Opensbi笔记

/*
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2019 Western Digital Corporation or its affiliates.
 *
 * Authors:
 *   Anup Patel <anup.patel@wdc.com>
 */

	. = FW_TEXT_START;
	/* Don't add any section between FW_TEXT_START and _fw_start */
	PROVIDE(_fw_start = .);

	. = ALIGN(0x1000); /* Need this to create proper sections */

	/* Beginning of the code section */

	.text :
 	{
		PROVIDE(_text_start = .);
		*(.entry)
		*(.text)
		. = ALIGN(8);
		PROVIDE(_text_end = .);
	}

	. = ALIGN(0x1000); /* Ensure next section is page aligned */

	/* End of the code sections */

	/* Beginning of the read-only data sections */

	. = ALIGN(0x1000); /* Ensure next section is page aligned */

	.rodata :
	{
		PROVIDE(_rodata_start = .);
		*(.rodata .rodata.*)
		. = ALIGN(8);
		PROVIDE(_rodata_end = .);
	}

	/* End of the read-only data sections */

	/* Beginning of the read-write data sections */

	. = ALIGN(0x1000); /* Ensure next section is page aligned */

	.data :
	{
		PROVIDE(_data_start = .);

		*(.sdata)
		*(.sdata.*)
		*(.data)
		*(.data.*)
		*(.readmostly.data)
		*(*.data)
		. = ALIGN(8);

		PROVIDE(_data_end = .);
	}

	.dynsym : {
		PROVIDE(__dyn_sym_start = .);
		*(.dynsym)
		PROVIDE(__dyn_sym_end = .);
	}

	.rela.dyn : {
		PROVIDE(__rel_dyn_start = .);
		*(.rela*)
		. = ALIGN(8);
		PROVIDE(__rel_dyn_end = .);
	}

	. = ALIGN(0x1000); /* Ensure next section is page aligned */

	.bss :
	{
		PROVIDE(_bss_start = .);
		*(.sbss)
		*(.sbss.*)
		*(.bss)
		*(.bss.*)
		. = ALIGN(8);
		PROVIDE(_bss_end = .);
	}

	/* End of the read-write data sections */

	. = ALIGN(0x1000); /* Need this to create proper sections */

	PROVIDE(_fw_end = .);

_start:
	/* Find preferred boot HART id */
	MOV_3R	s0, a0, s1, a1, s2, a2
	call	fw_boot_hart
	add	a6, a0, zero
	MOV_3R	a0, s0, a1, s1, a2, s2
	li	a7, -1
	beq	a6, a7, _try_lottery
	/* Jump to relocation wait loop if we are not boot hart */
	bne	a0, a6, _wait_relocate_copy_done

_wait_for_boot_hart:
	li	t0, BOOT_STATUS_BOOT_HART_DONE
	lla	t1, _boot_status
	REG_L	t1, 0(t1)
	/* Reduce the bus traffic so that boot hart may proceed faster */
	nop
	nop
	nop
	bne	t0, t1, _wait_for_boot_hart

#ifdef FW_PIN
        ....
#else:
	/* Relocate if load address != link address */
_relocate:
	lla	t0, _link_start
	REG_L	t0, 0(t0)
	lla	t1, _link_end
	REG_L	t1, 0(t1)
	lla	t2, _load_start
	REG_L	t2, 0(t2)
	sub	t3, t1, t0
	add	t3, t3, t2
	beq	t0, t2, _relocate_done//地址相同,不用做
	lla	t4, _relocate_done
	sub	t4, t4, t2
	add	t4, t4, t0
	blt	t2, t0, _relocate_copy_to_upper//不同,直接开始移动

_relocate_done:

	/*
	 * Mark relocate copy done
	 * Use _boot_status copy relative to the load address
	 */
	lla	t0, _boot_status
#ifndef FW_PIC
	lla	t1, _link_start
	REG_L	t1, 0(t1)
	lla	t2, _load_start
	REG_L	t2, 0(t2)
	sub	t0, t0, t1
	add	t0, t0, t2
#endif
	li	t1, BOOT_STATUS_RELOCATE_DONE
	REG_S	t1, 0(t0)
	fence	rw, rw

	/* At this point we are running from link address */

	/* Reset all registers for boot HART */
	li	ra, 0
	call	_reset_regs

	/* Zero-out BSS */
	lla	s4, _bss_start
	lla	s5, _bss_end

_bss_zero:
	REG_S	zero, (s4)
	add	s4, s4, __SIZEOF_POINTER__
	blt	s4, s5, _bss_zero

	/* Setup temporary trap handler */
	lla	s4, _start_hang
	csrw	CSR_MTVEC, s4

	/* Setup temporary stack */
	lla	s4, _fw_end
	li	s5, (SBI_SCRATCH_SIZE * 2)
	add	sp, s4, s5

	/* Allow main firmware to save info */
	MOV_5R	s0, a0, s1, a1, s2, a2, s3, a3, s4, a4
	call	fw_save_info
	MOV_5R	a0, s0, a1, s1, a2, s2, a3, s3, a4, s4

#ifdef FW_FDT_PATH
	/* Override previous arg1 */
	lla	a1, fw_fdt_bin
#endif

	/*
	 * Initialize platform
	 * Note: The a0 to a4 registers passed to the
	 * firmware are parameters to this function.
	 */
	MOV_5R	s0, a0, s1, a1, s2, a2, s3, a3, s4, a4
	call	fw_platform_init
	add	t0, a0, zero
	MOV_5R	a0, s0, a1, s1, a2, s2, a3, s3, a4, s4
	add	a1, t0, zero

	/* Preload HART details
	 * s7 -> HART Count
	 * s8 -> HART Stack Size
	 */
	lla	a4, platform

_fdt_reloc_again:
	REG_L	t3, 0(t0)
	REG_S	t3, 0(t1)
	add	t0, t0, __SIZEOF_POINTER__
	add	t1, t1, __SIZEOF_POINTER__
	blt	t1, t2, _fdt_reloc_again
_fdt_reloc_done:

	/* mark boot hart done */
	li	t0, BOOT_STATUS_BOOT_HART_DONE
	lla	t1, _boot_status
	REG_S	t0, 0(t1)
	fence	rw, rw
	j	_start_warm

const struct sbi_platform_operations platform_ops = {
	.nascent_init		= generic_nascent_init,
	.early_init		= generic_early_init,
	.final_init		= generic_final_init,
	.early_exit		= generic_early_exit,
	.final_exit		= generic_final_exit,
	.domains_init		= generic_domains_init,
	.console_init		= fdt_serial_init,
	.irqchip_init		= fdt_irqchip_init,
	.irqchip_exit		= fdt_irqchip_exit,
	.ipi_init		= fdt_ipi_init,
	.ipi_exit		= fdt_ipi_exit,
	.pmu_init		= generic_pmu_init,
	.pmu_xlate_to_mhpmevent = generic_pmu_xlate_to_mhpmevent,
	.get_tlbr_flush_limit	= generic_tlbr_flush_limit,
	.timer_init		= fdt_timer_init,
	.timer_exit		= fdt_timer_exit,
};

struct sbi_platform platform = {
	.opensbi_version	= OPENSBI_VERSION,
	.platform_version	= SBI_PLATFORM_VERSION(0x0, 0x01),
	.name			= "Generic",
	.features		= SBI_PLATFORM_DEFAULT_FEATURES,
	.hart_count		= SBI_HARTMASK_MAX_BITS,
	.hart_index2id		= generic_hart_index2id,
	.hart_stack_size	= SBI_PLATFORM_DEFAULT_HART_STACK_SIZE,
	.platform_ops_addr	= (unsigned long)&platform_ops
};
//在sifive_fu740.c中有这个定义,在genetic中我们就是调用这个结构题对platform结构体进行修改的.
const struct platform_override sifive_fu740 = {
	.match_table = sifive_fu740_match,
	.tlbr_flush_limit = sifive_fu740_tlbr_flush_limit,
	.final_init = sifive_fu740_final_init,
};

        fw_platform_lookup_special(fdt, root_offset);

	model = fdt_getprop(fdt, root_offset, "model", &len);
	if (model)
		sbi_strncpy(platform.name, model, sizeof(platform.name) - 1);

	if (generic_plat && generic_plat->features)
		platform.features = generic_plat->features(generic_plat_match);