mirror of
https://github.com/AsahiLinux/u-boot
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68f08966b0
There is some code that tries to "reset" the SCTLR_ELx register early in
the boot process. The idea seems to be to guarantee some sane settings
that U-Boot actually relies on, for instance running in little-endian
mode, with the MMU off initially.
However the current code has multiple problems:
- For a start, no platform or config defines the symbol that would
enable that code.
- The code itself really only works if the bits that it tries to clear
are already cleared:
- If we run in big-endian mode initially, any previous loads would have
been wrong already. That applies to the (optional) relocation code,
but more prominently to the mask that it uses to clear those bits:
"ldr x1, =0xfdfffffa" looks innocent, but actually involves a memory
access to the literal pool, using the current endianness.
- If we run with the MMU enabled, we are probably doomed already. We
*could* hope that we are running with an identity mapping, but would
need to do some cache maintenance to avoid losing dirty cache lines.
- The idea of doing a read-modify-write of SCTLR is somewhat
questionable to begin with, because as the owner of the current
exception level we should initialise all bits of this register with a
certain fixed value.
- The code is unnecessarily complicated, and the function name is
misspelled.
While those problems *could* admittedly be fixed, the point that is does
not seem to be used at all at the moment tells me we should just remove
this code, and be it to not give a bad example.
If people care, I could introduce some proper SCTLR initialisation code.
We are about to work this out for the boot-wrapper[1] as we speak, but
apparently we got away without doing this in U-Boot ever since, so it
might not be worth the potential trouble.
[1] https://lore.kernel.org/linux-arm-kernel/20220114105653.3003399-7-mark.rutland@arm.com/
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
370 lines
8.3 KiB
ArmAsm
370 lines
8.3 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* (C) Copyright 2013
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* David Feng <fenghua@phytium.com.cn>
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*/
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#include <asm-offsets.h>
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#include <config.h>
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#include <linux/linkage.h>
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#include <asm/macro.h>
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#include <asm/armv8/mmu.h>
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/*************************************************************************
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*
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* Startup Code (reset vector)
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*
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*************************************************************************/
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.globl _start
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_start:
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#if defined(CONFIG_LINUX_KERNEL_IMAGE_HEADER)
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#include <asm/boot0-linux-kernel-header.h>
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#elif defined(CONFIG_ENABLE_ARM_SOC_BOOT0_HOOK)
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/*
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* Various SoCs need something special and SoC-specific up front in
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* order to boot, allow them to set that in their boot0.h file and then
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* use it here.
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*/
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#include <asm/arch/boot0.h>
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#else
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b reset
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#endif
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.align 3
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.globl _TEXT_BASE
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_TEXT_BASE:
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.quad CONFIG_SYS_TEXT_BASE
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/*
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* These are defined in the linker script.
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*/
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.globl _end_ofs
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_end_ofs:
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.quad _end - _start
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.globl _bss_start_ofs
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_bss_start_ofs:
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.quad __bss_start - _start
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.globl _bss_end_ofs
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_bss_end_ofs:
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.quad __bss_end - _start
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reset:
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/* Allow the board to save important registers */
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b save_boot_params
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.globl save_boot_params_ret
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save_boot_params_ret:
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#if CONFIG_POSITION_INDEPENDENT
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/* Verify that we're 4K aligned. */
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adr x0, _start
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ands x0, x0, #0xfff
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b.eq 1f
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0:
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/*
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* FATAL, can't continue.
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* U-Boot needs to be loaded at a 4K aligned address.
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*
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* We use ADRP and ADD to load some symbol addresses during startup.
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* The ADD uses an absolute (non pc-relative) lo12 relocation
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* thus requiring 4K alignment.
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*/
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wfi
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b 0b
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1:
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/*
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* Fix .rela.dyn relocations. This allows U-Boot to be loaded to and
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* executed at a different address than it was linked at.
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*/
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pie_fixup:
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adr x0, _start /* x0 <- Runtime value of _start */
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ldr x1, _TEXT_BASE /* x1 <- Linked value of _start */
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subs x9, x0, x1 /* x9 <- Run-vs-link offset */
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beq pie_fixup_done
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adrp x2, __rel_dyn_start /* x2 <- Runtime &__rel_dyn_start */
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add x2, x2, #:lo12:__rel_dyn_start
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adrp x3, __rel_dyn_end /* x3 <- Runtime &__rel_dyn_end */
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add x3, x3, #:lo12:__rel_dyn_end
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pie_fix_loop:
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ldp x0, x1, [x2], #16 /* (x0, x1) <- (Link location, fixup) */
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ldr x4, [x2], #8 /* x4 <- addend */
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cmp w1, #1027 /* relative fixup? */
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bne pie_skip_reloc
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/* relative fix: store addend plus offset at dest location */
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add x0, x0, x9
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add x4, x4, x9
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str x4, [x0]
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pie_skip_reloc:
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cmp x2, x3
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b.lo pie_fix_loop
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pie_fixup_done:
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#endif
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#if defined(CONFIG_ARMV8_SPL_EXCEPTION_VECTORS) || !defined(CONFIG_SPL_BUILD)
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.macro set_vbar, regname, reg
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msr \regname, \reg
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.endm
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adr x0, vectors
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#else
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.macro set_vbar, regname, reg
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.endm
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#endif
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/*
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* Could be EL3/EL2/EL1, Initial State:
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* Little Endian, MMU Disabled, i/dCache Disabled
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*/
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switch_el x1, 3f, 2f, 1f
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3: set_vbar vbar_el3, x0
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mrs x0, scr_el3
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orr x0, x0, #0xf /* SCR_EL3.NS|IRQ|FIQ|EA */
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msr scr_el3, x0
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msr cptr_el3, xzr /* Enable FP/SIMD */
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b 0f
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2: mrs x1, hcr_el2
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tbnz x1, #34, 1f /* HCR_EL2.E2H */
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set_vbar vbar_el2, x0
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mov x0, #0x33ff
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msr cptr_el2, x0 /* Enable FP/SIMD */
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b 0f
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1: set_vbar vbar_el1, x0
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mov x0, #3 << 20
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msr cpacr_el1, x0 /* Enable FP/SIMD */
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0:
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#ifdef COUNTER_FREQUENCY
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branch_if_not_highest_el x0, 4f
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ldr x0, =COUNTER_FREQUENCY
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msr cntfrq_el0, x0 /* Initialize CNTFRQ */
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#endif
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4: isb
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/*
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* Enable SMPEN bit for coherency.
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* This register is not architectural but at the moment
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* this bit should be set for A53/A57/A72.
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*/
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#ifdef CONFIG_ARMV8_SET_SMPEN
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switch_el x1, 3f, 1f, 1f
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3:
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mrs x0, S3_1_c15_c2_1 /* cpuectlr_el1 */
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orr x0, x0, #0x40
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msr S3_1_c15_c2_1, x0
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isb
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1:
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#endif
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/* Apply ARM core specific erratas */
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bl apply_core_errata
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/*
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* Cache/BPB/TLB Invalidate
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* i-cache is invalidated before enabled in icache_enable()
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* tlb is invalidated before mmu is enabled in dcache_enable()
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* d-cache is invalidated before enabled in dcache_enable()
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*/
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/* Processor specific initialization */
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bl lowlevel_init
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#if defined(CONFIG_ARMV8_SPIN_TABLE) && !defined(CONFIG_SPL_BUILD)
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branch_if_master x0, x1, master_cpu
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b spin_table_secondary_jump
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/* never return */
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#elif defined(CONFIG_ARMV8_MULTIENTRY)
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branch_if_master x0, x1, master_cpu
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/*
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* Slave CPUs
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*/
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slave_cpu:
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wfe
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ldr x1, =CPU_RELEASE_ADDR
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ldr x0, [x1]
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cbz x0, slave_cpu
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br x0 /* branch to the given address */
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#endif /* CONFIG_ARMV8_MULTIENTRY */
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master_cpu:
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bl _main
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/*-----------------------------------------------------------------------*/
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WEAK(apply_core_errata)
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mov x29, lr /* Save LR */
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/* For now, we support Cortex-A53, Cortex-A57 specific errata */
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/* Check if we are running on a Cortex-A53 core */
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branch_if_a53_core x0, apply_a53_core_errata
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/* Check if we are running on a Cortex-A57 core */
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branch_if_a57_core x0, apply_a57_core_errata
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0:
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mov lr, x29 /* Restore LR */
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ret
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apply_a53_core_errata:
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#ifdef CONFIG_ARM_ERRATA_855873
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mrs x0, midr_el1
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tst x0, #(0xf << 20)
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b.ne 0b
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mrs x0, midr_el1
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and x0, x0, #0xf
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cmp x0, #3
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b.lt 0b
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mrs x0, S3_1_c15_c2_0 /* cpuactlr_el1 */
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/* Enable data cache clean as data cache clean/invalidate */
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orr x0, x0, #1 << 44
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msr S3_1_c15_c2_0, x0 /* cpuactlr_el1 */
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isb
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#endif
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b 0b
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apply_a57_core_errata:
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#ifdef CONFIG_ARM_ERRATA_828024
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mrs x0, S3_1_c15_c2_0 /* cpuactlr_el1 */
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/* Disable non-allocate hint of w-b-n-a memory type */
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orr x0, x0, #1 << 49
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/* Disable write streaming no L1-allocate threshold */
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orr x0, x0, #3 << 25
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/* Disable write streaming no-allocate threshold */
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orr x0, x0, #3 << 27
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msr S3_1_c15_c2_0, x0 /* cpuactlr_el1 */
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isb
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#endif
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#ifdef CONFIG_ARM_ERRATA_826974
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mrs x0, S3_1_c15_c2_0 /* cpuactlr_el1 */
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/* Disable speculative load execution ahead of a DMB */
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orr x0, x0, #1 << 59
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msr S3_1_c15_c2_0, x0 /* cpuactlr_el1 */
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isb
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#endif
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#ifdef CONFIG_ARM_ERRATA_833471
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mrs x0, S3_1_c15_c2_0 /* cpuactlr_el1 */
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/* FPSCR write flush.
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* Note that in some cases where a flush is unnecessary this
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could impact performance. */
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orr x0, x0, #1 << 38
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msr S3_1_c15_c2_0, x0 /* cpuactlr_el1 */
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isb
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#endif
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#ifdef CONFIG_ARM_ERRATA_829520
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mrs x0, S3_1_c15_c2_0 /* cpuactlr_el1 */
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/* Disable Indirect Predictor bit will prevent this erratum
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from occurring
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* Note that in some cases where a flush is unnecessary this
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could impact performance. */
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orr x0, x0, #1 << 4
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msr S3_1_c15_c2_0, x0 /* cpuactlr_el1 */
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isb
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#endif
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#ifdef CONFIG_ARM_ERRATA_833069
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mrs x0, S3_1_c15_c2_0 /* cpuactlr_el1 */
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/* Disable Enable Invalidates of BTB bit */
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and x0, x0, #0xE
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msr S3_1_c15_c2_0, x0 /* cpuactlr_el1 */
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isb
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#endif
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b 0b
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ENDPROC(apply_core_errata)
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/*-----------------------------------------------------------------------*/
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WEAK(lowlevel_init)
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mov x29, lr /* Save LR */
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#if defined(CONFIG_GICV2) || defined(CONFIG_GICV3)
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branch_if_slave x0, 1f
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ldr x0, =GICD_BASE
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bl gic_init_secure
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1:
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#if defined(CONFIG_GICV3)
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ldr x0, =GICR_BASE
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bl gic_init_secure_percpu
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#elif defined(CONFIG_GICV2)
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ldr x0, =GICD_BASE
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ldr x1, =GICC_BASE
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bl gic_init_secure_percpu
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#endif
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#endif
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#ifdef CONFIG_ARMV8_MULTIENTRY
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branch_if_master x0, x1, 2f
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/*
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* Slave should wait for master clearing spin table.
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* This sync prevent salves observing incorrect
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* value of spin table and jumping to wrong place.
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*/
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#if defined(CONFIG_GICV2) || defined(CONFIG_GICV3)
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#ifdef CONFIG_GICV2
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ldr x0, =GICC_BASE
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#endif
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bl gic_wait_for_interrupt
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#endif
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/*
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* All slaves will enter EL2 and optionally EL1.
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*/
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adr x4, lowlevel_in_el2
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ldr x5, =ES_TO_AARCH64
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bl armv8_switch_to_el2
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lowlevel_in_el2:
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#ifdef CONFIG_ARMV8_SWITCH_TO_EL1
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adr x4, lowlevel_in_el1
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ldr x5, =ES_TO_AARCH64
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bl armv8_switch_to_el1
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lowlevel_in_el1:
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#endif
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#endif /* CONFIG_ARMV8_MULTIENTRY */
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2:
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mov lr, x29 /* Restore LR */
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ret
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ENDPROC(lowlevel_init)
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WEAK(smp_kick_all_cpus)
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/* Kick secondary cpus up by SGI 0 interrupt */
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#if defined(CONFIG_GICV2) || defined(CONFIG_GICV3)
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ldr x0, =GICD_BASE
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b gic_kick_secondary_cpus
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#endif
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ret
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ENDPROC(smp_kick_all_cpus)
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/*-----------------------------------------------------------------------*/
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ENTRY(c_runtime_cpu_setup)
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#if defined(CONFIG_ARMV8_SPL_EXCEPTION_VECTORS) || !defined(CONFIG_SPL_BUILD)
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/* Relocate vBAR */
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adr x0, vectors
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switch_el x1, 3f, 2f, 1f
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3: msr vbar_el3, x0
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b 0f
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2: msr vbar_el2, x0
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b 0f
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1: msr vbar_el1, x0
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0:
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#endif
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ret
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ENDPROC(c_runtime_cpu_setup)
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WEAK(save_boot_params)
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b save_boot_params_ret /* back to my caller */
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ENDPROC(save_boot_params)
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