Commit 335b1390 authored by Damien Le Moal's avatar Damien Le Moal Committed by Palmer Dabbelt

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: default avatarDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: default avatarAnup Patel <anup.patel@wdc.com>
Signed-off-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
parent 956d705d
/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Copyright (C) 2020 Western Digital Corporation or its affiliates.
*/
#ifndef _ASM_RISCV_SOC_H
#define _ASM_RISCV_SOC_H
#include <linux/of.h>
#include <linux/linkage.h>
#include <linux/types.h>
#define SOC_EARLY_INIT_DECLARE(name, compat, fn) \
static const struct of_device_id __soc_early_init__##name \
__used __section(__soc_early_init_table) \
= { .compatible = compat, .data = fn }
void soc_early_init(void);
extern unsigned long __soc_early_init_table_start;
extern unsigned long __soc_early_init_table_end;
#endif
...@@ -11,6 +11,7 @@ endif ...@@ -11,6 +11,7 @@ endif
extra-y += head.o extra-y += head.o
extra-y += vmlinux.lds extra-y += vmlinux.lds
obj-y += soc.o
obj-y += cpu.o obj-y += cpu.o
obj-y += cpufeature.o obj-y += cpufeature.o
obj-y += entry.o obj-y += entry.o
......
...@@ -234,6 +234,7 @@ clear_bss_done: ...@@ -234,6 +234,7 @@ clear_bss_done:
call kasan_early_init call kasan_early_init
#endif #endif
/* Start the kernel */ /* Start the kernel */
call soc_early_init
call parse_dtb call parse_dtb
tail start_kernel tail start_kernel
......
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2020 Western Digital Corporation or its affiliates.
*/
#include <linux/init.h>
#include <linux/libfdt.h>
#include <asm/pgtable.h>
#include <asm/soc.h>
/*
* This is called extremly early, before parse_dtb(), to allow initializing
* SoC hardware before memory or any device driver initialization.
*/
void __init soc_early_init(void)
{
void (*early_fn)(const void *fdt);
const struct of_device_id *s;
const void *fdt = dtb_early_va;
for (s = (void *)&__soc_early_init_table_start;
(void *)s < (void *)&__soc_early_init_table_end; s++) {
if (!fdt_node_check_compatible(fdt, 0, s->compatible)) {
early_fn = s->data;
early_fn(fdt);
return;
}
}
}
...@@ -28,6 +28,12 @@ SECTIONS ...@@ -28,6 +28,12 @@ SECTIONS
__init_begin = .; __init_begin = .;
INIT_TEXT_SECTION(PAGE_SIZE) INIT_TEXT_SECTION(PAGE_SIZE)
INIT_DATA_SECTION(16) INIT_DATA_SECTION(16)
. = ALIGN(8);
__soc_early_init_table : {
__soc_early_init_table_start = .;
KEEP(*(__soc_early_init_table))
__soc_early_init_table_end = .;
}
/* we have to discard exit text and such at runtime, not link time */ /* we have to discard exit text and such at runtime, not link time */
.exit.text : .exit.text :
{ {
......
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