MIPS: Add NMI notifier

Allow the board support code to register a raw notifier callback for
NMI, similar to what is done for CU2 exceptions.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2958/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 21 insertions, 0 deletions

diff --git a/arch/mips/include/asm/traps.h b/arch/mips/include/asm/traps.h
index 90ff2f497c50..4edab87eebd2 100644
--- a/arch/mips/include/asm/traps.h
+++ b/arch/mips/include/asm/traps.h
@@ -25,4 +25,16 @@ extern void (*board_nmi_handler_setup)(void);
 extern void (*board_ejtag_handler_setup)(void);
 extern void (*board_bind_eic_interrupt)(int irq, int regset);
 
+extern int register_nmi_notifier(struct notifier_block *nb);
+
+#define nmi_notifier(fn, pri)                                           \
+({                                                                      \
+        static struct notifier_block fn##_nb = {                        \
+                .notifier_call = fn,                                    \
+                .priority = pri                                         \
+        };                                                              \
+                                                                        \
+        register_nmi_notifier(&fn##_nb);                                \
+})
+
 #endif /* _ASM_TRAPS_H */
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 5c8a49d55054..33945aaa9b1b 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1339,9 +1339,18 @@ void ejtag_exception_handler(struct pt_regs *regs)
 
 /*
  * NMI exception handler.
+ * No lock; only written during early bootup by CPU 0.
  */
+static RAW_NOTIFIER_HEAD(nmi_chain);
+
+int register_nmi_notifier(struct notifier_block *nb)
+{
+        return raw_notifier_chain_register(&nmi_chain, nb);
+}
+
 NORET_TYPE void ATTRIB_NORET nmi_exception_handler(struct pt_regs *regs)
 {
+        raw_notifier_call_chain(&nmi_chain, 0, regs);
         bust_spinlocks(1);
         printk("NMI taken!!!!\n");
         die("NMI", regs);