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There are two enable methods supported by ARM64 Linux; psci and
spin-table. The latter is simpler and helpful for quick SoC bring
up. My main motivation for this patch is to improve the spin-table
support, which allows us to boot an ARMv8 system without the ARM
Trusted Firmware.
Currently, we have multi-entry code in arch/arm/cpu/armv8/start.S
and the spin-table is supported in a really ad-hoc way, and I see
some problems:
- We must hard-code CPU_RELEASE_ADDR so that it matches the
"cpu-release-addr" property in the DT that comes from the
kernel tree.
- The Documentation/arm64/booting.txt in Linux requires that
the release address must be zero-initialized, but it is not
cared by the common code in U-Boot. We must do it in a board
function.
- There is no systematic way to protect the spin-table code from
the kernel. We are supposed to do it in a board specific manner,
but it is difficult to predict where the spin-table code will be
located after the relocation. So, it also makes difficult to
hard-code /memreserve/ in the DT of the kernel.
So, here is a patch to solve those problems; the DT is run-time
modified to reserve the spin-table code (+ cpu-release-addr).
Also, the "cpu-release-addr" property is set to an appropriate
address after the relocation, which means we no longer need the
hard-coded CPU_RELEASE_ADDR.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
24 lines
500 B
ArmAsm
24 lines
500 B
ArmAsm
/*
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* Copyright (C) 2016 Socionext Inc.
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* Author: Masahiro Yamada <yamada.masahiro@socionext.com>
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#include <linux/linkage.h>
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ENTRY(spin_table_secondary_jump)
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.globl spin_table_reserve_begin
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spin_table_reserve_begin:
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0: wfe
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ldr x0, spin_table_cpu_release_addr
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cbz x0, 0b
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br x0
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.globl spin_table_cpu_release_addr
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.align 3
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spin_table_cpu_release_addr:
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.quad 0
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.globl spin_table_reserve_end
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spin_table_reserve_end:
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ENDPROC(spin_table_secondary_jump)
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