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

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

arch/riscv/include/asm/soc.h

0 → 100644
+23 −0
Original line number Diff line number Diff line 
/* 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

arch/riscv/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ endif 
extra-y += head.o

extra-y += vmlinux.lds



obj-y	+= soc.o

obj-y	+= cpu.o

obj-y	+= cpufeature.o

obj-y	+= entry.o

arch/riscv/kernel/head.S

+1 −0
Original line number Diff line number Diff line
@@ -234,6 +234,7 @@ clear_bss_done: 
	call kasan_early_init

#endif

	/* Start the kernel */

	call soc_early_init

	call parse_dtb

	tail start_kernel

arch/riscv/kernel/soc.c

0 → 100644
+28 −0
Original line number Diff line number Diff line 
// 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;

		}

	}

}

arch/riscv/kernel/vmlinux.lds.S

+6 −0
Original line number Diff line number Diff line
@@ -28,6 +28,12 @@ SECTIONS 
	__init_begin = .;

	INIT_TEXT_SECTION(PAGE_SIZE)

	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 */

	.exit.text :

	{

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