From d38ff30d88adbe51d50e0f4e66a819b31bd3b234 Mon Sep 17 00:00:00 2001
From: Werner Almesberger <werner@openmoko.org>
Date: Thu, 29 Jan 2009 14:27:33 +0000
Subject: Quick and dirty interrupt blocking time detector.

---
 arch/arm/kernel/Makefile |   1 +
 arch/arm/kernel/iblock.c | 158 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 159 insertions(+)
 create mode 100644 arch/arm/kernel/iblock.c

(limited to 'arch/arm/kernel')

diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 4305345987d..29d70d2ac86 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -44,5 +44,6 @@ endif
 
 head-y			:= head$(MMUEXT).o
 obj-$(CONFIG_DEBUG_LL)	+= debug.o
+obj-y			+= iblock.o
 
 extra-y := $(head-y) init_task.o vmlinux.lds
diff --git a/arch/arm/kernel/iblock.c b/arch/arm/kernel/iblock.c
new file mode 100644
index 00000000000..d869e790ec2
--- /dev/null
+++ b/arch/arm/kernel/iblock.c
@@ -0,0 +1,158 @@
+/*
+ *
+ * /sys/kernel/iblock/
+ * All times are in microseconds (us).
+ *
+ * - limit
+ *   Interrupt blocking time reporting limit, in microseconds.
+ *   0 disables reporting. Auto-resets to zero after reporting.
+ *
+ * - max
+ *   Maximum blocking time recorded. Reset to zero by writing anything.
+ *
+ * - test
+ *   Force a delay with interrupts disabled.
+ *
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/sysfs.h>
+#include <linux/kobject.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <asm/irqflags.h>
+
+
+unsigned long s3c2410_gettimeoffset(void);
+
+
+static unsigned long iblock_t0;
+static int iblock_limit;
+static int iblock_max;
+
+
+void iblock_start(void)
+{
+	unsigned long flags;
+
+	raw_local_save_flags(flags);
+	if (raw_irqs_disabled_flags(flags))
+		return;
+	iblock_t0 = s3c2410_gettimeoffset();
+}
+
+
+void iblock_end(void)
+{
+	unsigned long flags;
+	unsigned long t, us;
+
+	raw_local_save_flags(flags);
+	if (!raw_irqs_disabled_flags(flags))
+		return;
+	if (!iblock_t0)
+		return;
+	t = s3c2410_gettimeoffset();
+	us = t-iblock_t0;
+	if (us > 40000000)
+		return;
+	if (us > iblock_max)
+		iblock_max = us;
+	if (!iblock_limit)
+		return;
+	if (us < iblock_limit)
+		return;
+	iblock_limit = 0;
+	printk(KERN_ERR "interrupts were disabled for %lu us !\n", us);
+	WARN_ON(1);
+}
+
+
+void iblock_end_maybe(unsigned long flags)
+{
+	if (raw_irqs_disabled_flags(flags))
+		return;
+	iblock_end();
+}
+
+
+static ssize_t limit_read(struct device *dev, struct device_attribute *attr,
+    char *buf)
+{
+	return sprintf(buf, "%u us\n", iblock_limit);
+}
+
+
+static ssize_t limit_write(struct device *dev, struct device_attribute *attr,
+    const char *buf, size_t count)
+{
+	unsigned long tmp;
+	char *end;
+
+	tmp = simple_strtoul(buf, &end, 0);
+	if (end == buf)
+		return -EINVAL;
+	iblock_limit = tmp;
+	return count;
+}
+
+
+static ssize_t max_read(struct device *dev, struct device_attribute *attr,
+    char *buf)
+{
+	return sprintf(buf, "%u us\n", iblock_max);
+}
+
+
+static ssize_t max_write(struct device *dev, struct device_attribute *attr,
+    const char *buf, size_t count)
+{
+	iblock_max = 0;
+	return count;
+}
+
+
+static ssize_t test_write(struct device *dev,
+    struct device_attribute *attr, const char *buf, size_t count)
+{
+	unsigned long tmp, flags;
+	char *end;
+
+	tmp = simple_strtoul(buf, &end, 0);
+	if (end == buf)
+		return -EINVAL;
+	local_irq_save(flags);
+	udelay(tmp);
+	local_irq_restore(flags);
+	return count;
+}
+
+
+static DEVICE_ATTR(limit, 0644, limit_read, limit_write);
+static DEVICE_ATTR(max, 0644, max_read, max_write);
+static DEVICE_ATTR(test, 0200, NULL, test_write);
+
+
+static struct attribute *sysfs_entries[] = {
+	&dev_attr_limit.attr,
+	&dev_attr_max.attr,
+	&dev_attr_test.attr,
+	NULL
+};
+
+
+static struct attribute_group attr_group = {
+	.name	= "iblock",
+	.attrs	= sysfs_entries,
+};
+
+
+static int __devinit iblock_init(void)
+{
+	return sysfs_create_group(kernel_kobj, &attr_group);
+}
+
+
+module_init(iblock_init);
-- 
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