[U-Boot-Users] U-Boot success .. Linux big test

[VanBaren, Gerald (AGRE)]

> -----Original Message-----
> From: Sharad Gupta [mailto:sharad at buckeye.ece.drexel.edu]
> Sent: Tuesday, November 18, 2003 5:36 PM
> To: U-Boot Mailing List
> Subject: [U-Boot-Users] U-Boot success .. Linux big test
> 
> 
> Hi,

[snip] 

> elsewhere ? Rite now, I am not able to figure out where the 
> problem lies,
> the execution hangs somewhere after handling the control to 
> kernel at 0x00
> and it seems my only hope is to put little debug messages 
> (light up the 4
> LEDs on board with the last 2-bytes of instruction address) at every
> function call.

Be VERY careful when lighting LEDs during start up -- a big part of the start up, and definitely the most delicate (i.e. highest probability of problems), is the transition from "no MMU" mode to MMU mode.  During this time, your I/O quite likely won't be mapped or won't be mapped properly unless you hack in some additional MMU mapping (BATs).  

The result, if you are not careful, is that the attempt to toggle LED outputs will CAUSE a crash and will cause a lot of confusion, head-scratching, and chasing down wrong paths.

Umm, someone I know did this... yeah, that's the ticket ;-).

gvb

> Thanks for helping,
> Sharad Gupta




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