Blackfin: pass RETX to Linux

Make sure we save the value of RETX at power on and then pass it on to the
kernel so that it can nicely debug a "double-fault-caused-a-reset" crash.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/cpu/blackfin/cpu.c b/cpu/blackfin/cpu.c
index 9efd88e..30c214b 100644
--- a/cpu/blackfin/cpu.c
+++ b/cpu/blackfin/cpu.c
@@ -14,11 +14,14 @@
 #include <asm/blackfin.h>
 #include <asm/cplb.h>
 #include <asm/mach-common/bits/core.h>
+#include <asm/mach-common/bits/ebiu.h>
 #include <asm/mach-common/bits/trace.h>
 
 #include "cpu.h"
 #include "serial.h"
 
+ulong bfin_poweron_retx;
+
 __attribute__ ((__noreturn__))
 void cpu_init_f(ulong bootflag, ulong loaded_from_ldr)
 {
@@ -48,6 +51,9 @@
 		bfin_write_EBIU_AMGCTL(CONFIG_EBIU_AMGCTL_VAL);
 #endif
 
+	/* Save RETX so we can pass it while booting Linux */
+	bfin_poweron_retx = bootflag;
+
 #ifdef CONFIG_DEBUG_DUMP
 	/* Turn on hardware trace buffer */
 	bfin_write_TBUFCTL(TBUFPWR | TBUFEN);