Daniel Mack zonque at gmail.com
Fri Nov 30 09:27:37 EST 2012

On 30.11.2012 14:58, Naresh Bhat wrote:
> Hi,
> I am using Versatile express target at Daughterboard Site 1:
> V2P-CA15_A7 Cortex A15
> root at arm-cortex-a15:~# kexec -f zImage --dtb=vexpress.dtb
> --append="root=/dev/nfs rw ip=dhcp
> nfsroot=<Host-IP>:/mnt/sda3/nfs/cortexa15/core-image
> console=ttyAMA0,38400n8 nosmp"
> Starting new kernel
> Bye!
> Uncompressing Linux...

That could be just that the new kernel is missing its bootargs cmdline
with the appropriate console= tag. How are you booting the first kernel?
Does you bootloader add a /chosen tag?

Some suggestions:

1. Add a static CMDLINE to the second kernel, so it doesn't rely on that
information being passed from the first on.

2. Try running kexec without the --dtb option. kexec will then walk
/proc/device-tree and build up one dynamically (CONFIG_PROC_DEVICETREE
is needed for that).

3. Try passing --command-line to kexec. Note that this won't work
together with --dtb, as there's currently no code that adds the cmdline
to a dtb binary blob. But with two patches I recently submitted, it
works with the dynamic /proc/device-tree parsing mode.

4. In case you have LEDs connected to GPIOs on your board, configure
them to the heartbeat trigger mode. If that works, you know that the
kernel is actually booting, but just not showing anything on the console.

5. If 4) fails, try to toggle the GPIOs very early in the boot process,
as some sort of interface to trace the control flow, even without a JTAG.

6. In case you have CONFIG_THUMB2_KERNEL set, switch it off. I had no
luck yet booting into a kernel that was compiled in Thumb-2 mode.


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