xref: /openbmc/u-boot/arch/arm/lib/cmd_boot.c (revision 274bced8)
1 /*
2  * (C) Copyright 2008-2011
3  * Graeme Russ, <graeme.russ@gmail.com>
4  *
5  * (C) Copyright 2002
6  * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
7  *
8  * (C) Copyright 2002
9  * Wolfgang Denk, DENX Software Engineering, <wd@denx.de>
10  *
11  * (C) Copyright 2002
12  * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
13  * Marius Groeger <mgroeger@sysgo.de>
14  *
15  * Copyright 2015 ATS Advanced Telematics Systems GmbH
16  * Copyright 2015 Konsulko Group, Matt Porter <mporter@konsulko.com>
17  *
18  * SPDX-License-Identifier:	GPL-2.0+
19  */
20 
21 #include <common.h>
22 #include <command.h>
23 
24 DECLARE_GLOBAL_DATA_PTR;
25 
26 /*
27  * ARMv7M does not support ARM instruction mode. However, the
28  * interworking BLX and BX instructions do encode the ARM/Thumb
29  * field in bit 0. This means that when executing any Branch
30  * and eXchange instruction we must set bit 0 to one to guarantee
31  * that we keep the processor in Thumb instruction mode. From The
32  * ARMv7-M Instruction Set A4.1.1:
33  *   "ARMv7-M only supports the Thumb instruction execution state,
34  *    therefore the value of address bit [0] must be 1 in interworking
35  *    instructions, otherwise a fault occurs."
36  */
37 unsigned long do_go_exec(ulong (*entry)(int, char * const []),
38 			 int argc, char * const argv[])
39 {
40 	ulong addr = (ulong)entry | 1;
41 	entry = (void *)addr;
42 
43 	return entry(argc, argv);
44 }
45