X-Git-Url: http://review.tizen.org/git/?a=blobdiff_plain;f=arch%2Fx86%2Fkernel%2Freboot.c;h=c752cb43e52f192f431a5f2ab91b9366e42ef5b0;hb=2885432aaf15c1b7e65c787bfe7c5fec428296f0;hp=da3c599584a3307f024c76f80c94e721016765e3;hpb=d72681d7c61f32a89147b8867cfb80e4ea119972;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index da3c599..c752cb4 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -558,6 +558,17 @@ void native_machine_shutdown(void)
 {
 	/* Stop the cpus and apics */
 #ifdef CONFIG_X86_IO_APIC
+	/*
+	 * Disabling IO APIC before local APIC is a workaround for
+	 * erratum AVR31 in "Intel Atom Processor C2000 Product Family
+	 * Specification Update". In this situation, interrupts that target
+	 * a Logical Processor whose Local APIC is either in the process of
+	 * being hardware disabled or software disabled are neither delivered
+	 * nor discarded. When this erratum occurs, the processor may hang.
+	 *
+	 * Even without the erratum, it still makes sense to quiet IO APIC
+	 * before disabling Local APIC.
+	 */
 	disable_IO_APIC();
 #endif