[U-Boot-Users] SDRAM init problem? Was Re: uboot 1.1.2 problem

[Sam Song]

Scott McNutt <smcnutt at psyent.com> wrote:
> > Just wanna to confirm one thing. If one board's 
> > SDRAM init was good enough but with poor layout
> > (Layout design or PCB Processing), it would crash
> > like this?
> 
> Yes, if your clock signals were not routed cleanly
> ... but re-check your SDRAM init first.

Thanks. Actually, it involves the grey area which a 
probelm was supposed to produce by hardware or 
software. The golden role is to check SW first.

[snip]
> The good part is that u-boot remains stable (due to
> some handy design decisions) ... and the POST cache
> tests are a great starting point to determine if the
> problem exists ... in a deterministic manner ;-)

Really a nice explanation and experience share. 

I have been thinking one puzzle related u-boot itself.
I noticed that sometimes u-boot would hang after 
relocation on my board. The chance is slim but have 
an effect on normal operation. Maybe 1 out of 10 
times. Especially when power down and on in a short 
interval like no more than 1 minute. I don't know 
whether this symptom is due to SDRAM init problem.

My wild guess is some elements like capacitances 
don't discharge enough to restore the original state
they should be. 

U-Boot 1.0.0 (Aug 20 2004 - 21:11:30)
&nbsp;
CPU: PPC823EZTnnB2 at 48 MHz: 16 kB I-Cache 8 kB Cache
Board: DMTXX
DRAM:  128 MB 

Code reached to relocate_code()->board_init_r().
Stoped before flash_init().

Does anyone encounter such a problem? Ideas?

Thanks in advance,

Sam

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