diff mbox series

[U-Boot,v2,5/7] armv8: layerscape: Eanble falcon boot

Message ID 1505415699-3401-6-git-send-email-york.sun@nxp.com
State Superseded
Delegated to: York Sun
Headers show
Series Enable falcon boot for LS1043ARDB | expand

Commit Message

York Sun Sept. 14, 2017, 7:01 p.m. UTC
Add jump_to_image_linux() for arm64. Add "noreturn" flag to
armv8_switch_to_el2(). Add hooks to fsl-layerscape to enable falcon
boot.

Signed-off-by: York Sun <york.sun@nxp.com>

---

Changes in v2:
Relace getenv_f() with env_get_f() after rebasing to latet master.

 .../arm/cpu/armv8/fsl-layerscape/doc/README.falcon | 140 +++++++++++++++++++++
 arch/arm/cpu/armv8/fsl-layerscape/spl.c            |  29 +++++
 arch/arm/include/asm/system.h                      |   2 +-
 arch/arm/lib/spl.c                                 |  11 ++
 4 files changed, 181 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon

Comments

Simon Glass Sept. 17, 2017, 5:54 p.m. UTC | #1
+Philippe for review

On 14 September 2017 at 13:01, York Sun <york.sun@nxp.com> wrote:
> Add jump_to_image_linux() for arm64. Add "noreturn" flag to
> armv8_switch_to_el2(). Add hooks to fsl-layerscape to enable falcon
> boot.
>
> Signed-off-by: York Sun <york.sun@nxp.com>
>
> ---
>
> Changes in v2:
> Relace getenv_f() with env_get_f() after rebasing to latet master.
>
>  .../arm/cpu/armv8/fsl-layerscape/doc/README.falcon | 140 +++++++++++++++++++++
>  arch/arm/cpu/armv8/fsl-layerscape/spl.c            |  29 +++++
>  arch/arm/include/asm/system.h                      |   2 +-
>  arch/arm/lib/spl.c                                 |  11 ++
>  4 files changed, 181 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon

Reviewed-by: Simon Glass <sjg@chromium.org>
Lukasz Majewski Sept. 25, 2017, 2:17 p.m. UTC | #2
Hi York,

If you don't mind, I would like to ask you for some help and 
clarification regarding your work.

> Add jump_to_image_linux() for arm64. Add "noreturn" flag to
> armv8_switch_to_el2(). Add hooks to fsl-layerscape to enable falcon
> boot.

I'm trying to do the same on imx6q board (armv7).

> 
> Signed-off-by: York Sun <york.sun@nxp.com>
> 
> ---
> 
> Changes in v2:
> Relace getenv_f() with env_get_f() after rebasing to latet master.
> 
>   .../arm/cpu/armv8/fsl-layerscape/doc/README.falcon | 140 +++++++++++++++++++++
>   arch/arm/cpu/armv8/fsl-layerscape/spl.c            |  29 +++++
>   arch/arm/include/asm/system.h                      |   2 +-
>   arch/arm/lib/spl.c                                 |  11 ++
>   4 files changed, 181 insertions(+), 1 deletion(-)
>   create mode 100644 arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon
> 
> diff --git a/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon b/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon
> new file mode 100644
> index 0000000..282b19f
> --- /dev/null
> +++ b/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon
> @@ -0,0 +1,140 @@
> +Falcon boot option
> +------------------
> +Falcon boot is a short cut boot method for SD/eMMC targets. It skips loading the
> +RAM version U-Boot. Instead, it loads FIT image and boot directly to Linux.
> +CONFIG_SPL_OS_BOOT enables falcon boot. CONFIG_SPL_LOAD_FIT enables the FIT
					   ^^^^^^ - this is a bit cumbersome, since it requires some stub 
for dtb creation (but this can be fixed for boards not yet supporting 
dts u-boot configuration).

> +image support (also need CONFIG_SPL_OF_LIBFDT, CONFIG_SPL_FIT and optionally
> +CONFIG_SPL_GZIP).
> +
> +To enable falcon boot, a hook function spl_start_uboot() returns 0 to indicate
> +booting U-Boot is not the first choice. The kernel FIT image needs to be put
> +at CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR. SPL mmc driver reads the header to
> +determine if this is a FIT image. If true, FIT image components are parsed and
> +copied or decompressed (if applicable) to their desitinations. If FIT image is
> +not found, normal U-Boot flow will follow.

This part is similar to the one for old, venerable uImage.

> +
> +An important part of falcon boot is to prepare the device tree. A normal U-Boot
> +does FDT fixups when booting Linux. For falcon boot, Linux boots directly from
> +SPL, skipping the normal U-Boot. The device tree has to be prepared in advance.
> +A command "spl export" should be called under the normal RAM version U-Boot.
> +It is equivalent to go through "bootm" step-by-step until device tree fixup is
> +done. The device tree in memory is the one needed for falcon boot. Falcon boot
> +flow suggests to save this image to SD/eMMC at the location pointed by macro
> +CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR, with maximum size specified by macro
> +CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS. However, when FIT image is used for
> +Linux, the device tree stored in FIT image overwrites the memory loaded by spl
> +driver from these sectors. We could change this loading order to favor the
> +stored sectors. But when secure boot is enabled, these sectors are used for
> +signature header and needs to be loaded before the FIT image. So it is important
> +to understand the device tree in FIT image should be the one actually used, or
> +leave it abscent to favor the stored sectors. It is easier to deploy the FIT
> +image with embedded static device tree to multiple boards.
> +
> +Macro CONFIG_SYS_SPL_ARGS_ADDR serves two purposes. One is the pointer to load
> +the stored sectors to. Normally this is the static device tree. The second
> +purpose is the memory location of signature header for secure boot. After the
> +FIT image is loaded into memory, it is validated against the signature header
> +before individual components are extracted (and optionally decompressed) into
> +their final memory locations, respectivelly. After the validation, the header
> +is no longer used. The static device tree is copied into this location. So
> +this macro is passed as the location of device tree when booting Linux.

I've not yet go to this point -> Please look into below comments.

I'm just curious - how can I specify the DTBs precedence? I mean how to 
decide if one from FIT or from eMMC sector are used?


> +components. Otherwise U-Boot cannot load them correctly.
> +
> +Generate FIT image with static device tree
> +------------------------------------------
> +Example:
> +
> +/dts-v1/;

I'm trying to load fitImage (with kernel + 2 dtbs) from eMMC directly by 
SPL. The fitImage has been generated with OE-core recipe. The same 
results are with one generated with mkimage.

> +
> +/ {
> +	description = "Image file for the LS1043A Linux Kernel";
> +	#address-cells = <1>;
> +
> +	images {
> +		kernel@1 {
> +			description = "ARM64 Linux kernel";
> +			data = /incbin/("./arch/arm64/boot/Image.gz");
> +			type = "kernel";
> +			arch = "arm64";
> +			os = "linux";
> +			compression = "gzip";
> +			load = <0x80080000>;
> +			entry = <0x80080000>;

			^^^^ common/spl/spl_fit.c - function spl_load_fit_image()
			requires "data-offset" and "data-size" properties to be defined - 
otherwise we exit with -ENOENT.

Even when creating my fitImage with u-boot's mkimage those properties 
haven't been added.


> +		};
> +		fdt@1 {
> +			description = "Flattened Device Tree blob";
> +			data = /incbin/("./fsl-ls1043ardb-static.dtb");
> +			type = "flat_dt";
> +			arch = "arm64";
> +			compression = "none";
> +			load = <0x90000000>;
> +		};
> +		ramdisk@1 {
> +			description = "LS1043 Ramdisk";
> +                        data = /incbin/("./rootfs.cpio.gz");
> +			type = "ramdisk";
> +			arch = "arm64";
> +			os = "linux";
> +			compression = "gzip";
> +			load = <0xa0000000>;
> +		};
> +	};
> +
> +	configurations {
> +		default = "config@1";
> +		config@1 {
> +			description = "Boot Linux kernel";
> +			kernel = "kernel@1";
> +			fdt = "fdt@1";
> +			ramdisk = "ramdisk@1";
> +			loadables = "fdt", "ramdisk";

			^^^
			Isn't here loadables require "kernel", "fdt", "ramdisk" ?

Could you share how have you managed to load fitImage from SPL? Maybe 
I'm missing some patches? Is there any "reference" repo, so I could see 
the "complete" work?


> +		};
> +	};
> +};
> +
> +The "loadables" is not optional. It tells SPL which images to load into memory.
> +
> +Other things to consider
> +-----------------------
> +Falcon boot skips a lot of initialization in U-Boot. If Linux expects the
> +hardware to be initialized by U-Boot, the related code should be ported to SPL
> +build. For example, if Linux expect Ethernet PHY to be initialized in U-Boot
> +(which is not a common case), the PHY initialization has to be included in
> +falcon boot. This increases the SPL image size and should be handled carefully.
> +If Linux has PHY driver enabled, it still depends on the correct MDIO bus setup
> +in U-Boot. Normal U-Boot sets the MDC ratio to generate a proper clock signal.
> diff --git a/arch/arm/cpu/armv8/fsl-layerscape/spl.c b/arch/arm/cpu/armv8/fsl-layerscape/spl.c
> index 2776240..30b5432 100644
> --- a/arch/arm/cpu/armv8/fsl-layerscape/spl.c
> +++ b/arch/arm/cpu/armv8/fsl-layerscape/spl.c
> @@ -116,4 +116,33 @@ void board_init_f(ulong dummy)
>   	gd->arch.tlb_allocated = gd->arch.tlb_addr;
>   #endif	/* CONFIG_SPL_FSL_LS_PPA */
>   }
> +
> +#ifdef CONFIG_SPL_OS_BOOT
> +/*
> + * Return
> + * 0 if booting into OS is selected
> + * 1 if booting into U-Boot is selected
> + */
> +int spl_start_uboot(void)
> +{
> +	char s[8];
> +
> +	env_init();
> +	env_get_f("boot_os", s, sizeof(s));
> +	if ((s != NULL) && (*s != '0' && *s != 'n' && *s != 'N' &&
> +			    *s != 'f' && *s != 'F'))
> +		return 0;
> +
> +	return 1;
> +}
> +#endif	/* CONFIG_SPL_OS_BOOT */
> +#ifdef CONFIG_SPL_LOAD_FIT
> +int board_fit_config_name_match(const char *name)
> +{
> +	/* Just empty function now - can't decide what to choose */
> +	debug("%s: %s\n", __func__, name);
> +
> +	return 0;
> +}
> +#endif
>   #endif /* CONFIG_SPL_BUILD */
> diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
> index 79bd19a..7d8dc44 100644
> --- a/arch/arm/include/asm/system.h
> +++ b/arch/arm/include/asm/system.h
> @@ -215,7 +215,7 @@ void __asm_switch_ttbr(u64 new_ttbr);
>    * @entry_point: kernel entry point
>    * @es_flag:     execution state flag, ES_TO_AARCH64 or ES_TO_AARCH32
>    */
> -void armv8_switch_to_el2(u64 args, u64 mach_nr, u64 fdt_addr,
> +void __noreturn armv8_switch_to_el2(u64 args, u64 mach_nr, u64 fdt_addr,
>   			 u64 arg4, u64 entry_point, u64 es_flag);
>   /*
>    * Switch from EL2 to EL1 for ARMv8
> diff --git a/arch/arm/lib/spl.c b/arch/arm/lib/spl.c
> index 27d6682..ab5d227 100644
> --- a/arch/arm/lib/spl.c
> +++ b/arch/arm/lib/spl.c
> @@ -7,6 +7,7 @@
>    *
>    * SPDX-License-Identifier:	GPL-2.0+
>    */
> +
>   #include <common.h>
>   #include <config.h>
>   #include <spl.h>
> @@ -47,6 +48,15 @@ void __weak board_init_f(ulong dummy)
>    * image.
>    */
>   #ifdef CONFIG_SPL_OS_BOOT
> +#ifdef CONFIG_ARM64
> +void __noreturn jump_to_image_linux(struct spl_image_info *spl_image)
> +{
> +	debug("Entering kernel arg pointer: 0x%p\n", spl_image->arg);
> +	cleanup_before_linux();
> +	armv8_switch_to_el2((u64)spl_image->arg, 0, 0, 0,
> +			    spl_image->entry_point, ES_TO_AARCH64);
> +}
> +#else
>   void __noreturn jump_to_image_linux(struct spl_image_info *spl_image)
>   {
>   	unsigned long machid = 0xffffffff;
> @@ -62,4 +72,5 @@ void __noreturn jump_to_image_linux(struct spl_image_info *spl_image)
>   	cleanup_before_linux();
>   	image_entry(0, machid, spl_image->arg);
>   }
> +#endif	/* CONFIG_ARM64 */
>   #endif
>
Marek Vasut Sept. 25, 2017, 2:25 p.m. UTC | #3
On 09/25/2017 04:17 PM, Łukasz Majewski wrote:

Nit -- Eanble in subject .
        ^^.... Enable

Best regards,
Marek Vasut
York Sun Sept. 25, 2017, 5:08 p.m. UTC | #4
On 09/25/2017 07:17 AM, Łukasz Majewski wrote:
> Hi York,
> 
> If you don't mind, I would like to ask you for some help and
> clarification regarding your work.
> 
>> Add jump_to_image_linux() for arm64. Add "noreturn" flag to
>> armv8_switch_to_el2(). Add hooks to fsl-layerscape to enable falcon
>> boot.
> 
> I'm trying to do the same on imx6q board (armv7).
> 
>>
>> Signed-off-by: York Sun <york.sun@nxp.com>
>>
>> ---
>>
>> Changes in v2:
>> Relace getenv_f() with env_get_f() after rebasing to latet master.
>>
>>    .../arm/cpu/armv8/fsl-layerscape/doc/README.falcon | 140 +++++++++++++++++++++
>>    arch/arm/cpu/armv8/fsl-layerscape/spl.c            |  29 +++++
>>    arch/arm/include/asm/system.h                      |   2 +-
>>    arch/arm/lib/spl.c                                 |  11 ++
>>    4 files changed, 181 insertions(+), 1 deletion(-)
>>    create mode 100644 arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon
>>
>> diff --git a/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon b/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon
>> new file mode 100644
>> index 0000000..282b19f
>> --- /dev/null
>> +++ b/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon
>> @@ -0,0 +1,140 @@
>> +Falcon boot option
>> +------------------
>> +Falcon boot is a short cut boot method for SD/eMMC targets. It skips loading the
>> +RAM version U-Boot. Instead, it loads FIT image and boot directly to Linux.
>> +CONFIG_SPL_OS_BOOT enables falcon boot. CONFIG_SPL_LOAD_FIT enables the FIT
> 					   ^^^^^^ - this is a bit cumbersome, since it requires some stub
> for dtb creation (but this can be fixed for boards not yet supporting
> dts u-boot configuration).
> 
>> +image support (also need CONFIG_SPL_OF_LIBFDT, CONFIG_SPL_FIT and optionally
>> +CONFIG_SPL_GZIP).
>> +
>> +To enable falcon boot, a hook function spl_start_uboot() returns 0 to indicate
>> +booting U-Boot is not the first choice. The kernel FIT image needs to be put
>> +at CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR. SPL mmc driver reads the header to
>> +determine if this is a FIT image. If true, FIT image components are parsed and
>> +copied or decompressed (if applicable) to their desitinations. If FIT image is
>> +not found, normal U-Boot flow will follow.
> 
> This part is similar to the one for old, venerable uImage.
> 
>> +
>> +An important part of falcon boot is to prepare the device tree. A normal U-Boot
>> +does FDT fixups when booting Linux. For falcon boot, Linux boots directly from
>> +SPL, skipping the normal U-Boot. The device tree has to be prepared in advance.
>> +A command "spl export" should be called under the normal RAM version U-Boot.
>> +It is equivalent to go through "bootm" step-by-step until device tree fixup is
>> +done. The device tree in memory is the one needed for falcon boot. Falcon boot
>> +flow suggests to save this image to SD/eMMC at the location pointed by macro
>> +CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR, with maximum size specified by macro
>> +CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS. However, when FIT image is used for
>> +Linux, the device tree stored in FIT image overwrites the memory loaded by spl
>> +driver from these sectors. We could change this loading order to favor the
>> +stored sectors. But when secure boot is enabled, these sectors are used for
>> +signature header and needs to be loaded before the FIT image. So it is important
>> +to understand the device tree in FIT image should be the one actually used, or
>> +leave it abscent to favor the stored sectors. It is easier to deploy the FIT
>> +image with embedded static device tree to multiple boards.
>> +
>> +Macro CONFIG_SYS_SPL_ARGS_ADDR serves two purposes. One is the pointer to load
>> +the stored sectors to. Normally this is the static device tree. The second
>> +purpose is the memory location of signature header for secure boot. After the
>> +FIT image is loaded into memory, it is validated against the signature header
>> +before individual components are extracted (and optionally decompressed) into
>> +their final memory locations, respectivelly. After the validation, the header
>> +is no longer used. The static device tree is copied into this location. So
>> +this macro is passed as the location of device tree when booting Linux.
> 
> I've not yet go to this point -> Please look into below comments.
> 
> I'm just curious - how can I specify the DTBs precedence? I mean how to
> decide if one from FIT or from eMMC sector are used?

By the order of loading ARGS first, then FIT. If you have static device 
tree in FIT image, it can overwrite the image loaded from ARGS. For my 
testing, I have verified FIT image without device tree in which case the 
device tree is loaded from ARGS.

> 
> 
>> +components. Otherwise U-Boot cannot load them correctly.
>> +
>> +Generate FIT image with static device tree
>> +------------------------------------------
>> +Example:
>> +
>> +/dts-v1/;
> 
> I'm trying to load fitImage (with kernel + 2 dtbs) from eMMC directly by
> SPL. The fitImage has been generated with OE-core recipe. The same
> results are with one generated with mkimage.
> 
>> +
>> +/ {
>> +	description = "Image file for the LS1043A Linux Kernel";
>> +	#address-cells = <1>;
>> +
>> +	images {
>> +		kernel@1 {
>> +			description = "ARM64 Linux kernel";
>> +			data = /incbin/("./arch/arm64/boot/Image.gz");
>> +			type = "kernel";
>> +			arch = "arm64";
>> +			os = "linux";
>> +			compression = "gzip";
>> +			load = <0x80080000>;
>> +			entry = <0x80080000>;
> 
> 			^^^^ common/spl/spl_fit.c - function spl_load_fit_image()
> 			requires "data-offset" and "data-size" properties to be defined -
> otherwise we exit with -ENOENT.

I thought we fixed that. In my previous patch set I added FIT support. 
The data-offset is used for external data (i.e. data is outside of FIT 
structure, eg. U-Boot). For Linux FIT image, the data is embedded. See 
spl_load_fit_image().

> 
> Even when creating my fitImage with u-boot's mkimage those properties
> haven't been added.

Because data-offset is not used for embedded data.

> 
> 
>> +		};
>> +		fdt@1 {
>> +			description = "Flattened Device Tree blob";
>> +			data = /incbin/("./fsl-ls1043ardb-static.dtb");
>> +			type = "flat_dt";
>> +			arch = "arm64";
>> +			compression = "none";
>> +			load = <0x90000000>;
>> +		};
>> +		ramdisk@1 {
>> +			description = "LS1043 Ramdisk";
>> +                        data = /incbin/("./rootfs.cpio.gz");
>> +			type = "ramdisk";
>> +			arch = "arm64";
>> +			os = "linux";
>> +			compression = "gzip";
>> +			load = <0xa0000000>;
>> +		};
>> +	};
>> +
>> +	configurations {
>> +		default = "config@1";
>> +		config@1 {
>> +			description = "Boot Linux kernel";
>> +			kernel = "kernel@1";
>> +			fdt = "fdt@1";
>> +			ramdisk = "ramdisk@1";
>> +			loadables = "fdt", "ramdisk";
> 
> 			^^^
> 			Isn't here loadables require "kernel", "fdt", "ramdisk" ?
> 
> Could you share how have you managed to load fitImage from SPL? Maybe
> I'm missing some patches? Is there any "reference" repo, so I could see
> the "complete" work?

I put the FIT image at CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR, see 
patch 7 in this series. With correct configuration, U-Boot SPL code 
looks for FIT image at this location. If not found, it continues to boot 
U-Boot RAM version as before. If found, falcon boot kicks in.

I have a temporary repo for debugging. See 
https://github.com/yorksun/u-boot/commits/test_patches. The code base 
has changed so this one will not be there for long.

York
diff mbox series

Patch

diff --git a/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon b/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon
new file mode 100644
index 0000000..282b19f
--- /dev/null
+++ b/arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon
@@ -0,0 +1,140 @@ 
+Falcon boot option
+------------------
+Falcon boot is a short cut boot method for SD/eMMC targets. It skips loading the
+RAM version U-Boot. Instead, it loads FIT image and boot directly to Linux.
+CONFIG_SPL_OS_BOOT enables falcon boot. CONFIG_SPL_LOAD_FIT enables the FIT
+image support (also need CONFIG_SPL_OF_LIBFDT, CONFIG_SPL_FIT and optionally
+CONFIG_SPL_GZIP).
+
+To enable falcon boot, a hook function spl_start_uboot() returns 0 to indicate
+booting U-Boot is not the first choice. The kernel FIT image needs to be put
+at CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR. SPL mmc driver reads the header to
+determine if this is a FIT image. If true, FIT image components are parsed and
+copied or decompressed (if applicable) to their desitinations. If FIT image is
+not found, normal U-Boot flow will follow.
+
+An important part of falcon boot is to prepare the device tree. A normal U-Boot
+does FDT fixups when booting Linux. For falcon boot, Linux boots directly from
+SPL, skipping the normal U-Boot. The device tree has to be prepared in advance.
+A command "spl export" should be called under the normal RAM version U-Boot.
+It is equivalent to go through "bootm" step-by-step until device tree fixup is
+done. The device tree in memory is the one needed for falcon boot. Falcon boot
+flow suggests to save this image to SD/eMMC at the location pointed by macro
+CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR, with maximum size specified by macro
+CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS. However, when FIT image is used for
+Linux, the device tree stored in FIT image overwrites the memory loaded by spl
+driver from these sectors. We could change this loading order to favor the
+stored sectors. But when secure boot is enabled, these sectors are used for
+signature header and needs to be loaded before the FIT image. So it is important
+to understand the device tree in FIT image should be the one actually used, or
+leave it abscent to favor the stored sectors. It is easier to deploy the FIT
+image with embedded static device tree to multiple boards.
+
+Macro CONFIG_SYS_SPL_ARGS_ADDR serves two purposes. One is the pointer to load
+the stored sectors to. Normally this is the static device tree. The second
+purpose is the memory location of signature header for secure boot. After the
+FIT image is loaded into memory, it is validated against the signature header
+before individual components are extracted (and optionally decompressed) into
+their final memory locations, respectivelly. After the validation, the header
+is no longer used. The static device tree is copied into this location. So
+this macro is passed as the location of device tree when booting Linux.
+
+Steps to prepare static device tree
+-----------------------------------
+To prepare the static device tree for Layerscape boards, it is important to
+understand the fixups in U-Boot. Memory size and location, as well as reserved
+memory blocks are added/updated. Ethernet MAC addressed are updated. FMan
+microcode (if used) is embedded in the device tree. Kernel command line and
+initrd information are embedded. Others including CPU status, boot method,
+Ethernet port status, etc. are also updated.
+
+Following normal booting process, all variables are set, all images are loaded
+before "bootm" command would be issued to boot, run command
+
+spl export fdt <address>
+
+where the address is the location of FIT image. U-Boot goes through the booting
+process as if "bootm start", "bootm loados", "bootm ramdisk"... commands but
+stops before "bootm go". There we have the fixed-up device tree in memory.
+We can check the device tree header by these commands
+
+fdt addr <fdt address>
+fdt header
+
+Where the fdt address is the device tree in memory. It is printed by U-Boot.
+It is useful to know the exact size. One way to extract this static device
+tree is to save it to eMMC/SD using command in U-Boot, and extract under Linux
+with these commands, repectivelly
+
+mmc write <address> <sector> <sectors>
+dd if=/dev/mmcblk0 of=<filename> bs=512 skip=<sector> count=<sectors>
+
+Note, U-Boot takes values as hexadecimals while Linux takes them as decimals by
+default. If using NAND or other storage, the commands are slightly different.
+When we have the static device tree image, we can re-make the FIT image with
+it. It is important to specify the load addresses in FIT image for every
+components. Otherwise U-Boot cannot load them correctly.
+
+Generate FIT image with static device tree
+------------------------------------------
+Example:
+
+/dts-v1/;
+
+/ {
+	description = "Image file for the LS1043A Linux Kernel";
+	#address-cells = <1>;
+
+	images {
+		kernel@1 {
+			description = "ARM64 Linux kernel";
+			data = /incbin/("./arch/arm64/boot/Image.gz");
+			type = "kernel";
+			arch = "arm64";
+			os = "linux";
+			compression = "gzip";
+			load = <0x80080000>;
+			entry = <0x80080000>;
+		};
+		fdt@1 {
+			description = "Flattened Device Tree blob";
+			data = /incbin/("./fsl-ls1043ardb-static.dtb");
+			type = "flat_dt";
+			arch = "arm64";
+			compression = "none";
+			load = <0x90000000>;
+		};
+		ramdisk@1 {
+			description = "LS1043 Ramdisk";
+                        data = /incbin/("./rootfs.cpio.gz");
+			type = "ramdisk";
+			arch = "arm64";
+			os = "linux";
+			compression = "gzip";
+			load = <0xa0000000>;
+		};
+	};
+
+	configurations {
+		default = "config@1";
+		config@1 {
+			description = "Boot Linux kernel";
+			kernel = "kernel@1";
+			fdt = "fdt@1";
+			ramdisk = "ramdisk@1";
+			loadables = "fdt", "ramdisk";
+		};
+	};
+};
+
+The "loadables" is not optional. It tells SPL which images to load into memory.
+
+Other things to consider
+-----------------------
+Falcon boot skips a lot of initialization in U-Boot. If Linux expects the
+hardware to be initialized by U-Boot, the related code should be ported to SPL
+build. For example, if Linux expect Ethernet PHY to be initialized in U-Boot
+(which is not a common case), the PHY initialization has to be included in
+falcon boot. This increases the SPL image size and should be handled carefully.
+If Linux has PHY driver enabled, it still depends on the correct MDIO bus setup
+in U-Boot. Normal U-Boot sets the MDC ratio to generate a proper clock signal.
diff --git a/arch/arm/cpu/armv8/fsl-layerscape/spl.c b/arch/arm/cpu/armv8/fsl-layerscape/spl.c
index 2776240..30b5432 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/spl.c
+++ b/arch/arm/cpu/armv8/fsl-layerscape/spl.c
@@ -116,4 +116,33 @@  void board_init_f(ulong dummy)
 	gd->arch.tlb_allocated = gd->arch.tlb_addr;
 #endif	/* CONFIG_SPL_FSL_LS_PPA */
 }
+
+#ifdef CONFIG_SPL_OS_BOOT
+/*
+ * Return
+ * 0 if booting into OS is selected
+ * 1 if booting into U-Boot is selected
+ */
+int spl_start_uboot(void)
+{
+	char s[8];
+
+	env_init();
+	env_get_f("boot_os", s, sizeof(s));
+	if ((s != NULL) && (*s != '0' && *s != 'n' && *s != 'N' &&
+			    *s != 'f' && *s != 'F'))
+		return 0;
+
+	return 1;
+}
+#endif	/* CONFIG_SPL_OS_BOOT */
+#ifdef CONFIG_SPL_LOAD_FIT
+int board_fit_config_name_match(const char *name)
+{
+	/* Just empty function now - can't decide what to choose */
+	debug("%s: %s\n", __func__, name);
+
+	return 0;
+}
+#endif
 #endif /* CONFIG_SPL_BUILD */
diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index 79bd19a..7d8dc44 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -215,7 +215,7 @@  void __asm_switch_ttbr(u64 new_ttbr);
  * @entry_point: kernel entry point
  * @es_flag:     execution state flag, ES_TO_AARCH64 or ES_TO_AARCH32
  */
-void armv8_switch_to_el2(u64 args, u64 mach_nr, u64 fdt_addr,
+void __noreturn armv8_switch_to_el2(u64 args, u64 mach_nr, u64 fdt_addr,
 			 u64 arg4, u64 entry_point, u64 es_flag);
 /*
  * Switch from EL2 to EL1 for ARMv8
diff --git a/arch/arm/lib/spl.c b/arch/arm/lib/spl.c
index 27d6682..ab5d227 100644
--- a/arch/arm/lib/spl.c
+++ b/arch/arm/lib/spl.c
@@ -7,6 +7,7 @@ 
  *
  * SPDX-License-Identifier:	GPL-2.0+
  */
+
 #include <common.h>
 #include <config.h>
 #include <spl.h>
@@ -47,6 +48,15 @@  void __weak board_init_f(ulong dummy)
  * image.
  */
 #ifdef CONFIG_SPL_OS_BOOT
+#ifdef CONFIG_ARM64
+void __noreturn jump_to_image_linux(struct spl_image_info *spl_image)
+{
+	debug("Entering kernel arg pointer: 0x%p\n", spl_image->arg);
+	cleanup_before_linux();
+	armv8_switch_to_el2((u64)spl_image->arg, 0, 0, 0,
+			    spl_image->entry_point, ES_TO_AARCH64);
+}
+#else
 void __noreturn jump_to_image_linux(struct spl_image_info *spl_image)
 {
 	unsigned long machid = 0xffffffff;
@@ -62,4 +72,5 @@  void __noreturn jump_to_image_linux(struct spl_image_info *spl_image)
 	cleanup_before_linux();
 	image_entry(0, machid, spl_image->arg);
 }
+#endif	/* CONFIG_ARM64 */
 #endif