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/*
* boot.S - simple register setup code for stand-alone Linux booting
*
* Copyright (C) 2012 ARM Limited. All rights reserved.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE.txt file.
*/
.text
.globl _start
_start:
/*
* EL3 initialisation
*/
mrs x0, CurrentEL
cmp x0, #0xc // EL3?
b.ne start_ns // skip EL3 initialisation
mov x0, #0x30 // RES1
orr x0, x0, #(1 << 0) // Non-secure EL1
orr x0, x0, #(1 << 8) // HVC enable
orr x0, x0, #(1 << 10) // 64-bit EL2
msr scr_el3, x0
msr cptr_el3, xzr // Disable copro. traps to EL3
ldr x0, =CNTFRQ
msr cntfrq_el0, x0
/*
* Check for the primary CPU to avoid a race on the distributor
* registers.
*/
mrs x0, mpidr_el1
tst x0, #15
b.ne 1f // secondary CPU
ldr x1, =GIC_DIST_BASE // GICD_CTLR
mov w0, #3 // EnableGrp0 | EnableGrp1
str w0, [x1]
1: ldr x1, =GIC_DIST_BASE + 0x80 // GICD_IGROUPR
mov w0, #~0 // Grp1 interrupts
str w0, [x1], #4
b.ne 2f // Only local interrupts for secondary CPUs
str w0, [x1], #4
str w0, [x1], #4
2: ldr x1, =GIC_CPU_BASE // GICC_CTLR
ldr w0, [x1]
mov w0, #3 // EnableGrp0 | EnableGrp1
str w0, [x1]
mov w0, #1 << 7 // allow NS access to GICC_PMR
str w0, [x1, #4] // GICC_PMR
msr sctlr_el2, xzr
/*
* Prepare the switch to the EL2_SP1 mode from EL3
*/
ldr x0, =start_ns // Return after mode switch
mov x1, #0x3c9 // EL2_SP1 | D | A | I | F
msr elr_el3, x0
msr spsr_el3, x1
eret
start_ns:
/*
* Kernel parameters
*/
mov x0, xzr
mov x1, xzr
mov x2, xzr
mov x3, xzr
mrs x4, mpidr_el1
tst x4, #15
b.eq 2f
/*
* Secondary CPUs
*/
1: wfe
ldr x4, mbox
cbz x4, 1b
br x4 // branch to the given address
2:
/*
* UART initialisation (38400 8N1)
*/
ldr x4, =UART_BASE // UART base
mov w5, #0x10 // ibrd
str w5, [x4, #0x24]
mov w5, #0xc300
orr w5, w5, #0x0001 // cr
str w5, [x4, #0x30]
/*
* Primary CPU
*/
ldr x0, =dtb // device tree blob
b kernel
.ltorg
.org 0x200
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