How do I boot a Yocto generated image on the MX6 SABRE devices

Question

Question: What output should I expect from core-image-minimal the U-boot platform, running on i.MX6 quad core Sabre devkit?

I can see a splash screen with the Freescale logo, but then the display goes blank. I was expecting some kind of boot-sequence and a U-Boot> command interface.

I also see from uboot_mx6x.pdf the following: By default, U-Boot is configured to display the command prompt and receive serial keyboard input on certain UART ports with 115,200-8-N-1 settings.

Question: Where is this defined? How do I change it? How do I listen to this?

I followed a guide on NXP forums to start understanding Yocto and u-boot. I have installed and followed the procedures from here.

I have used the command:

$ bitbake core-image-minimal

Loading cache: 100%     |#######################################| Time: 0:00:00
Loaded 2274 entries from dependency cache.
NOTE: Resolving any missing task queue dependencies

Build Configuration:
BB_VERSION           = "1.36.0"
BUILD_SYS            = "x86_64-linux"
NATIVELSBSTRING      = "universal"
TARGET_SYS           = "arm-fslc-linux-gnueabi"
MACHINE              = "imx6qdlsabresd"
DISTRO               = "fslc-framebuffer"
DISTRO_VERSION       = "2.4"
TUNE_FEATURES        = "arm armv7a vfp thumb neon callconvention-hard"
TARGET_FPU           = "hard"
meta                 
meta-poky            = "HEAD:fdeecc901196bbccd7c5b1ea4268a2cf56764a62"
meta-oe              
meta-multimedia      = "HEAD:dacfa2b1920e285531bec55cd2f08743390aaf57"
meta-freescale       = "HEAD:d6141ea291a1ac9ab8fb1dd1110d408f840fda57"
meta-freescale-3rdparty = "HEAD:62de01743c9233ea718de22991c47b73a78b4857"
meta-freescale-distro = "HEAD:0ec6d7e206705702b5b534611754de0787f92b72"

Initialising tasks: 100%     |###################################| Time: 0:00:04
NOTE: Executing SetScene Tasks
NOTE: Executing RunQueue Tasks
NOTE: Tasks Summary: Attempted 3032 tasks of which 2366 didn't need to be     rerun and all succeeded.
NOTE: Writing buildhistory

$ wic create imx-uboot-spl-bootpart -e core-image-minimal

INFO: Building wic-tools...

Previous bitbake instance shutting down?, waiting to retry...
Loading cache: 100% |###################################| Time: 0:00:00
Loaded 2274 entries from dependency cache.
NOTE: Resolving any missing task queue dependencies

Build Configuration:
BB_VERSION           = "1.36.0"
BUILD_SYS            = "x86_64-linux"
NATIVELSBSTRING      = "universal"
TARGET_SYS           = "arm-fslc-linux-gnueabi"
MACHINE              = "imx6qdlsabresd"
DISTRO               = "fslc-framebuffer"
DISTRO_VERSION       = "2.4"
TUNE_FEATURES        = "arm armv7a vfp thumb neon callconvention-hard"
TARGET_FPU           = "hard"
meta                 
meta-poky            = "HEAD:fdeecc901196bbccd7c5b1ea4268a2cf56764a62"
meta-oe              
meta-multimedia      = "HEAD:dacfa2b1920e285531bec55cd2f08743390aaf57"
meta-freescale       = "HEAD:d6141ea291a1ac9ab8fb1dd1110d408f840fda57"
meta-freescale-3rdparty = "HEAD:62de01743c9233ea718de22991c47b73a78b4857"
meta-freescale-distro = "HEAD:0ec6d7e206705702b5b534611754de0787f92b72"

Initialising tasks: 100% |#####################################| Time: 0:00:00
NOTE: Executing SetScene Tasks
NOTE: Executing RunQueue Tasks
NOTE: Tasks Summary: Attempted 380 tasks of which 380 didn't need to be rerun and all succeeded.
NOTE: Writing buildhistory
INFO: Creating image(s)...

INFO: The new image(s) can be found here:
  ./imx-uboot-spl-bootpart-201804091703-mmcblk.direct

The following build artifacts were used to create the image(s):
  ROOTFS_DIR:                   /media/mattis/7228221d-c3f3-424e-8443-8e97176c6a6d/sandbox/fsl-community-bsp/tmp.wic.yc_b166n/rootfs_copy
  BOOTIMG_DIR:                  /media/mattis/7228221d-c3f3-424e-8443-8e97176c6a6d/sandbox/fsl-community-bsp/build/tmp/work/imx6qdlsabresd-fslc-linux-gnueabi/core-image-base/1.0-r0/recipe-sysroot/usr/share
  KERNEL_DIR:                   /media/mattis/7228221d-c3f3-424e-8443-8e97176c6a6d/sandbox/fsl-community-bsp/build/tmp/deploy/images/imx6qdlsabresd
  NATIVE_SYSROOT:               /media/mattis/7228221d-c3f3-424e-8443-8e97176c6a6d/sandbox/fsl-community-bsp/build/tmp/work/armv7at2hf-neon-fslc-linux-gnueabi/wic-tools/1.0-r0/recipe-sysroot-native

INFO: The image(s) were created using OE kickstart file:
  /media/mattis/7228221d-c3f3-424e-8443-8e97176c6a6d/sandbox/fsl-community-bsp/sources/meta-freescale/wic/imx-uboot-spl-bootpart.wks

Lastly I use the command:

dd if=imx-uboot-spl-bootpart-201804091703-mmcblk.direct of=/dev/sdb

After this process, I take the SDCard, and plug it into my sabre development kit, this then boots up the splash screen, after which nothing happens.

Answer 1

To answer your questions:

1. You should expect to see u-boots output, followed by the kernel's console output, and finally a login prompt.

2. The console is defined by the SERIAL_CONSOLES variable. You would listen to this by connecting a serial cable to the board and using a program like minicom.

Reading into your questions a bit, I believe the image you are putting on the SD card is not going to work. I do not know much about imx-uboot-spl-bootpart other than how it is described in the kickstart file, and can't say for sure which boards it is compatible with.

You should be able to use the default wic image that is generated once the build is complete. It looks like you are building from Yocto 2.4 Rocko, so once your build is finished you will have two files located here:

$BUILD_DIR/tmp/deploy/images/imx6qdlsabresd/...  
core-image-minimal-imx6qdlsabresd.wic  
core-image-minimal-imx6qdlsabresd.wic.bmap

If these files do not exist you can create them by adding this line to your local.conf file:

IMAGE_FSTYPES += "wic wic.bmap"

I would recommend using bmap-tools instead of dd as it will save you a lot of time.

In your example the command should look like this:

 bmaptool copy /path/to/core-image-minimal-imx6qdlsabresd.wic /dev/sdb

That image should boot and you will be given the chance to stop u-boot and land at the u-boot prompt.

It looks like the default Freescale image is currently wic.gz, which bmap-tools should handle as well.