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I have some difficulties to make initramfs functional with SAMA5D27 SOM1 Evaluation Kit.
I am trying to have a functional initramfs. I first verified that I have a functional linux when used with filesystem on sd.

I used the following bootcmd:

=> fatload mmc 0:1 0x24000000 uramdisk.img; fatload mmc 0:1 0x22000000 zImage; fatload mmc 0:1 0x21000000 board.dtb; bootz 0x22000000 0x24000000 0x21000000;"

I than tried to make initramfs as following: I configured the kernel for initramfs:

CONFIG_BLK_DEV_INITRD=y

CONFIG_INITRAMFS_SOURCE="/media/sdc/at91/tmp/at91/initramfs.cpio"

CONFIG_RD_GZIP=y

CONFIG_RD_BZIP2=y

CONFIG_RD_LZMA=y

CONFIG_RD_XZ=y

CONFIG_RD_LZO=y

CONFIG_RD_LZ4=y

Created ramfs:
cd to rootfs and:

create ramdisk:

# sudo find . | sudo cpio -H newc -o | gzip > ../uramdisk.cpio.gz

# mkimage -A arm -O linux -T ramdisk  -n "Label you want" -d ./ramdisk.img ./uramdisk.img

change bootargs:

setenv bootcmd_boot2 "fatload mmc 0:1 0x23000000 uramdisk.img; fatload mmc 0:1 0x22000000 zImage; fatload mmc 0:1 0x21000000 board.dtb; bootz 0x22000000 0x24000000 0x21000000;"

setenv bootargs "console=ttyS0,115200 atmel.pm_modes=standby,ulp1"

And it still as following:

  => boot

51725888 bytes read in 3093 ms (15.9 MiB/s)

3903560 bytes read in 243 ms (15.3 MiB/s)

26651 bytes read in 14 ms (1.8 MiB/s)

## Loading init Ramdisk from Legacy Image at 24000000 ...

   Image Name:   Label you want

   Image Type:   ARM Linux RAMDisk Image (uncompressed)

   Data Size:    51725824 Bytes = 49.3 MiB

   Load Address: 24000000

   Entry Point:  24000000

   Verifying Checksum ... OK

## Flattened Device Tree blob at 21000000

   Booting using the fdt blob at 0x21000000

   Loading Ramdisk to 24a00000, end 27b54600 ... OK

   Loading Device Tree to 249f6000, end 249ff81a ... OK



Starting kernel ...



Booting Linux on physical CPU 0x0

Linux version 4.7.10+ (user@user-VirtualBox) (gcc version 6.4.0 (Buildroot 2018.02-00001-g3ef3174) ) #6 Wed Nov 7 12:20:42 CST 2018

CPU: ARMv7 Processor [410fc051] revision 1 (ARMv7), cr=10c53c7d

CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache

Machine model: Atmel SAMA5D27 SOM1 EK

Memory policy: Data cache writeback

CPU: All CPU(s) started in SVC mode.

Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 32512

Kernel command line: console=ttyS0,115200  atmel.pm_modes=standby,ulp1

PID hash table entries: 512 (order: -1, 2048 bytes)

Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)

Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)

Memory: 69684K/131072K available (6298K kernel code, 183K rwdata, 1716K rodata, 1024K init, 147K bss, 61388K reserved, 0K cma-reserved)

Virtual kernel memory layout:

    vector  : 0xffff0000 - 0xffff1000   (   4 kB)

    fixmap  : 0xffc00000 - 0xfff00000   (3072 kB)

    vmalloc : 0xc8800000 - 0xff800000   ( 880 MB)

    lowmem  : 0xc0000000 - 0xc8000000   ( 128 MB)

    modules : 0xbf000000 - 0xc0000000   (  16 MB)

      .text : 0xc0008000 - 0xc08d3a18   (9007 kB)

      .init : 0xc0900000 - 0xc0a00000   (1024 kB)

      .data : 0xc0a00000 - 0xc0a2dc20   ( 184 kB)

       .bss : 0xc0a2dc20 - 0xc0a52948   ( 148 kB)

...

mmcblk0: mmc0:0007 SS08G 7.21 GiB

 mmcblk0: p1 p2

**RAMDISK: Couldn't find valid RAM disk image starting at 0.

VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6**

Please append a correct "root=" boot option; here are the available partitions:

0100            8536 ram0  (driver?)

b300         7563264 mmcblk0  driver: mmcblk

  b301          131072 mmcblk0p1 00070105-01

  b302          131072 mmcblk0p2 00070105-02

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

CPU: 0 PID: 1 Comm: swapper Not tainted 4.7.10+ #6

Hardware name: Atmel SAMA5

[<c010cb3c>] (unwind_backtrace) from [<c010a640>] (show_stack+0x10/0x14)

[<c010a640>] (show_stack) from [<c0165920>] (panic+0xc4/0x244)

[<c0165920>] (panic) from [<c09011c8>] (mount_block_root+0x1b0/0x280)

[<c09011c8>] (mount_block_root) from [<c09014a4>] (mount_root+0x120/0x128)

[<c09014a4>] (mount_root) from [<c0901628>] (prepare_namespace+0x17c/0x1c4)

[<c0901628>] (prepare_namespace) from [<c0900df0>] (kernel_init_freeable+0x1b0/0x1c0)

[<c0900df0>] (kernel_init_freeable) from [<c06354e4>] (kernel_init+0x8/0x110)

[<c06354e4>] (kernel_init) from [<c0107498>] (ret_from_fork+0x14/0x3c)

---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

random: nonblocking pool is initialized

I have only 128MByte memory (1Gb), maybe I can't use loadaddress of ramfs same as the address where it is loaded by u-boot, even though it is not compressed ?

One thing definitly worth checking are the load address of your ramfs. It seems to be overloaded partially by zImage.

Your kernel size is 25859560 bytes = 0x018A 95E8. It's loaded at 0x22000000, ends at 0x238A 95E8 thus is loaded overlapping with your ramfs ad 0x23000000

Without knowing your Board in detail i would just try to load ramdist at 0x24000000

Solved as following:

1. bootargs should be added with root=/dev/ram


2. The rootfs from which the cpio is created, should be added with init inside (in /init),

About (2), I should note that that I haven't find anywhere that init should reside in "/init" (it is usually in /sbin/init).