Unverified Commit 2d268251 authored by Palmer Dabbelt's avatar Palmer Dabbelt
Browse files

riscv: Allow device trees to be built into the kernel 



Some systems don't provide a useful device tree to the kernel on boot.
Chasing around bootloaders for these systems is a headache, so instead
le't's just keep a device tree table in the kernel, keyed by the SOC's
unique identifier, that contains the relevant DTB.

This is only implemented for M mode right now. While we could implement
this via the SBI calls that allow access to these identifiers, we don't
have any systems that need this right now.

Signed-off-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
parent b9bbe6ed

arch/riscv/Kbuild

+1 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0-only



obj-y += kernel/ mm/ net/

obj-$(CONFIG_BUILTIN_DTB) += boot/dts/

arch/riscv/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -381,6 +381,11 @@ endchoice 


endmenu



config BUILTIN_DTB

	def_bool n

	depends on RISCV_M_MODE

	depends on OF



menu "Power management options"



source "kernel/power/Kconfig"

arch/riscv/include/asm/soc.h

+39 −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.

 * Copyright (C) 2020 Google, Inc

 */



#ifndef _ASM_RISCV_SOC_H
@@ -20,4 +21,42 @@ void soc_early_init(void); 
extern unsigned long __soc_early_init_table_start;

extern unsigned long __soc_early_init_table_end;



/*

 * Allows Linux to provide a device tree, which is necessary for SOCs that

 * don't provide a useful one on their own.

 */

struct soc_builtin_dtb {

	unsigned long vendor_id;

	unsigned long arch_id;

	unsigned long imp_id;

	void *(*dtb_func)(void);

};



/*

 * The argument name must specify a valid DTS file name without the dts

 * extension.

 */

#define SOC_BUILTIN_DTB_DECLARE(name, vendor, arch, impl)		\

	extern void *__dtb_##name##_begin;				\

									\

	static __init __used						\

	void *__soc_builtin_dtb_f__##name(void)				\

	{								\

		return (void *)&__dtb_##name##_begin;			\

	}								\

									\

	static const struct soc_builtin_dtb __soc_builtin_dtb__##name	\

		__used __section(__soc_builtin_dtb_table) =		\

	{								\

		.vendor_id = vendor,					\

		.arch_id   = arch,					\

		.imp_id    = impl,					\

		.dtb_func  = __soc_builtin_dtb_f__##name,		\

	}



extern unsigned long __soc_builtin_dtb_table_start;

extern unsigned long __soc_builtin_dtb_table_end;



void *soc_lookup_builtin_dtb(void);



#endif

arch/riscv/kernel/setup.c

+4 −0
Original line number Diff line number Diff line
@@ -75,7 +75,11 @@ void __init setup_arch(char **cmdline_p) 


	setup_bootmem();

	paging_init();

#if IS_ENABLED(CONFIG_BUILTIN_DTB)

	unflatten_and_copy_device_tree();

#else

	unflatten_device_tree();

#endif

	clint_init_boot_cpu();



#ifdef CONFIG_SWIOTLB

arch/riscv/kernel/soc.c

+27 −0
Original line number Diff line number Diff line
@@ -26,3 +26,30 @@ void __init soc_early_init(void) 
		}

	}

}



static bool soc_builtin_dtb_match(unsigned long vendor_id,

				unsigned long arch_id, unsigned long imp_id,

				const struct soc_builtin_dtb *entry)

{

	return entry->vendor_id == vendor_id &&

	       entry->arch_id == arch_id &&

	       entry->imp_id == imp_id;

}



void * __init soc_lookup_builtin_dtb(void)

{

	unsigned long vendor_id, arch_id, imp_id;

	const struct soc_builtin_dtb *s;



	__asm__ ("csrr %0, mvendorid" : "=r"(vendor_id));

	__asm__ ("csrr %0, marchid" : "=r"(arch_id));

	__asm__ ("csrr %0, mimpid" : "=r"(imp_id));



	for (s = (void *)&__soc_builtin_dtb_table_start;

	     (void *)s < (void *)&__soc_builtin_dtb_table_end; s++) {

		if (soc_builtin_dtb_match(vendor_id, arch_id, imp_id, s))

			return s->dtb_func();

	}



	return NULL;

}

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