第二个函数

<span style="font-size:14px;">void arch_early_init(void)
{
	/* turn off the cache */
	arch_disable_cache(UCACHE);

	/* set the vector base to our exception vectors so we dont need to double map at 0 */
#if ARM_CPU_CORTEX_A8
	set_vector_base(MEMBASE);
#endif

#if ARM_WITH_MMU
	arm_mmu_init();

#endif

	/* turn the cache back on */
	arch_enable_cache(UCACHE);

#if ARM_WITH_NEON
	/* enable cp10 and cp11 */
	uint32_t val;
	__asm__ volatile("mrc	p15, 0, %0, c1, c0, 2" : "=r" (val));
	val |= (3<<22)|(3<<20);
	__asm__ volatile("mcr	p15, 0, %0, c1, c0, 2" :: "r" (val));

	/* set enable bit in fpexc */
	__asm__ volatile("mrc  p10, 7, %0, c8, c0, 0" : "=r" (val));
	val |= (1<<30);
	__asm__ volatile("mcr  p10, 7, %0, c8, c0, 0" :: "r" (val));
#endif

#if ARM_CPU_CORTEX_A8
	/* enable the cycle count register */
	uint32_t en;
	__asm__ volatile("mrc	p15, 0, %0, c9, c12, 0" : "=r" (en));
	en &= ~(1<<3); /* cycle count every cycle */
	en |= 1; /* enable all performance counters */
	__asm__ volatile("mcr	p15, 0, %0, c9, c12, 0" :: "r" (en));

	/* enable cycle counter */
	en = (1<<31);
	__asm__ volatile("mcr	p15, 0, %0, c9, c12, 1" :: "r" (en));
#endif
}</span>

用一些arm的汇编完成的动作，具体干啥后续再看
第三个函数

void platform_early_init(void)
{
	board_init();
	platform_clock_init();
	qgic_init();
	qtimer_init();
	scm_init();
}

子函数一

void board_init()
{
	platform_detect();
	target_detect(&board);   //这个是空函数
	target_baseband_detect(&board);  //根据之前的board的platform类型来选择board->baseband是那个地址
}

子函数11通过获取指定地址的信息来判断这块板子是什么类型的，并赋值给board这个结构体

static void platform_detect()
{
	struct smem_board_info_v6 board_info_v6;
	struct smem_board_info_v7 board_info_v7;
	struct smem_board_info_v8 board_info_v8;
	unsigned int board_info_len = 0;
	unsigned ret = 0;
	unsigned format = 0;
	unsigned pmic_type = 0;
	uint8_t i;
	uint16_t format_major = 0;
	uint16_t format_minor = 0;

	ret = smem_read_alloc_entry_offset(SMEM_BOARD_INFO_LOCATION,
						   &format, sizeof(format), 0);
	if (ret)
		return;

	/* Extract the major & minor version info,
	 * Upper two bytes: major info
	 * Lower two byets: minor info
	 */
	format_major = (format & 0xffff0000) >> 16;
	format_minor = format & 0x0000ffff;

	if (format_major == 0x0)
	{
		if (format_minor == 6)
		{
			board_info_len = sizeof(board_info_v6);

			ret = smem_read_alloc_entry(SMEM_BOARD_INFO_LOCATION,
					&board_info_v6,
					board_info_len);
			if (ret)
				return;

			board.platform = board_info_v6.board_info_v3.msm_id;
			board.platform_version = board_info_v6.board_info_v3.msm_version;
			board.platform_hw = board_info_v6.board_info_v3.hw_platform;
			board.platform_subtype = board_info_v6.platform_subtype;
		}
		else if (format_minor == 7)
		{
			board_info_len = sizeof(board_info_v7);

			ret = smem_read_alloc_entry(SMEM_BOARD_INFO_LOCATION,
					&board_info_v7,
					board_info_len);
			if (ret)
				return;

			board.platform = board_info_v7.board_info_v3.msm_id;
			board.platform_version = board_info_v7.board_info_v3.msm_version;
			board.platform_hw = board_info_v7.board_info_v3.hw_platform;
			board.platform_subtype = board_info_v7.platform_subtype;
			board.pmic_info[0].pmic_type = board_info_v7.pmic_type;
			board.pmic_info[0].pmic_version = board_info_v7.pmic_version;
		}
		else if (format_minor >= 8)
		{
			dprintf(INFO, "Minor socinfo format detected: %u.%u\n", format_major, format_minor);

			board_info_len = sizeof(board_info_v8);

			ret = smem_read_alloc_entry(SMEM_BOARD_INFO_LOCATION,
					&board_info_v8,
					board_info_len);
			if (ret)
				return;

			board.platform = board_info_v8.board_info_v3.msm_id;
			board.platform_version = board_info_v8.board_info_v3.msm_version;
			board.platform_hw = board_info_v8.board_info_v3.hw_platform;
			board.platform_subtype = board_info_v8.platform_subtype;

			/*
			 * fill in board.target with variant_id information
			 * bit no         |31  24 | 23   16            | 15   8             |7         0|
			 * board.target = |subtype| plat_hw_ver major  | plat_hw_ver minor  |hw_platform|
			 *
			 */
			board.target = (((board_info_v8.platform_subtype & 0xff) << 24) |
						   (((board_info_v8.platform_version >> 16) & 0xff) << 16) |
						   ((board_info_v8.platform_version & 0xff) << 8) |
						   (board_info_v8.board_info_v3.hw_platform & 0xff));

			for (i = 0; i < SMEM_V8_SMEM_MAX_PMIC_DEVICES; i++) {
				board.pmic_info[i].pmic_type = board_info_v8.pmic_info[i].pmic_type;
				board.pmic_info[i].pmic_version = board_info_v8.pmic_info[i].pmic_version;

				/*
				 * fill in pimc_board_info with pmic type and pmic version information
				 * bit no  		  	    |31  24   | 23  16 	    | 15   8 	     |7		  0|
				 * pimc_board_info = |Unused | Major version | Minor version|PMIC_MODEL|
				 *
				 */
				pmic_type = board_info_v8.pmic_info[i].pmic_type == PMIC_IS_INVALID? 0 : board_info_v8.pmic_info[i].pmic_type;

				board.pmic_info[i].pmic_target = (((board_info_v8.pmic_info[i].pmic_version >> 16) & 0xff) << 16) |
					   ((board_info_v8.pmic_info[i].pmic_version & 0xff) << 8) | (pmic_type & 0xff);
			}

			if (format_minor == 0x9)
				board.foundry_id = board_info_v8.foundry_id;
		}

		/* HLOS subtype
		 * bit no                        |31    20 | 19        16|15    13 |12      11 | 10          8 | 7     0|
		 * board.platform_hlos_subtype = |reserved | Boot device |Reserved | Panel     | DDR detection | subtype|
		 *                               |  bits   |             |  bits   | Detection |
		 */
		board.platform_hlos_subtype = (board_get_ddr_subtype() << 8) | (platform_get_boot_dev() << 16) | (platform_detect_panel() << 11);
	}
	else
	{
		dprintf(CRITICAL, "Unsupported board info format %u.%u\n", format_major, format_minor);
		ASSERT(0);
	}
}

主要的特点是对地址的强制转型

比如

smem = (struct smem *)smem_addr;