genirq/timings: Add selftest for circular array

Due to the complexity of the code and the difficulty to debug it, add some
selftests to the framework in order to spot issues or regression at boot
time when the runtime testing is enabled for this subsystem.

This tests the circular buffer at the limits and validates:
 - the encoding / decoding of the values
 - the macro to browse the irq timings circular buffer
 - the function to push data in the circular buffer

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20190527205521.12091-7-daniel.lezcano@linaro.org

diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile
index ff6e352e3a6cbc7409f6170e1b0c8a66cefb3e61..b4f53717d1434fd3296e72707513a1de7d30897b 100644 (file)
--- a/kernel/irq/Makefile
+++ b/kernel/irq/Makefile
@@ -2,6 +2,9 @@
 
 obj-y := irqdesc.o handle.o manage.o spurious.o resend.o chip.o dummychip.o devres.o
 obj-$(CONFIG_IRQ_TIMINGS) += timings.o
+ifeq ($(CONFIG_TEST_IRQ_TIMINGS),y)
+       CFLAGS_timings.o += -DDEBUG
+endif
 obj-$(CONFIG_GENERIC_IRQ_CHIP) += generic-chip.o
 obj-$(CONFIG_GENERIC_IRQ_PROBE) += autoprobe.o
 obj-$(CONFIG_IRQ_DOMAIN) += irqdomain.o

diff --git a/kernel/irq/timings.c b/kernel/irq/timings.c
index bc04eca6ef84727bfb429537c15c5b3486494cf3..95b63bdea156f95c41bafffb7a02146bc0c2d60e 100644 (file)
--- a/kernel/irq/timings.c
+++ b/kernel/irq/timings.c
@@ -1,10 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (C) 2016, Linaro Ltd - Daniel Lezcano <daniel.lezcano@linaro.org>
+#define pr_fmt(fmt) "irq_timings: " fmt
 
 #include <linux/kernel.h>
 #include <linux/percpu.h>
 #include <linux/slab.h>
 #include <linux/static_key.h>
+#include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/idr.h>
 #include <linux/irq.h>
@@ -625,3 +627,120 @@ int irq_timings_alloc(int irq)
 
        return 0;
 }
+
+#ifdef CONFIG_TEST_IRQ_TIMINGS
+static int __init irq_timings_test_irqts(struct irq_timings *irqts,
+                                        unsigned count)
+{
+       int start = count >= IRQ_TIMINGS_SIZE ? count - IRQ_TIMINGS_SIZE : 0;
+       int i, irq, oirq = 0xBEEF;
+       u64 ots = 0xDEAD, ts;
+
+       /*
+        * Fill the circular buffer by using the dedicated function.
+        */
+       for (i = 0; i < count; i++) {
+               pr_debug("%d: index=%d, ts=%llX irq=%X\n",
+                        i, i & IRQ_TIMINGS_MASK, ots + i, oirq + i);
+
+               irq_timings_push(ots + i, oirq + i);
+       }
+
+       /*
+        * Compute the first elements values after the index wrapped
+        * up or not.
+        */
+       ots += start;
+       oirq += start;
+
+       /*
+        * Test the circular buffer count is correct.
+        */
+       pr_debug("---> Checking timings array count (%d) is right\n", count);
+       if (WARN_ON(irqts->count != count))
+               return -EINVAL;
+
+       /*
+        * Test the macro allowing to browse all the irqts.
+        */
+       pr_debug("---> Checking the for_each_irqts() macro\n");
+       for_each_irqts(i, irqts) {
+
+               irq = irq_timing_decode(irqts->values[i], &ts);
+
+               pr_debug("index=%d, ts=%llX / %llX, irq=%X / %X\n",
+                        i, ts, ots, irq, oirq);
+
+               if (WARN_ON(ts != ots || irq != oirq))
+                       return -EINVAL;
+
+               ots++; oirq++;
+       }
+
+       /*
+        * The circular buffer should have be flushed when browsed
+        * with for_each_irqts
+        */
+       pr_debug("---> Checking timings array is empty after browsing it\n");
+       if (WARN_ON(irqts->count))
+               return -EINVAL;
+
+       return 0;
+}
+
+static int __init irq_timings_irqts_selftest(void)
+{
+       struct irq_timings *irqts = this_cpu_ptr(&irq_timings);
+       int i, ret;
+
+       /*
+        * Test the circular buffer with different number of
+        * elements. The purpose is to test at the limits (empty, half
+        * full, full, wrapped with the cursor at the boundaries,
+        * wrapped several times, etc ...
+        */
+       int count[] = { 0,
+                       IRQ_TIMINGS_SIZE >> 1,
+                       IRQ_TIMINGS_SIZE,
+                       IRQ_TIMINGS_SIZE + (IRQ_TIMINGS_SIZE >> 1),
+                       2 * IRQ_TIMINGS_SIZE,
+                       (2 * IRQ_TIMINGS_SIZE) + 3,
+       };
+
+       for (i = 0; i < ARRAY_SIZE(count); i++) {
+
+               pr_info("---> Checking the timings with %d/%d values\n",
+                       count[i], IRQ_TIMINGS_SIZE);
+
+               ret = irq_timings_test_irqts(irqts, count[i]);
+               if (ret)
+                       break;
+       }
+
+       return ret;
+}
+
+static int __init irq_timings_selftest(void)
+{
+       int ret;
+
+       pr_info("------------------- selftest start -----------------\n");
+
+       /*
+        * At this point, we don't except any subsystem to use the irq
+        * timings but us, so it should not be enabled.
+        */
+       if (static_branch_unlikely(&irq_timing_enabled)) {
+               pr_warn("irq timings already initialized, skipping selftest\n");
+               return 0;
+       }
+
+       ret = irq_timings_irqts_selftest();
+
+       pr_info("---------- selftest end with %s -----------\n",
+               ret ? "failure" : "success");
+
+       return ret;
+}
+early_initcall(irq_timings_selftest);
+#endif

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cbdfae37989653410332bc9acd9dd1237ace1712..f0788eea64bd6c6a31fbcab976a56ffed7e81177 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1858,6 +1858,14 @@ config TEST_PARMAN
 
          If unsure, say N.
 
+config TEST_IRQ_TIMINGS
+       bool "IRQ timings selftest"
+       depends on IRQ_TIMINGS
+       help
+         Enable this option to test the irq timings code on boot.
+
+         If unsure, say N.
+
 config TEST_LKM
        tristate "Test module loading with 'hello world' module"
        depends on m