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>

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 @@ void cpu_init_f(ulong bootflag, ulong loaded_from_ldr)
 		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);

lib_blackfin/boot.c

@@ -31,6 +31,8 @@ static char *make_command_line(void)
 	return dest;
 }
 
+extern ulong bfin_poweron_retx;
+
 int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
 {
 	int	(*appl) (char *cmdline);
@@ -49,7 +51,12 @@ int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
 	cmdline = make_command_line();
 	icache_disable();
 	dcache_disable();
-	(*appl) (cmdline);
+	asm __volatile__(
+		"RETX = %[retx];"
+		"CALL (%0);"
+		:
+		: "p"(appl), "q0"(cmdline), [retx] "d"(bfin_poweron_retx)
+	);
 	/* does not return */
 
 	return 1;