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>master
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3a592a1349
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/*
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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 <common.h> |
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#include <libfdt.h> |
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#include <asm/spin_table.h> |
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int spin_table_update_dt(void *fdt) |
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{ |
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int cpus_offset, offset; |
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const char *prop; |
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int ret; |
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unsigned long rsv_addr = (unsigned long)&spin_table_reserve_begin; |
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unsigned long rsv_size = &spin_table_reserve_end - |
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&spin_table_reserve_begin; |
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cpus_offset = fdt_path_offset(fdt, "/cpus"); |
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if (cpus_offset < 0) |
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return -ENODEV; |
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for (offset = fdt_first_subnode(fdt, cpus_offset); |
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offset >= 0; |
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offset = fdt_next_subnode(fdt, offset)) { |
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prop = fdt_getprop(fdt, offset, "device_type", NULL); |
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if (!prop || strcmp(prop, "cpu")) |
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continue; |
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/*
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* In the first loop, we check if every CPU node specifies |
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* spin-table. Otherwise, just return successfully to not |
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* disturb other methods, like psci. |
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*/ |
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prop = fdt_getprop(fdt, offset, "enable-method", NULL); |
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if (!prop || strcmp(prop, "spin-table")) |
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return 0; |
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} |
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for (offset = fdt_first_subnode(fdt, cpus_offset); |
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offset >= 0; |
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offset = fdt_next_subnode(fdt, offset)) { |
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prop = fdt_getprop(fdt, offset, "device_type", NULL); |
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if (!prop || strcmp(prop, "cpu")) |
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continue; |
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ret = fdt_setprop_u64(fdt, offset, "cpu-release-addr", |
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(unsigned long)&spin_table_cpu_release_addr); |
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if (ret) |
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return -ENOSPC; |
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} |
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ret = fdt_add_mem_rsv(fdt, rsv_addr, rsv_size); |
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if (ret) |
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return -ENOSPC; |
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printf(" Reserved memory region for spin-table: addr=%lx size=%lx\n", |
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rsv_addr, rsv_size); |
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return 0; |
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} |
@ -0,0 +1,23 @@ |
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/* |
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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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/*
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* SPDX-License-Identifier: GPL-2.0+ |
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*/ |
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#ifndef __ASM_SPIN_TABLE_H__ |
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#define __ASM_SPIN_TABLE_H__ |
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extern u64 spin_table_cpu_release_addr; |
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extern char spin_table_reserve_begin; |
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extern char spin_table_reserve_end; |
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int spin_table_update_dt(void *fdt); |
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#endif /* __ASM_SPIN_TABLE_H__ */ |
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