Mailinglist Archive: opensuse-arm (170 mails)

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Re: [opensuse-arm] u-boot+EFI: how to debug grub2?
  • From: "Matwey V. Kornilov" <matwey.kornilov@xxxxxxxxx>
  • Date: Sun, 13 Mar 2016 16:39:58 +0300
  • Message-id: <>
2016-03-13 16:21 GMT+03:00 Alexander Graf <agraf@xxxxxxx>:

On 13.03.16 14:13, Matwey V. Kornilov wrote:
2016-03-13 15:09 GMT+03:00 Alexander Graf <agraf@xxxxxxx>:

On 13.03.16 12:30, Alexander Graf wrote:

Am 13.03.2016 um 11:56 schrieb Matwey V. Kornilov


I am trying to boot on Phytec Wega board (TI AM33xx based) with
u-boot+EFI+grub2 and just see

Booting `openSUSE-Tumbleweed-ARM-JeOS-wega [ VMX ]'

Loading linux.vmx...
Loading initrd.vmx...

and then board is rebooted after some time (I think, by watchdog).
I am sure that kernel console parameter is correct.

Before EFI was introduced to u-boot, I had booted this board
successfully. Is there a simple way to somehow understand what is going
wrong here?

My guess is that the device tree doesn't get loaded. Do you see a warning
about it on serial? Try to add a line in grub2 to manually select the
device tree:

Press e (edit current entry)
at the end, add a new line saying "devicetree /boot/dtb/foo.dtb"
Press ctrl-x (or f10) to boot

If that makes it work, the default U-Boot environment does not set the
"fdtfile" variable. Add it to the env (in your board header) and you
should be set :).

If that still doesn't help, try to add an earlycon parameter to the
kernel command line. If that still doesn't show you anything at all, you
can grab the kernel log_buf using md.b from the u-boot command line
after reset, but let's see whether you get to the kernel log / fix the
issue without that first :).

in I found the following:

c12bfc30 b __log_buf

I am not sure how to properly map this address when I know that kernel
is loaded at 0x80008000

That means that the address should be


Try to md.b from there after reset and you should spot the kernel output

When I attach panic=-1 to kernel, the pause is about 15 seconds
(instead of 60 earlier), so I think that this parameter is taken into
However, in any case the buffer log_buf is filled with zeroes
according to md.b. Maybe u-boot resets the memory on start?

If you want to debug grub efi specifics, you can do

Press e (edit current entry)
at the top, add a new line saying "set debug=all"
Pres ctrl-x (or f10) to boot

That should give you all the glorious details from grub2 on what exactly
it's doing.

At the end of long output I see the following:

??, er/arm/linux.c:238: atag: 0x88000000, 90, edfe0dd0, ?
loader/arm/linux.c:246: Kernel at: 0x80008000
loader/arm/linux.c:184: linux_args: 'BOOT_IMAGE=/boot/linux.vmx
plymouth.enable=0 console=ttyS0,115200n8 rootfstype=ramfs showopts'
loader/arm/linux.c:199: Initrd @ 0x8800b000-0x8acfe33c
loader/arm/linux.c:215: FDT updated for Linux boot
loader/arm/linux.c:255: FDT @ 0x0x88000000
loader/arm/linux.c:267: Jumping to Linux...

It seems that grub starts the kernel. I also checked that fdt fits
into 0xb000 bytes.


mmio mode prints the single one character '['
mmio32 mode prints some garbage
mmio32be prints one space character.

Phew. Well, at least it means that Linux is coming up... and doesn't
like something.


With best regards,
Matwey V. Kornilov
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