How to load kernel and rootfs into QSPI Flash in I.MX8MPLUS

[NXP_USER_05]

Hi,

We are Using I.MX8MPLUS Custom board. In our board we have QSPI flash with 32MB size. Up to u-boot Successfully booted in QSPI mode .

1. How to load kernel and rootfs into QSPI Flash in i.MX8MPLUS.

2. In our i.MX8MPLUS Custom board we don't have supported devices like eMMC, SD ,Nand and USB. without all these how can we load the kernel and rootfs.

3. Is there any Procedure for loading kernel and rootfs into QSPI flash without the SD card and eMMC.

[Adele]

@NXP_USER_05 

You can check the following link, it might help you. 

And I have sent you about this in private message to you. 

https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/all-bootloader-device-tree-Linux-kernel-...

[NXP_USER_05]

Hi @Adele ,

We are working with the i.MX8M Plus EVK, which has 32 MB QSPI flash.
Our goal is to boot U-Boot, Linux kernel, device tree, and initramfs (rootfs.img ) entirely from QSPI flash.

We are able to successfully boot:

U-Boot (from flash.bin)

Linux kernel (Image.gz)

Device Tree (imx8mp-evk.dtb)

However, we are facing issues when loading and using the initramfs/rootfs image from QSPI flash. The kernel starts successfully, but the kernel hangs at Waiting for removable media.... see the below log attached.

-----Flash Layout and Image Sizes----------------

QSPI flash size: 32 MB

flash.bin (U-Boot + SPL) ~2.3 MB
Image.gz (Kernel) ~13.5 MB
imx8mp-evk.dtb ~86 KB
rootfs.img ~12.6 MB

----QSPI Offset Layout----------
flash.bin @ 0x00000000
Image.gz @ 0x00240000
imx8mp-evk.dtb @ 0x01000000
rootfs.img @ 0x01080000

------Programming files into QSPI (from SD card)---------
sf probe 0
sf erase 0x0 0x2000000

fatload mmc 1 ${loadaddr} flash.bin
sf write ${loadaddr} 0x0 ${filesize}

fatload mmc 1 ${loadaddr} Image.gz
sf write ${loadaddr} 0x240000 ${filesize}

fatload mmc 1 ${loadaddr} imx8mp-evk.dtb
sf write ${loadaddr} 0x1000000 ${filesize}

fatload mmc 1 ${loadaddr} rootfs.img # initramfs (cpio.gz)
sf write ${loadaddr} 0x1080000 ${filesize}

------After flashing,power-cycle the board--------------

After boot from u-boot,setting the env variables for Linux kernel (Image.gz),Device Tree (imx8mp-evk.dtb),rootfs.img.

sf probe 0
setenv loadaddr 0x40480000 // kernel
setenv fdt_addr 0x43000000 //dtb
setenv initrd_addr 0x43800000 //rootfs
setenv kernel_comp_addr_r 0x50000000
setenv kernel_comp_size 0x04000000

sf read ${loadaddr} 0x240000 0xCD3CE2

sf read ${fdt_addr} 0x1000000 0x14360

sf read ${initrd_addr} 0x1080000 0xC04DB0

setenv bootargs "console=ttymxc1,115200 root=/dev/ram0 rw"

setenv bootcmd 'sf probe 0; sf read ${loadaddr} 0x240000 0xCD3CE2; sf read ${fdt_addr} 0x1000000 0x14360; sf read ${initrd_addr} 0x1080000 0xC04DB0; booti ${loadaddr} ${initrd_addr} ${fdt_addr}'

saveenv

-----------------------Question 1------------------------------------
1.With SD card Wic file working fine with partitions (Boot/Root).
2.We genarated Two yocto images
==> 1.bitbake core-image-minimal-initramfs (generated initramfs.cpio.gz) this cpio.gx converted into rootfs.img by using this cmd mkimage -A arm -O linux -T ramdisk -d <gzipped_rootfs> <Ramdisk_name> (from linux user guide)
==>2.Also generated tiny rootfs from yocto generated using bitbake core-image-tiny. core-image-tiny-imx8mp-evk.tar.zst this tar extracted into EXT4 partition in SD card succussfully loading tiny rootfs .
3.But as said in 2nd point rootfs.img also put into EXT4 root partition in SD card but not loading the rootfs.

-----------------------Question 2------------------------------------
1.Is this the correct approach to boot an initramfs (rootfs.img) directly from QSPI on i.MX8M Plus EVK?

-----------------------Question 3------------------------------------
3.Is there any recommended NXP reference image for booting kernel and initramfs entirely from QSPI on i.MX8MP(Linux kernel (Image.gz),Device Tree (imx8mp-evk.dtb),rootfs.img) ?

[Bio_TICFSL]

Hello,

# How to Load Kernel and RootFS into QSPI Flash on i.MX8MPLUS Custom Board

Based on your custom board configuration with a 32MB QSPI flash and no eMMC, SD, NAND or USB devices, here are the recommended approaches:

## QSPI Flash Boot Solution

While your U-Boot has successfully booted from QSPI, there are important limitations to consider:

1. The 32MB QSPI flash is typically not large enough to hold a complete Linux rootFS. QSPI flash on i.MX8M Plus is primarily designed for storing U-Boot/bootloader components.

2. A practical approach is to implement a hybrid solution:
- Store U-Boot in QSPI flash (already accomplished)
- Store the kernel and device tree blob (DTB) in QSPI flash
- Implement a minimal initramfs for basic functionality

## Implementation Steps

1. Generate the QSPI bootable image using the imx-mkimage tool:
```
make SOC=iMX8MP flash_evk_flexspi
```

2. Create partitions in QSPI flash with approximate sizes:
- U-Boot: 512KB (already flashed)
- Linux kernel: ~9MB
- Device tree blob: ~64KB
- U-Boot environment: ~64KB
- InitramFS (minimal rootFS): ~22MB

3. Configure U-Boot to load kernel and DTB from QSPI flash:
```
sf probe
sf read ${loadaddr} 0x80000 0x900000 # Read kernel from QSPI
sf read ${fdt_addr} 0x980000 0x10000 # Read DTB from QSPI
```

4. Create a minimal initramfs with essential tools and utilities that will fit within the available space.

5. For more complex applications, consider implementing network boot support (NFS) for a full rootFS.

This approach provides a viable solution for booting your system with the existing hardware constraints.

Regards

[NXP_USER_05]

Hi @Bio_TICFSL ,

As You said Upto 3rd point able to  done, but 4th point not getting.

We are working with the i.MX8M Plus EVK, which has 32 MB QSPI flash.
Our goal is to boot U-Boot, Linux kernel, device tree, and initramfs (rootfs.img ) entirely from QSPI flash.

We are able to successfully boot:

U-Boot (from flash.bin)

Linux kernel (Image.gz)

Device Tree (imx8mp-evk.dtb)

However, we are facing issues when loading and using the initramfs/rootfs image from QSPI flash. The kernel starts successfully, but the kernel hangs at Waiting for removable media....   ## see the below attached Log

-----Flash Layout and Image Sizes----------------

QSPI flash size: 32 MB

flash.bin (U-Boot + SPL) ~2.3 MB
Image.gz (Kernel) ~13.5 MB
imx8mp-evk.dtb ~86 KB
rootfs.img ~12.6 MB

----QSPI Offset Layout----------
flash.bin @ 0x00000000
Image.gz @ 0x00240000
imx8mp-evk.dtb @ 0x01000000
rootfs.img @ 0x01080000

------Programming files into QSPI (from SD card)---------
sf probe 0
sf erase 0x0 0x2000000

fatload mmc 1 ${loadaddr} flash.bin
sf write ${loadaddr} 0x0 ${filesize}

fatload mmc 1 ${loadaddr} Image.gz
sf write ${loadaddr} 0x240000 ${filesize}

fatload mmc 1 ${loadaddr} imx8mp-evk.dtb
sf write ${loadaddr} 0x1000000 ${filesize}

fatload mmc 1 ${loadaddr} rootfs.img # initramfs (cpio.gz)
sf write ${loadaddr} 0x1080000 ${filesize}

------After flashing,power-cycle the board--------------

After boot from u-boot,setting the env variables for Linux kernel (Image.gz),Device Tree (imx8mp-evk.dtb),rootfs.img.

sf probe 0
setenv loadaddr 0x40480000 // kernel
setenv fdt_addr 0x43000000 //dtb
setenv initrd_addr 0x43800000 //rootfs
setenv kernel_comp_addr_r 0x50000000
setenv kernel_comp_size 0x04000000

sf read ${loadaddr} 0x240000 0xCD3CE2

sf read ${fdt_addr} 0x1000000 0x14360

sf read ${initrd_addr} 0x1080000 0xC04DB0

setenv bootargs "console=ttymxc1,115200 root=/dev/ram0 rw"

setenv bootcmd 'sf probe 0; sf read ${loadaddr} 0x240000 0xCD3CE2; sf read ${fdt_addr} 0x1000000 0x14360; sf read ${initrd_addr} 0x1080000 0xC04DB0; booti ${loadaddr} ${initrd_addr} ${fdt_addr}'

saveenv

-----------------------Question 1------------------------------------
1.With SD card Wic file working fine with partitions (Boot/Root).
2.We genarated Two yocto images
==> 1.bitbake core-image-minimal-initramfs (generated initramfs.cpio.gz) this cpio.gx converted into rootfs.img by using this cmd mkimage -A arm -O linux -T ramdisk -d <gzipped_rootfs> <Ramdisk_name> (from linux user guide)
==>2.Also generated tiny rootfs from yocto generated using bitbake core-image-tiny. core-image-tiny-imx8mp-evk.tar.zst this tar extracted into EXT4 partition in SD card succussfully loading tiny rootfs .
3.But as said in 2nd point rootfs.img also put into EXT4 root partition in SD card but not loading the rootfs.

-----------------------Question 2------------------------------------
1.Is this the correct approach to boot an initramfs (rootfs.img) directly from QSPI on i.MX8M Plus EVK?

-----------------------Question 3------------------------------------
3.Is there any recommended NXP reference image for booting kernel and initramfs entirely from QSPI on i.MX8MP(Linux kernel (Image.gz),Device Tree (imx8mp-evk.dtb),rootfs.img) ?

Thank You.

[NXP_USER_05]

Hi @Bio_TICFSL ,

Hi @Manuel_Salas 

I am working on an i.MX8M Plus DDR4 custom board and I am able to successfully boot the system entirely from QSPI flash (32MB).

My current boot components are:

flash.bin (U-Boot)

Image.gz (Linux kernel)

imx8mp-ddr4-evk.dtb

core-image-minimal-initramfs.cpio.gz

Since my board does not have SD card or eMMC, I am using initramfs as the root filesystem.

Now I want to include gcc inside core-image-minimal-initramfs.cpio.gz, so that I can compile applications directly on the target without relying on any external storage.

Changed the conf/local.conf and then build using command

      $bitbake core-image-minimal-initramfs

Also attached the local.conf file for your reference.

It generated core-image-minimal-initramfs.cpio.gz but in bin/ and usr/bin respective folders gcc is not present and getting like below after booting kernel and cpio.gz.

~ # gcc
/bin/sh: gcc: not found

~ # ls
bin dev home init.d media proc run sys usr
boot etc init lib mnt root sbin tmp var

Could you please advise:

What is the correct Yocto method to include gcc in an initramfs image?

Are there any recommended configurations or limitations when using gcc inside initramfs (RAM usage, image size, etc.)?

Any guidance or reference to NXP-supported Yocto practices would be very helpful.

Thank You.