[U-Boot,v2] imx6: apalis: Make the boot process more generic

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 in the boot partion, that's why I've
added write support to the ext4.

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.

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.

Cc: Stefan Agner <stefan.agner@toradex.com>
Cc: Max Krummenacher <max.krummenacher@toradex.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
---
 configs/apalis_imx6_defconfig |  2 ++
 include/configs/apalis_imx6.h | 26 +++++++++++++++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

Changes since v1:

  * Made note about ext4 write support more clear
  * I've removed Kconfig variables and all variables which were coupled to the code
  * I've removed the note about backward compatibility from commit message,
    because I've realized, that this changes are not backward compatible,
    because this patch is switching to part UUID, so the distributions would
    need to provide filesystem with part UUID for rootfs.

Hello Petr,

On Sun, Dec 16, 2018 at 7:31 PM Petr Štetiar <ynezz@true.cz> 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 in the boot partion, that's why I've
> added write support to the ext4.

I wonder if you couldn't instead move the board to use the common
distro environment? Doing that, it allows for easy changing of
bootargs from rootfs (well, technically it can be in a single
partition or not) and easy to hack / understand syslinux.cfg
compatible file.

At OpenEmbedded / Yocto Project, we have been slowly adopting this
more and more as it allows very easy integration and is convenient for
hacking as well. Take a look at Wandboard as an example of it.

Hi Petr,

[this time to the ML]

On 16.12.2018 12:06, 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.

I agree a more flexible boot process would be better. There is distro
boot for that purpose, and I suggest using that by default. We did
enable distro boot in our downstream U-Boot [1] and also make use of it
in the Toradex Easy Installer [2] configuration (run distro_bootcmd). 

Also check doc/README.distro. I think it should not need changes on
OpenWrt side since distro boot loads and executes boot.scr.
Additionally, it also guarantees that some variables are setup (e.g.
devtype, devnum and distro_bootpart) which allows to write generic boot
scripts.


[1]
http://git.toradex.com/cgit/u-boot-toradex.git/commit/include/configs/apalis_imx6.h?h=2016.11-toradex-next&id=a283b85daaefbe11a5a7b53ea06b5b76c54c155a
[2]
http://git.toradex.com/cgit/u-boot-toradex.git/commit/?h=2016.11-toradex-next&id=32c022da358ae016a84cf1dd9bd558a02f979b1a

--
Stefan

> 
> 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 in the boot partion, that's why I've
> added write support to the ext4.
> 
> 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.
> 
> 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.
> 
> Cc: Stefan Agner <stefan.agner@toradex.com>
> Cc: Max Krummenacher <max.krummenacher@toradex.com>
> Signed-off-by: Petr Štetiar <ynezz@true.cz>
> ---
>  configs/apalis_imx6_defconfig |  2 ++
>  include/configs/apalis_imx6.h | 26 +++++++++++++++++++++-----
>  2 files changed, 23 insertions(+), 5 deletions(-)
> 
> Changes since v1:
> 
>   * Made note about ext4 write support more clear
>   * I've removed Kconfig variables and all variables which were
> coupled to the code
>   * I've removed the note about backward compatibility from commit message,
>     because I've realized, that this changes are not backward compatible,
>     because this patch is switching to part UUID, so the distributions would
>     need to provide filesystem with part UUID for rootfs.
> 
> 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..3601891 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 +201,17 @@
>  #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" \
> +	"finduuid=part uuid mmc 0:2 uuid\0" \
> +	"loadbootscript=" \
> +		"load mmc 0:1 ${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 +239,16 @@
>  	"vidargs=mxc_hdmi.only_cea=1 " \
>  		"video=mxcfb0:dev=hdmi,1920x1080M@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 0;" \
> +	   "if run loadbootscript; then " \
> +		   "run bootscript; " \
> +	   "else " \
> +		   "run bootcmd_default; " \
> +	   "fi; "
>  
>  /* Miscellaneous configurable options */
>  #undef CONFIG_SYS_CBSIZE