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