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Diffstat (limited to 'system/arm/simple_bootloader/simple.S')
| -rw-r--r-- | system/arm/simple_bootloader/simple.S | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/system/arm/simple_bootloader/simple.S b/system/arm/simple_bootloader/simple.S new file mode 100644 index 000000000..d8f2905e9 --- /dev/null +++ b/system/arm/simple_bootloader/simple.S @@ -0,0 +1,71 @@ +/* + * Copyright (c) 2010 ARM Limited + * All rights reserved + * + * The license below extends only to copyright in the software and shall + * not be construed as granting a license to any other intellectual + * property including but not limited to intellectual property relating + * to a hardware implementation of the functionality of the software + * licensed hereunder. You may use the software subject to the license + * terms below provided that you ensure that this notice is replicated + * unmodified and in its entirety in all distributions of the software, + * modified or unmodified, in source code or in binary form. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer; + * redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution; + * neither the name of the copyright holders nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * Authors: Ali Saidi + */ + +/************************************************************************* + * Super simple bootloader + * Preserve loaded values that we need to pass to the kernel (r0, r1, r2) + * Additionally M5 puts the kernel start address in r3 + * + * Upon executing this code: + * r0 = 0, r1 = machine number, r2 = atags ptr + * r3 = kernel start address + * + * CPU 0 should branch to the kernel start address and it's done with + * the boot loader. Other CPUs need to start in a wfi loop. When CPU0 sends + * an IPI the slave CPUs reads a register which CPU0 has programmed with the + * boot address for the secondary cpu + **************************************************************************/ +.text +.globl _start +.extern main +_start: +_entry: + mrc p15, 0, r4, c0, c0, 5 // get the MPIDR register + uxtb r4, r4 // isolate the lower 8 bits (affinity lvl 1) + adds r4, r4, #0 // set flags for branch + bxeq r3 // if it's 0 (CPU 0), branch to kernel +pen: + wfi // otherwise wait for an interrupt + mov r4, #0x30 // Build address of the system controller + movt r4, #0x1000 // flag register r4 = 0x10000030 + ldr r5, [r4] // load the value + movs r5, r5 // set the flags on this value + beq pen // if it's zero try again + bx r5 // Jump to where we've been told + bkpt // We should never get here |