LS1046ARDB mount rootfs as tmpfs

srechermann — Tue, 14 Mar 2023 13:32:57 GMT

Hello,

What I want to achieve:

I want to write bootloaders, kernel, dtb and rootfs on my SD Card (in a later stage I want to do the same with the QSPI-Flash). As a rootfs image I want to use a custom-image I create using yocto, that's inheriting from the core-image-minimal and adds a few additional packages (I attached the custom-image recipe). When booting I want to create my rootfs as a tmpfs so that my system is volatile and completely in RAM. I don't know how to archive this and in which format I need my custom-image (cpio, cpio.gz, tar.gz ...). Or if it's necessary/beneficial to combine my kernel, dts and rootfs in a fitImage? In the documentation(https://www.nxp.com/docs/en/supporting-information/QORIQ_LS1046A_BSP_V0-4_REV-A.pdf) I found this:

setenv bootargs "root=/dev/ram0 earlycon=uart8250,mmio,0x21c0500 console=ttyS0,115200"

I guess that's a ramdisk approach which is deprecated and it's more modern and efficient to use a tmpfs (https://www.kernel.org/doc/Documentation/filesystems/ramfs-rootfs-initramfs.txt)? But I'm no expert here and maybe I am misunderstanding something here. Please correct me if I'm wrong and if I can achieve it to have a completely RAM based system using this I'm also happy with this root=/dev/ram0 approach but I also don't know how to modify my current workflow to achieve this approach.

My current workflow having the rootfs as a non volatile SD card partition:
Currently I'm programming my SD card like this:

1. Write bootloader files to the SD card

cd tmp/deploy/images/ls1046ardb bl2_sd_file="atf/bl2_sd.pbl" fip_uboot_file="atf/fip_uboot.bin" fman_ucode_file="fsl_fman_ucode_ls1046_r1.0_106_4_18.bin" image="custom-image-ls1046ardb.tar.gz" kernel="Image" dtb="fsl-ls1046a-rdb-sdk.dtb" # write the bootloader files to the SD card sudo dd if={bl2_sd_file} of=/dev/sdb bs=512 seek=8 sudo dd if={fip_uboot_file} of=/dev/sdb bs=512 seek=2048 sudo dd if={fman_ucode_file} of=/dev/sdb bs=512 seek=18432

2. Create ext2 partition right behind the bootloader files using fdisk and mkfs.ext2

sudo fdisk /dev/sdb n # new partiton p # primary partition 1 #partition number 1 <18432 + number_of_blocks(fsl_fman_ucode_ls1046_r1.0_106_4_18.bin)> # start address +200M # partition size w sudo mkfs.ext2 /dev/sdb1

3. Unpack custom-image.tar.gz to the ext2 partition and copy Image+dtb to /boot directory

sudo mount /dev/sdb1 /mnt/sdcard sudo tar -xzf custom-image-ls1046ardb.tar.gz -C /mnt/sdcard sudo cp Image /mnt/sdcard/boot sudo cp fsl-ls1046a-rdb-sdk.dtb /mnt/sdcard/boot

4. Put SD card in board and switch board on (dip switches are set to SD card boot) and enter uboot prompt

setenv bootcmd 'setenv bootargs root=/dev/mmcblk0p1 rw rootdelay=5 console=ttyS0,115200;mmcinfo;ext2load mmc 0:1 0xa0000000 boot/Image;ext2load mmc 0:1 0xb0000000 /boot/fsl-ls1046a-rdb-sdk.dtb;booti 0xa0000000 - 0xb0000000' boot

Summary

My current workflow works but as already described I want to have my rootfs only in RAM and I don't know what's the best approach to achieve this (not only initramfs, but this would also be ok if it's NOT getting remounted during init process to a rootfs located on SD card). I tried for example using a compressed cpio archive loading it to RAM and passing it as initrd parameter to the booti command but it is not working and I get the error "Wrong Ramdisk Image Format
Ramdisk image is corrupt or invalid".

setenv bootcmd 'setenv bootargs rootfstype=tmpfs rw size=1024M rootdelay=5 console=ttyS0,115200;mmcinfo;ext2load mmc 0:1 0xa0000000 Image;ext2load mmc 0:1 0xb0000000 fsl-ls1046a-rdb-sdk.dtb;ext2load mmc 0:1 0xc0000000 custom-image-initramfs.cpio.gz;booti 0xa0000000 0xc0000000 0xb0000000' boot

Re: LS1046ARDB mount rootfs as tmpfs

srechermann — Tue, 14 Mar 2023 14:43:39 GMT

I tried duplicated the post here https://community.nxp.com/t5/QorIQ/mount-compressed-rootfs-image-located-on-SD-card-as-tmpfs-in-RAM/m-p/1615047#M11383 as I think product forums is not the correct location for my question. But it was marked as spam so maybe it's possible for a moderator to move this question to the correct forum (I think QoriIQ Processing Platforms) and delete this one here?

topic LS1046ARDB mount rootfs as tmpfs in Layerscape

LS1046ARDB mount rootfs as tmpfs

Re: LS1046ARDB mount rootfs as tmpfs