CODEWITHSUNDEEP
linux-kernelu-boot
Tom Xue
Tom Xue

Reputation: 3365

How to boot Linux kernel from u-boot?

My Linux kernel image uImage is in my U-disk. And I want to boot it from U-Boot. Also the device tree file am335x-evm.dtb is in my U-disk. What I did is below:

U-Boot# usb start
(Re)start USB...
USB0:   scanning bus 0 for devices... 1 USB Device(s) found
       scanning usb for storage devices... 1 Storage Device(s) found
U-Boot# fatls usb 0:1
  3821960   uimage
            kit3/
  4065280   modules.tar
            my_modules/
            extra/
            system volume information/
      375   uenv.txt
    40474   am335x-evm.dtb

4 file(s), 4 dir(s)

U-Boot# fatload usb 0:1 0xC0700000 uImage
reading uImage
3821960 bytes read in 2375 ms (1.5 MiB/s)
U-Boot# fatload usb 0:1 0xC0e00000 am335x-evm.dtb
reading am335x-evm.dtb
40474 bytes read in 48 ms (823.2 KiB/s)
U-Boot# bootm 0xC0700000 - 0xC0e00000
## Booting kernel from Legacy Image at c0700000 ...
   Image Name:   Linux-3.12.10-ge35dc10-dirty
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    3821896 Bytes = 3.6 MiB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... OK
## Flattened Device Tree blob at c0e00000
   Booting using the fdt blob at 0xc0e00000
   Loading Kernel Image ... OK
OK
   Using Device Tree in place at c0e00000, end c0e0ce19

Starting kernel ...

And it stops here. How to do? Thanks!

Result: Thanks for everyone who answered in this post! Now I can boot the system by using the image in U-disk. What I do is:

setenv bootargs "console=ttyO0,115200n8 root=/dev/mmcblk0p2 rw rootfstype=ext4 mem=512M coherent_pool=8M loglevel=0 lpj=3317760 rootwait"
usb start; fatls usb 0:1; fatload usb 0:1 0x82000000 uImage-orig-onUSB;fatload usb 0:1 0x80F80000 am335x-evm.dtb;bootm 0x82000000 - 0x80F80000

Without the first sentence, the system can also boot and start the GUI program which will show in a display. But the debug serial port has no reaction any more!

As for the second sentence, if I use the ram address of 0xC0700000 and 0xC0e00000, like this below, then it will stop to load the kernel. The reason should be what sawdust mentioned in his answer. @sawdust

setenv bootargs "console=ttyO0,115200n8 root=/dev/mmcblk0p2 rw rootfstype=ext4 mem=512M coherent_pool=8M loglevel=0 lpj=3317760 rootwait"
usb start; fatls usb 0:1; fatload usb 0:1 0xC0700000 uImage-orig-onUSB;fatload usb 0:1 0xC0e00000 am335x-evm.dtb;bootm 0xC0700000 - 0xC0e00000

Upvotes: 4

Views: 29666

Answers (2)

sawdust
sawdust

Reputation: 17077

Despite the message "Starting kernel ...", the kernel has not actually started executing (because the image has to be first relocated and also uncompressed), and consequently enabling earlyprintk will have no effect yet.
What does look suspect are the RAM addresses.

The typical "am33xx-evm" board only has 512MB of RAM starting at 0x80000000.
Yet you are trying to use RAM addresses from 0xC0700000 to 0xC0E0CE19 where physical memory should not exist.
Obviously the kernel and the device tree are not loaded properly.

Instead of 

fatload usb 0:1 0xC0700000 uImage
fatload usb 0:1 0xC0e00000 am335x-evm.dtb
bootm 0xC0700000 - 0xC0e00000

try using 

fatload usb 0:1 0x80200000 uImage 
fatload usb 0:1 0x80e00000 am335x-evm.dtb
bootm 0x80200000 - 0x80e00000

Upvotes: 5

Eugene Sh.
Eugene Sh.

Reputation: 18381

The booting sequence looks fine. The kernel and the device tree are loaded properly. The problem seems to be in the kernel itself. Probably it is just not built with the right settings. Specifically the console device and early printk facility should be enabled. Also check your bootargs.

Upvotes: 2

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