[U-Boot] [PATCH] imx6: apalis: Make the boot process more generic

Fri Dec 14 13:55:54 UTC 2018

Hi Petr,

On 01/12/18 14:00, Petr Štetiar wrote:
> I'm preparing support for Apalis imx6 boards in OpenWrt and I've ended
> up with quite huge patchset against upstream U-Boot 2018.03, so I'm
> trying to propose more generic way of boot process handling.
> 
> In OpenWrt we usually have kernel, dtbs and U-Boot boot script in boot
> partition with ext4fs, so for some use cases it would be handy to be
> able to replace some of the files
> 
> I've added TDX_APALIS_IMX6_BOOT_PART and TDX_APALIS_IMX6_ROOT_PART
> config variables so this could be distro specific and overridden.
> 
> I've added `set_blkcnt` environment variable which is needed for every
> `mmc write` command as we need to always specify size in block count.
> This is copy&pasted from official Toradex's flashing scripts, so all the
> credits for this work belongs to them.
> 
> Currently the rootfs location is passed via mmcblk number and the
> problem with this approach is that the mmcblk number for the boot device
> changes depending on the kernel version and imx6 SoC type.  In order to
> avoid such issues, use the UUID method to specify the rootfs location.
> 
> I've added new boot sequence, where we first try to load and run boot
> script defined in the new `script` variable, so the boot process could
> be more generic and overridden by the distro. When the boot script isn't
> loaded, it will use the previous boot sequence so it should be backward
> compatible.
> 
> For the recovery purposes and better end user experience I've added boot
> from SDP as the last boot command if every other boot option fails. I
> plan to use SDP as official flashing/recovery procedure in OpenWrt for
> Apalis imx6 boards.
> 
> I've copy&pasted almost everything from the `f086812a mx6sxsabresd: Use
> PARTUUID to specify the rootfs location` commit, so credits for the rest
> of this patch belongs to Fabio.
> 

I have read your arguments and I can understand them. But anyway, let me
 say that this is also in the wrong direction - I know this is not an
issue of apalis, but it is a general topic.

The boot process, as set of scripts and variables to be evalueated to
boot a board, can be in some times very project specific. The changes
you propose goes into the environment - a default environment instead of
an "initialized" environment.

We had a long thread last month, see :

https://lists.denx.de/pipermail/u-boot/2018-November/348379.html

Since a long time, we accepted to introduce in CONFIG_EXTRA_ENV any
change possible. Anyway, the first environment should not linked
together with code, even if this an easy way to do. Any change to the
environment requires to change u-boot code, and so on.

In your case, you add also some Kconfig and this adds another dependecy
to the bootloader. Much better will be if the initialized environment is
not linked directly to the code, and it can be arranged in some way just
to have a single binary if secure boot is used and the first environment
should be signed. See also Wolfgang's answer to this topic at:

	https://lists.denx.de/pipermail/u-boot/2018-November/348569.html

I think we get the limit of current mechanism: each change (even the
number of partition) requires to change the U-Boot source and to provide
another binary. This does not makes sense, because U-Boot was not
changed, just the data that U-Boot uses to starts an OS.

Best regards,
Stefano

> Cc: Stefan Agner <stefan.agner at toradex.com>
> Cc: Max Krummenacher <max.krummenacher at toradex.com>
> Signed-off-by: Petr Štetiar <ynezz at true.cz>
> ---
>  board/toradex/apalis_imx6/Kconfig | 15 +++++++++++++++
>  configs/apalis_imx6_defconfig     |  2 ++
>  include/configs/apalis_imx6.h     | 29 ++++++++++++++++++++++++-----
>  3 files changed, 41 insertions(+), 5 deletions(-)
> 
> diff --git a/board/toradex/apalis_imx6/Kconfig b/board/toradex/apalis_imx6/Kconfig
> index 14f8c10..584bc9f 100644
> --- a/board/toradex/apalis_imx6/Kconfig
> +++ b/board/toradex/apalis_imx6/Kconfig
> @@ -50,6 +50,21 @@ config TDX_APALIS_IMX6_V1_0
>  	    otherwise the UARTs are configuered in DTE mode.
>  	default n
>  
> +config TDX_APALIS_IMX6_BOOT_PART
> +	int "Partition number to use for boot filesystem"
> +	default 1
> +	help
> +	  The partition number to use for boot filesystem this is the
> +	  partition that typically contains boot.scr, DTBs, uImage etc.
> +
> +config TDX_APALIS_IMX6_ROOT_PART
> +	int "Partition number to use for root filesystem"
> +	default 2
> +	help
> +	  The partition number to use for root filesystem this is the
> +	  partition that is typically specified with root=/dev/sdaX or
> +	  which gets converted into a root=PARTUUID=some_uuid.
> +
>  source "board/toradex/common/Kconfig"
>  
>  endif
> diff --git a/configs/apalis_imx6_defconfig b/configs/apalis_imx6_defconfig
> index 133fc1a..279d39f 100644
> --- a/configs/apalis_imx6_defconfig
> +++ b/configs/apalis_imx6_defconfig
> @@ -39,6 +39,7 @@ CONFIG_CMD_DFU=y
>  CONFIG_CMD_GPIO=y
>  CONFIG_CMD_I2C=y
>  CONFIG_CMD_MMC=y
> +CONFIG_CMD_PART=y
>  CONFIG_CMD_USB=y
>  CONFIG_CMD_USB_SDP=y
>  CONFIG_CMD_USB_MASS_STORAGE=y
> @@ -48,6 +49,7 @@ CONFIG_CMD_PING=y
>  CONFIG_CMD_BMP=y
>  CONFIG_CMD_CACHE=y
>  CONFIG_CMD_EXT4=y
> +CONFIG_CMD_EXT4_WRITE=y
>  CONFIG_CMD_FAT=y
>  CONFIG_CMD_FS_GENERIC=y
>  CONFIG_ENV_IS_IN_MMC=y
> diff --git a/include/configs/apalis_imx6.h b/include/configs/apalis_imx6.h
> index 135b3c9..9af5b29 100644
> --- a/include/configs/apalis_imx6.h
> +++ b/include/configs/apalis_imx6.h
> @@ -142,9 +142,9 @@
>  	"imx6q-colibri-cam-eval-v3.dtb fat 0 1"
>  
>  #define EMMC_BOOTCMD \
> -	"emmcargs=ip=off root=/dev/mmcblk0p2 rw,noatime rootfstype=ext3 " \
> +	"emmcargs=ip=off root=PARTUUID=${uuid} rw,noatime rootfstype=ext3 " \
>  		"rootwait\0" \
> -	"emmcboot=run setup; " \
> +	"emmcboot=run setup; run finduuid;" \
>  		"setenv bootargs ${defargs} ${emmcargs} ${setupargs} " \
>  		"${vidargs}; echo Booting from internal eMMC chip...; "	\
>  		"run emmcdtbload; load mmc 0:1 ${kernel_addr_r} " \
> @@ -201,10 +201,20 @@
>  #define FDT_FILE "imx6q-apalis_v1_0-eval.dtb"
>  #endif
>  #define CONFIG_EXTRA_ENV_SETTINGS \
> -	"bootcmd=run emmcboot ; echo ; echo emmcboot failed ; " \
> +	"script=boot.scr\0" \
> +	"mmcbootdev=" __stringify(CONFIG_SYS_MMC_ENV_DEV) "\0" \
> +	"bootpart=" __stringify(CONFIG_TDX_APALIS_IMX6_BOOT_PART) "\0" \
> +	"rootpart=" __stringify(CONFIG_TDX_APALIS_IMX6_ROOT_PART) "\0" \
> +	"finduuid=part uuid mmc ${mmcbootdev}:${rootpart} uuid\0" \
> +	"loadbootscript=" \
> +		"load mmc ${mmcbootdev}:${bootpart} ${loadaddr} ${script};\0" \
> +	"bootscript=echo Running bootscript from mmc ...; " \
> +		"source\0" \
> +	"bootcmd_default=run emmcboot ; echo ; echo emmcboot failed ; " \
>  		"run nfsboot ; echo ; echo nfsboot failed ; " \
>  		"usb start ;" \
> -		"setenv stdout serial,vga ; setenv stdin serial,usbkbd\0" \
> +		"setenv stdout serial,vga ; setenv stdin serial,usbkbd;" \
> +		"sdp 0\0" \
>  	"boot_file=uImage\0" \
>  	"console=ttymxc0\0" \
>  	"defargs=enable_wait_mode=off vmalloc=400M\0" \
> @@ -232,7 +242,16 @@
>  	"vidargs=mxc_hdmi.only_cea=1 " \
>  		"video=mxcfb0:dev=hdmi,1920x1080M at 60,if=RGB24 " \
>  		"video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off " \
> -		"fbmem=32M\0 "
> +		"fbmem=32M\0 " \
> +	"set_blkcnt=setexpr blkcnt ${filesize} + 0x1ff && setexpr blkcnt ${blkcnt} / 0x200\0"
> +
> +#define CONFIG_BOOTCOMMAND \
> +	   "mmc dev ${mmcbootdev};" \
> +	   "if run loadbootscript; then " \
> +		   "run bootscript; " \
> +	   "else " \
> +		   "run bootcmd_default; " \
> +	   "fi; "
>  
>  /* Miscellaneous configurable options */
>  #undef CONFIG_SYS_CBSIZE
> 

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