early kernel debugging

[Feng Kan]

Hi:
 
Did you try the early kernel printk option in kernel hacking. It can 
give some
very helpful information. Make sure the address for the physical uart 
address is
passed in correctly.

Feng


Tirumala Reddy Marri wrote:
> I am not sure if I understand correctly. But Looks like you are not
> passing the device tree along with kernel image and RAMDISK(you may not
> need it if  you are using NFS mount). You boot command should some what
> look like this "bootm kernel_addr ramdisk_addr devtree_addr" or "bootm
> kernel_addr - devtree_addr" . If you are already doing that I would
> check my bootargs for correct params.
>
> -----Original Message-----
> From: linuxppc-dev-bounces+tmarri=amcc.com at ozlabs.org
> [mailto:linuxppc-dev-bounces+tmarri=amcc.com at ozlabs.org] On Behalf Of
> Yigal Goldberger
> Sent: Thursday, April 02, 2009 1:06 PM
> To: linuxppc-dev at ozlabs.org
> Subject: early kernel debugging
>
>
> Hi All,
> I'm using u-boot to boot kernel 2.6.24.2 on a powerpc based board .
> I see that after uncompressing the kernel it hangs.
> I found a location (System.map) I think corresponds to the __log_buf (my
> SDRAM starts at physical address 0 (and u-boot performs -> Load Address:
> 00000000 Entry Point: 00000000) .
> So I just removed the leading C0xxxxxx from the address leaving xxxxxx .
> And that's where I looked . 
> I did see 2 error messages (though they were somewhat corrupt) the first
> designated a memory fault and the second a kernel oops at some address.
> I looked this address up on System.map and it's somewhere inside prom.c
> in of_scan_flat_dt( ) . 
>
> I have a few question at this point :
> A)Am I looking at the right memory location for __log_buf ?
> B)What is printed to the buffer (printk's of what verbose level ?)
> C)In a previous kernel version 2.6.14 I don't remember explicitly using
> a flat device tree or pointing at such a tree through the bootm command)
> , but I used the ARCH=ppc then as opposed to ARCH=powerpc Now .
> I see a lot of stuff regarding the need to provide such a data structure
> upon booting via bootm .Do I need to explicitly prepare such a data
> structure and provide a pointer to it via bootm ?
> Might this be the cause for this early hang ?
>
> Best Regards,
> Yigal Goldberger. 
>
>
>       
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