【精读Uboot】SPL阶段的board_init_r详细分析

对于i.MX平台上的SPL来说,其不会直接跳转到Uboot,而是在SPL阶段借助BOOTROM跳转到ATF,然后再通过ATF跳转到Uboot。

board_init_f会初始化设备相关的硬件,最后进入board_init_r为镜像跳转做准备。下面是board_init_r调用的核心函数流程,接下来我们会对其中的函数进行详细分析。

spl_board_init //board/freescale/imx93_evk/spl.c
board_boot_order(spl_boot_list)//spl_boot_device获取SPL启动设备 arch/arm/mach-imx/imx8/cpu.c
spl_boot_device//arch/arm/mach-imx/spl.c
    ->spl_board_boot_device//board/freescale/imx93_evk/spl.c
spl_return_to_bootrom
board_return_to_bootrom//arch/arm/mach-imx/spl_imx_romapi.c

1、spl_board_init

对于i.MX93芯片来说,spl_board_init启动ELE了引擎。这里不对ELE进行详细分析。

//board/freescale/imx93_evk/spl.c
void spl_board_init(void)
{
	int ret;

	puts("Normal Boot\n");

	ret = ahab_start_rng();
	if (ret)
		printf("Fail to start RNG: %d\n", ret);
}

2、board_boot_order

spl_boot_device根据boot配置获取当前的启动设备。对于使用SCU的芯片需要特殊处理BOOT_DEVICE_SPI类型的设备。

//arch/arm/mach-imx/imx8/cpu.c,适用于93
void board_boot_order(u32 *spl_boot_list)
{
	spl_boot_list[0] = spl_boot_device();

	if (spl_boot_list[0] == BOOT_DEVICE_SPI) {
		/* Check whether we own the flexspi0, if not, use NOR boot */
		if (!sc_rm_is_resource_owned(-1, SC_R_FSPI_0))
			spl_boot_list[0] = BOOT_DEVICE_NOR;
	}
}

spl_board_boot_device函数内容可以看出,i.MX8以及i.MX9系列芯片的SPL跳转皆是由BOOTROM辅助实现的,因为这里直接返回了BOOT_DEVICE_BOOTROM

//arch/arm/mach-imx/spl.c
u32 spl_boot_device(void)
{
	enum boot_device boot_device_spl = get_boot_device();
	return spl_board_boot_device(boot_device_spl);
}

int spl_board_boot_device(enum boot_device boot_dev_spl)
{
#ifdef CONFIG_SPL_BOOTROM_SUPPORT
	return BOOT_DEVICE_BOOTROM;
#else
	switch (boot_dev_spl) {
	case SD1_BOOT:
	case MMC1_BOOT:
		return BOOT_DEVICE_MMC1;
	case SD2_BOOT:
	case MMC2_BOOT:
		return BOOT_DEVICE_MMC2;
	default:
		return BOOT_DEVICE_NONE;
	}
#endif
}

3、spl_return_to_bootrom

由于上面返回的boot设备是BOOT_DEVICE_BOOTROM,因此这里各家定义的board_return_to_bootrom用于辅助跳转。

通过ROM API查询当前的启动设备和启动阶段,启动阶段可以分为Primary bootSecondary bootRecovery bootUSB boot,打印对应的启动阶段信息,最后使用ROM API将Uboot搬运到DDR的对应位置。

int board_return_to_bootrom(struct spl_image_info *spl_image,
			    struct spl_boot_device *bootdev)
{
	volatile gd_t *pgd = gd;
	int ret;
	u32 boot, bstage;

	ret = g_rom_api->query_boot_infor(QUERY_BT_DEV, &boot,
					  ((uintptr_t)&boot) ^ QUERY_BT_DEV);
	ret |= g_rom_api->query_boot_infor(QUERY_BT_STAGE, &bstage,
					   ((uintptr_t)&bstage) ^ QUERY_BT_STAGE);
	set_gd(pgd);

	if (ret != ROM_API_OKAY) {
		puts("ROMAPI: failure at query_boot_info\n");
		return -1;
	}

	printf("Boot Stage: ");

	switch (bstage) {
	case BT_STAGE_PRIMARY:
		printf("Primary boot\n");
		break;
	case BT_STAGE_SECONDARY:
		printf("Secondary boot\n");
		break;
	case BT_STAGE_RECOVERY:
		printf("Recovery boot\n");
		break;
	case BT_STAGE_USB:
		printf("USB boot\n");
		break;
	default:
		printf("Unknow (0x%x)\n", bstage);
	}
	//USB下载模式
	if (is_boot_from_stream_device(boot))
		return spl_romapi_load_image_stream(spl_image, bootdev);

	return spl_romapi_load_image_seekable(spl_image, bootdev, boot);
}

4、spl_romapi_load_image_seekable

下面我们将分析ROM API是如何将Uboot搬运到指定位置的。

  1. 通过query_boot_infor查询IVT的偏移量、pagesize和image_offset。

  2. 获取header的位置

    header = (struct image_header *)(CONFIG_SPL_IMX_ROMAPI_LOADADDR);//0x48000000 内存地址
    
  3. 获取Uboot在MMC介质中的偏移量,将其存储在offset(0x41400)中。

    offset = spl_romapi_get_uboot_base(image_offset, rom_bt_dev);
    
    ulong spl_romapi_get_uboot_base(u32 image_offset, u32 rom_bt_dev)
    {
    	ulong end;
    
    	image_offset = spl_arch_boot_image_offset(image_offset, rom_bt_dev);
    
    	end = get_imageset_end((void *)(ulong)image_offset, ROM_API_DEV);
    	end = ROUND(end, SZ_1K);
    
    	printf("Load image from 0x%lx by ROM_API\n", end);
    
    	return end;
    }
    
  4. 使用download_image函数从MMC中的0x41400处下载header信息到DDR中的0x48000000处,后续需要对header里的信息进行判断(image_get_magic(header) == FDT_MAGIC)。这个header由mkimage_imx8.c写入。

    g_rom_api->download_image((u8 *)header, offset, size,
    					((uintptr_t)header) ^ offset ^ size);
    
  5. 设置其他固件的信息,对于93/8ulp来说调用的是spl_load_imx_container函数,其余芯片为spl_load_simple_fit函数。spl_load_simple_fit这个函数会解析itb文件,获取里面的配置信息,填充spl_image_infospl_load_info中的信息,加载ATF做好跳转之前的准备。

5、spl_load_simple_fit

在进入之前,设置了load.readspl_romapi_read_seekable,然后spl_simple_fit_read会调用传入的read函数和上一节而最后读取到内存的header读取整个fit固件。这个是后续读取固件的核心函数。

if (IS_ENABLED(CONFIG_SPL_LOAD_FIT) && image_get_magic(header) == FDT_MAGIC) {
		struct spl_load_info load;

		memset(&load, 0, sizeof(load));
		load.bl_len = pagesize;
		load.read = spl_romapi_read_seekable;
		load.priv = &pagesize;
		return spl_load_simple_fit(spl_image, &load, offset / pagesize, header);
}

spl_load_simple_fit_fix_load使用ROM API读取itb到内存中,然后解析/configurations节点,其中的default配置名称和images的偏移量。

5.1、解析uboot

解析默认config(config-1)下面的firmware所指向的名称,这里解析出"uboot-1",然后返回出这个uboot节点在itb文件中的偏移量。一个config只有一个firmware,可以是uboot也可以是kernel,其余均为external数据。

spl_load_fit_image根据解析出的加载地址,将u-boot-nodtb.bin放到加载地址处。然后填充spl_image_info中的load_addr等信息。

#define FIT_FIRMWARE_PROP	"firmware"
node = spl_fit_get_image_node(&ctx, FIT_FIRMWARE_PROP, 0);

ret = spl_load_fit_image(info, sector, &ctx, node, spl_image);

5.2、解析fdt

spl_fit_append_fdt首先也是解析出its中关于设备树的相关信息,然后使用fdt_overlay_apply_verbose->fdt_overlay_apply将its中需要overlay的部分覆盖进原始dtb中。

if (os_takes_devicetree(spl_image->os)) {
		ret = spl_fit_append_fdt(spl_image, info, sector, &ctx);
}

overlay dtb格式1:

/dts-v1/;
/plugin/;

 / {
        fragment@0 {
            target-path = "/";
            __overlay__ {
                /*在此添加要插入的节点*/
                .......
            };
        };

        fragment@1 {
            target = <&XXXXX>;
            __overlay__ {
                /*在此添加要插入的节点*/
                .......
            };
        };
    .......
 };

overlay dtb格式2:

/dts-v1/;
/plugin/;

&{/} {
    /*此处在根节点"/"下,添加要插入的节点或者属性*/
};

&XXXXX {
    /*此处在节点"XXXXX"下,添加要插入的节点或者属性*/
};

5.3、解析loadables

和解析加载uboot类似,先找到its节点中的信息,然后根据这些信息将atf和tee放到指定位置。

for (; ; index++) {
		uint8_t os_type = IH_OS_INVALID;

		node = spl_fit_get_image_node(&ctx, "loadables", index);

		image_info.load_addr = 0;
		ret = spl_load_fit_image(info, sector, &ctx, node, &image_info);

		/* Record our loadables into the FDT */
		if (spl_image->fdt_addr)
			spl_fit_record_loadable(&ctx, index,
						spl_image->fdt_addr,
						&image_info);
	}

如果firmware属性中未定义entry值,那么将第一个loadables的entry作为跳转入口(spl_image->entry_point)。从its中我们可以知道,第一个loadables就是atf。

6、跳转至ATF

直接跳转进spl_image->entry_point所定义的地址,也就是进入ATF中。

arch/arm/mach-imx/spl.c
/*
 * +------------+  0x0 (DDR_UIMAGE_START) -
 * |   Header   |                          |
 * +------------+  0x40                    |
 * |            |                          |
 * |            |                          |
 * |            |                          |
 * |            |                          |
 * | Image Data |                          |
 * .            |                          |
 * .            |                           > Stuff to be authenticated ----+
 * .            |                          |                                |
 * |            |                          |                                |
 * |            |                          |                                |
 * +------------+                          |                                |
 * |            |                          |                                |
 * | Fill Data  |                          |                                |
 * |            |                          |                                |
 * +------------+ Align to ALIGN_SIZE      |                                |
 * |    IVT     |                          |                                |
 * +------------+ + IVT_SIZE              -                                 |
 * |            |                                                           |
 * |  CSF DATA  | <---------------------------------------------------------+
 * |            |
 * +------------+
 * |            |
 * | Fill Data  |
 * |            |
 * +------------+ + CSF_PAD_SIZE
 */

__weak void __noreturn jump_to_image_no_args(struct spl_image_info *spl_image)
{
	typedef void __noreturn (*image_entry_noargs_t)(void);
	uint32_t offset;

	image_entry_noargs_t image_entry =
		(image_entry_noargs_t)(unsigned long)spl_image->entry_point;

	debug("image entry point: 0x%lX\n", spl_image->entry_point);

	if (spl_image->flags & SPL_FIT_FOUND) {
		image_entry();
	} else {
		/*
		 * HAB looks for the CSF at the end of the authenticated
		 * data therefore, we need to subtract the size of the
		 * CSF from the actual filesize
		 */
		offset = spl_image->size - CONFIG_CSF_SIZE;
		if (!imx_hab_authenticate_image(spl_image->load_addr,
						offset + IVT_SIZE +
						CSF_PAD_SIZE, offset)) {
			image_entry();
		} else {
			panic("spl: ERROR:  image authentication fail\n");
		}
	}
}

附录1:its表

/dts-v1/;

/ {
	description = "Configuration to load ATF before U-Boot";
	#address-cells = <1>;

	images {
		uboot-1 {
			description = "U-Boot (64-bit)";
			data = /incbin/("u-boot-nodtb.bin");
			type = "standalone";
			arch = "arm64";
			compression = "none";
			load = <0x40200000>;
		};
		fdt-1 {
			description = "evk";
			data = /incbin/("evk.dtb");
			type = "flat_dt";
			compression = "none";
		};
		atf-1 {
			description = "ARM Trusted Firmware";
			data = /incbin/("bl31.bin");
			type = "firmware";
			arch = "arm64";
			compression = "none";
			load = <0x00970000>;
			entry = <0x00970000>;
		};
		tee-1 {
			description = "TEE firmware";
			data = /incbin/("tee.bin");
			type = "firmware";
			arch = "arm64";
			compression = "none";
			load = <0x56000000>;
			entry = <0x56000000>;
		};
	};
	configurations {
		default = "config-1";

		config-1 {
			description = "evk";
			firmware = "uboot-1";
			loadables = "atf-1", "tee-1";
			fdt = "fdt-1";
		};
	};
};

附录2:启动log

i.MX93

U-Boot SPL 2022.04-lf_v2022.04+g1734965341 (Jun 30 2023 - 10:23:49 +0000)
SOC: 0xa0009300
LC: 0x40010
M33 prepare ok
>>SPL: board_init_r()
spl_init
Normal Boot
Trying to boot from BOOTROM
Boot Stage: Primary boot
image offset 0x0, pagesize 0x200, ivt offset 0x0 
Load image from 0x41400 by ROM_API 
Unsupported OS image.. Jumping nevertheless..
image entry point: 0x204e0000

i.MX8MP

U-Boot SPL 2023.04-lf_v2023.04+gaf7d004eaf (Aug 14 2023 - 03:48:45 +0000)
DDRINFO: start DRAM init
DDRINFO: DRAM rate 4000MTS
DDRINFO:ddrphy calibration done
DDRINFO: ddrmix config done
>>SPL: board_init_r()
spl_init
SEC0:  RNG instantiated
Normal Boot
Trying to boot from BOOTROM
Boot Stage: Primary boot
image offset 0x0, pagesize 0x200, ivt offset 0x0
Jumping to U-Boot...
image entry point: 0x970000

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