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riscv: Add SOC early init support
Add a mechanism for early SoC initialization for platforms that need additional hardware initialization not possible through the regular device tree and drivers mechanism. With this, a SoC specific initialization function can be called very early, before DTB parsing is done by parse_dtb() in Linux RISC-V kernel setup code. This can be very useful for early hardware initialization for No-MMU kernels booted directly in M-mode because it is quite likely that no other booting stage exist prior to the No-MMU kernel. Example use of a SoC early initialization is as follows: static void vendor_abc_early_init(const void *fdt) { /* * some early init code here that can use simple matches * against the flat device tree file. */ } SOC_EARLY_INIT_DECLARE("vendor,abc", abc_early_init); This early initialization function is executed only if the flat device tree for the board has a 'compatible = "vendor,abc"' entry; Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Anup Patel <anup.patel@wdc.com> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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5 changed files with 59 additions and 0 deletions
23
arch/riscv/include/asm/soc.h
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23
arch/riscv/include/asm/soc.h
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@ -0,0 +1,23 @@
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/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* Copyright (C) 2020 Western Digital Corporation or its affiliates.
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*/
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#ifndef _ASM_RISCV_SOC_H
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#define _ASM_RISCV_SOC_H
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#include <linux/of.h>
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#include <linux/linkage.h>
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#include <linux/types.h>
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#define SOC_EARLY_INIT_DECLARE(name, compat, fn) \
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static const struct of_device_id __soc_early_init__##name \
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__used __section(__soc_early_init_table) \
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= { .compatible = compat, .data = fn }
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void soc_early_init(void);
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extern unsigned long __soc_early_init_table_start;
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extern unsigned long __soc_early_init_table_end;
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#endif
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@ -11,6 +11,7 @@ endif
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extra-y += head.o
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extra-y += head.o
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extra-y += vmlinux.lds
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extra-y += vmlinux.lds
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obj-y += soc.o
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obj-y += cpu.o
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obj-y += cpu.o
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obj-y += cpufeature.o
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obj-y += cpufeature.o
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obj-y += entry.o
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obj-y += entry.o
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@ -234,6 +234,7 @@ clear_bss_done:
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call kasan_early_init
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call kasan_early_init
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#endif
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#endif
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/* Start the kernel */
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/* Start the kernel */
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call soc_early_init
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call parse_dtb
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call parse_dtb
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tail start_kernel
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tail start_kernel
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28
arch/riscv/kernel/soc.c
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arch/riscv/kernel/soc.c
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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2020 Western Digital Corporation or its affiliates.
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*/
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#include <linux/init.h>
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#include <linux/libfdt.h>
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#include <asm/pgtable.h>
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#include <asm/soc.h>
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/*
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* This is called extremly early, before parse_dtb(), to allow initializing
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* SoC hardware before memory or any device driver initialization.
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*/
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void __init soc_early_init(void)
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{
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void (*early_fn)(const void *fdt);
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const struct of_device_id *s;
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const void *fdt = dtb_early_va;
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for (s = (void *)&__soc_early_init_table_start;
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(void *)s < (void *)&__soc_early_init_table_end; s++) {
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if (!fdt_node_check_compatible(fdt, 0, s->compatible)) {
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early_fn = s->data;
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early_fn(fdt);
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return;
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}
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}
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}
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@ -28,6 +28,12 @@ SECTIONS
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__init_begin = .;
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__init_begin = .;
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INIT_TEXT_SECTION(PAGE_SIZE)
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INIT_TEXT_SECTION(PAGE_SIZE)
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INIT_DATA_SECTION(16)
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INIT_DATA_SECTION(16)
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. = ALIGN(8);
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__soc_early_init_table : {
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__soc_early_init_table_start = .;
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KEEP(*(__soc_early_init_table))
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__soc_early_init_table_end = .;
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}
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/* we have to discard exit text and such at runtime, not link time */
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/* we have to discard exit text and such at runtime, not link time */
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.exit.text :
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.exit.text :
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{
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{
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