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/*
* Copyright (C) 2016 Bernhard Nortmann <bernhard.nortmann@web.de>
*
* Based on previous works
* Copyright (C) 2016 Siarhei Siamashka <siarhei.siamashka@gmail.com>
* Copyright (C) 2012 Henrik Nordstrom <henrik@henriknordstrom.net>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*
*/
/*
* This file is a utility stub (bootloader code) to force the device into
* FEL mode, by jumping directly to the corresponding (N-)BROM entry point.
*
* Build instructions:
* make fel-sdboot.sunxi
*
* If needed, adjust CROSS_COMPILE and MKSUNXIBOOT according to your
* toolchain, e.g.
* make fel-sdboot.sunxi CROSS_COMPILE=armv7a-hardfloat-linux-gnueabi- \
* MKSUNXIBOOT=/usr/local/bin/mksunxiboot
*
*
* Install instructions:
* dd if=fel-sdboot.sunxi of=/dev/sdX bs=1024 seek=8
*/
SCTRL .req r0
.equ V_BIT, (1 << 13)
.equ BROM_ENTRY_LOW, 0x00000020
.equ BROM_ENTRY_HIGH, 0xFFFF0020
/*
* In cases where insufficient padding is added by an old mksunxiboot,
* _start may be 0x20, which means that the instruction at 0x28 could get
* corrupted by the BROM - see https://patchwork.ozlabs.org/patch/622173/
*
* Apply a workaround to avoid (= skip over) that memory location.
* _main would be at 0x30 in that particular case. With newer (properly
* fixed) versions of mksunxiboot, this code ends up at higher addresses
* and will be moot, but harmless.
*/
_start:
b _main
nop
nop
nop
_main:
mrc p15, 0, SCTRL, c1, c0, 0
tst SCTRL, #V_BIT @ test SCTRL.V
moveq lr, #BROM_ENTRY_LOW
ldrne lr, =BROM_ENTRY_HIGH
bx lr
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