[AVR32] NMI debugging

Change the NMI handler to use the die notifier chain to signal anyone
who cares. Add a simple "nmi debugger" which hooks into this chain and
that may dump registers, task state, etc. when it happens.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

Documentation/kernel-parameters.txt

@@ -34,6 +34,7 @@ parameter is applicable:
 	ALSA	ALSA sound support is enabled.
 	APIC	APIC support is enabled.
 	APM	Advanced Power Management support is enabled.
+	AVR32	AVR32 architecture is enabled.
 	AX25	Appropriate AX.25 support is enabled.
 	BLACKFIN Blackfin architecture is enabled.
 	DRM	Direct Rendering Management support is enabled.
@@ -1123,6 +1124,10 @@ and is between 256 and 4096 characters. It is defined in the file
 			of returning the full 64-bit number.
 			The default is to return 64-bit inode numbers.
 
+	nmi_debug=	[KNL,AVR32] Specify one or more actions to take
+			when a NMI is triggered.
+			Format: [state][,regs][,debounce][,die]
+
 	nmi_watchdog=	[KNL,BUGS=X86-32] Debugging features for SMP kernels
 
 	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths

arch/avr32/Kconfig

@@ -170,6 +170,16 @@ config OWNERSHIP_TRACE
 	  enabling Nexus-compliant debuggers to keep track of the PID of the
 	  currently executing task.
 
+config NMI_DEBUGGING
+	bool "NMI Debugging"
+	default n
+	help
+	  Say Y here and pass the nmi_debug command-line parameter to
+	  the kernel to turn on NMI debugging. Depending on the value
+	  of the nmi_debug option, various pieces of information will
+	  be dumped to the console when a Non-Maskable Interrupt
+	  happens.
+
 # FPU emulation goes here
 
 source "kernel/Kconfig.hz"

arch/avr32/kernel/Makefile

@@ -12,3 +12,4 @@ obj-y				+= init_task.o switch_to.o cpu.o
 obj-$(CONFIG_MODULES)		+= module.o avr32_ksyms.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
+obj-$(CONFIG_NMI_DEBUGGING)	+= nmi_debug.o

arch/avr32/kernel/irq.c

@@ -25,6 +25,17 @@ void ack_bad_irq(unsigned int irq)
 	printk("unexpected IRQ %u\n", irq);
 }
 
+/* May be overridden by platform code */
+int __weak nmi_enable(void)
+{
+	return -ENOSYS;
+}
+
+void __weak nmi_disable(void)
+{
+
+}
+
 #ifdef CONFIG_PROC_FS
 int show_interrupts(struct seq_file *p, void *v)
 {

arch/avr32/kernel/nmi_debug.c

+/*
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/delay.h>
+#include <linux/kdebug.h>
+#include <linux/notifier.h>
+#include <linux/sched.h>
+
+#include <asm/irq.h>
+
+enum nmi_action {
+	NMI_SHOW_STATE	= 1 << 0,
+	NMI_SHOW_REGS	= 1 << 1,
+	NMI_DIE		= 1 << 2,
+	NMI_DEBOUNCE	= 1 << 3,
+};
+
+static unsigned long nmi_actions;
+
+static int nmi_debug_notify(struct notifier_block *self,
+		unsigned long val, void *data)
+{
+	struct die_args *args = data;
+
+	if (likely(val != DIE_NMI))
+		return NOTIFY_DONE;
+
+	if (nmi_actions & NMI_SHOW_STATE)
+		show_state();
+	if (nmi_actions & NMI_SHOW_REGS)
+		show_regs(args->regs);
+	if (nmi_actions & NMI_DEBOUNCE)
+		mdelay(10);
+	if (nmi_actions & NMI_DIE)
+		return NOTIFY_BAD;
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block nmi_debug_nb = {
+	.notifier_call = nmi_debug_notify,
+};
+
+static int __init nmi_debug_setup(char *str)
+{
+	char *p, *sep;
+
+	register_die_notifier(&nmi_debug_nb);
+	if (nmi_enable()) {
+		printk(KERN_WARNING "Unable to enable NMI.\n");
+		return 0;
+	}
+
+	if (*str != '=')
+		return 0;
+
+	for (p = str + 1; *p; p = sep + 1) {
+		sep = strchr(p, ',');
+		if (sep)
+			*sep = 0;
+		if (strcmp(p, "state") == 0)
+			nmi_actions |= NMI_SHOW_STATE;
+		else if (strcmp(p, "regs") == 0)
+			nmi_actions |= NMI_SHOW_REGS;
+		else if (strcmp(p, "debounce") == 0)
+			nmi_actions |= NMI_DEBOUNCE;
+		else if (strcmp(p, "die") == 0)
+			nmi_actions |= NMI_DIE;
+		else
+			printk(KERN_WARNING "NMI: Unrecognized action `%s'\n",
+				p);
+		if (!sep)
+			break;
+	}
+
+	return 0;
+}
+__setup("nmi_debug", nmi_debug_setup);

arch/avr32/kernel/traps.c

@@ -9,6 +9,7 @@
 #include <linux/bug.h>
 #include <linux/init.h>
 #include <linux/kallsyms.h>
+#include <linux/kdebug.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
 #include <linux/sched.h>
@@ -107,9 +108,23 @@ void _exception(long signr, struct pt_regs *regs, int code,
 
 asmlinkage void do_nmi(unsigned long ecr, struct pt_regs *regs)
 {
-	printk(KERN_ALERT "Got Non-Maskable Interrupt, dumping regs\n");
-	show_regs_log_lvl(regs, KERN_ALERT);
-	show_stack_log_lvl(current, regs->sp, regs, KERN_ALERT);
+	int ret;
+
+	nmi_enter();
+
+	ret = notify_die(DIE_NMI, "NMI", regs, 0, ecr, SIGINT);
+	switch (ret) {
+	case NOTIFY_OK:
+	case NOTIFY_STOP:
+		return;
+	case NOTIFY_BAD:
+		die("Fatal Non-Maskable Interrupt", regs, SIGINT);
+	default:
+		break;
+	}
+
+	printk(KERN_ALERT "Got NMI, but nobody cared. Disabling...\n");
+	nmi_disable();
 }
 
 asmlinkage void do_critical_exception(unsigned long ecr, struct pt_regs *regs)

arch/avr32/mach-at32ap/at32ap700x.c

@@ -13,6 +13,7 @@
 #include <linux/spi/spi.h>
 
 #include <asm/io.h>
+#include <asm/irq.h>
 
 #include <asm/arch/at32ap700x.h>
 #include <asm/arch/board.h>

arch/avr32/mach-at32ap/extint.c

@@ -26,16 +26,10 @@
 #define EIC_MODE				0x0014
 #define EIC_EDGE				0x0018
 #define EIC_LEVEL				0x001c
-#define EIC_TEST				0x0020
 #define EIC_NMIC				0x0024
 
-/* Bitfields in TEST */
-#define EIC_TESTEN_OFFSET			31
-#define EIC_TESTEN_SIZE				1
-
 /* Bitfields in NMIC */
-#define EIC_EN_OFFSET				0
-#define EIC_EN_SIZE				1
+#define EIC_NMIC_ENABLE				(1 << 0)
 
 /* Bit manipulation macros */
 #define EIC_BIT(name)					\
@@ -63,6 +57,9 @@ struct eic {
 	unsigned int first_irq;
 };
 
+static struct eic *nmi_eic;
+static bool nmi_enabled;
+
 static void eic_ack_irq(unsigned int irq)
 {
 	struct eic *eic = get_irq_chip_data(irq);
@@ -174,6 +171,24 @@ static void demux_eic_irq(unsigned int irq, struct irq_desc *desc)
 	}
 }
 
+int nmi_enable(void)
+{
+	nmi_enabled = true;
+
+	if (nmi_eic)
+		eic_writel(nmi_eic, NMIC, EIC_NMIC_ENABLE);
+
+	return 0;
+}
+
+void nmi_disable(void)
+{
+	if (nmi_eic)
+		eic_writel(nmi_eic, NMIC, 0);
+
+	nmi_enabled = false;
+}
+
 static int __init eic_probe(struct platform_device *pdev)
 {
 	struct eic *eic;
@@ -230,6 +245,16 @@ static int __init eic_probe(struct platform_device *pdev)
 	set_irq_chained_handler(int_irq, demux_eic_irq);
 	set_irq_data(int_irq, eic);
 
+	if (pdev->id == 0) {
+		nmi_eic = eic;
+		if (nmi_enabled)
+			/*
+			 * Someone tried to enable NMI before we were
+			 * ready. Do it now.
+			 */
+			nmi_enable();
+	}
+
 	dev_info(&pdev->dev,
 		 "External Interrupt Controller at 0x%p, IRQ %u\n",
 		 eic->regs, int_irq);

include/asm-avr32/irq.h

@@ -11,4 +11,9 @@
 
 #define irq_canonicalize(i)	(i)
 
+#ifndef __ASSEMBLER__
+int nmi_enable(void);
+void nmi_disable(void);
+#endif
+
 #endif /* __ASM_AVR32_IOCTLS_H */

include/asm-avr32/kdebug.h

@@ -5,6 +5,7 @@
 enum die_val {
 	DIE_BREAKPOINT,
 	DIE_SSTEP,
+	DIE_NMI,
 };
 
 #endif /* __ASM_AVR32_KDEBUG_H */