irq/timings.c b/kernel/irq/timings.c
index 5b13c2231d4f..e960d7ce7bcc 100644
--- a/kernel/irq/timings.c
+++ b/kernel/irq/timings.c
@@ -704,6 +704,68 @@ static struct timings_intervals tis[] __initdata = {
 	{ intervals4, ARRAY_SIZE(intervals4) },
 };
 
+static int __init irq_timings_test_next_index(struct timings_intervals *ti)
+{
+	int _buffer[IRQ_TIMINGS_SIZE];
+	int buffer[IRQ_TIMINGS_SIZE];
+	int index, start, i, count, period_max;
+
+	count = ti->count - 1;
+
+	period_max = count > (3 * PREDICTION_PERIOD_MAX) ?
+		PREDICTION_PERIOD_MAX : count / 3;
+
+	/*
+	 * Inject all values except the last one which will be used
+	 * to compare with the next index result.
+	 */
+	pr_debug("index suite: ");
+
+	for (i = 0; i < count; i++) {
+		index = irq_timings_interval_index(ti->intervals[i]);
+		_buffer[i & IRQ_TIMINGS_MASK] = index;
+		pr_cont("%d ", index);
+	}
+
+	start = count < IRQ_TIMINGS_SIZE ? 0 :
+		count & IRQ_TIMINGS_MASK;
+
+	count = min_t(int, count, IRQ_TIMINGS_SIZE);
+
+	for (i = 0; i < count; i++) {
+		int index = (start + i) & IRQ_TIMINGS_MASK;
+		buffer[i] = _buffer[index];
+	}
+
+	index = irq_timings_next_event_index(buffer, count, period_max);
+	i = irq_timings_interval_index(ti->intervals[ti->count - 1]);
+
+	if (index != i) {
+		pr_err("Expected (%d) and computed (%d) next indexes differ\n",
+		       i, index);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int __init irq_timings_next_index_selftest(void)
+{
+	int i, ret;
+
+	for (i = 0; i < ARRAY_SIZE(tis); i++) {
+
+		pr_info("---> Injecting intervals number #%d (count=%zd)\n",
+			i, tis[i].count);
+
+		ret = irq_timings_test_next_index(&tis[i]);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
 static int __init irq_timings_test_irqs(struct timings_intervals *ti)
 {
 	struct irqt_stat __percpu *s;
@@ -875,6 +937,10 @@ static int __init irq_timings_selftest(void)
 		goto out;
 
 	ret = irq_timings_irqs_selftest();
+	if (ret)
+		goto out;
+
+	ret = irq_timings_next_index_selftest();
 out:
 	pr_info("---------- selftest end with %s -----------\n",
 		ret ? "failure" : "success");
-- 
2.17.1