[U-Boot] tftp not working for larger rootfs image

[Navaneethan P]

Hi All,

I am using Freescale's iMX51 based custom board with NAND flash size of 
128MB. 
My root file system image size happens to be 75MB.
I have DDR RAM of 128MB.
My DDR Start Address is 0x9000_0000. I am trying to load my root file 
system to 0x9080_0000.(8MB after the starting location).
But when i execute the tftp command, it loads some amount after that it 
hangs up.
U-Boot> tftp 0x90800000 rootfs.jffs2

1. How much memory does the u-boot requires? Is 8MB enough?

2. Since I have 128MB of RAM, I should be able to load 120MB of image 
file. Why does it hangs up?

3. I tried to write the byte data to 0x97ff_ffff (the very last location 
of my RAM). It is working
U-Boot > md.b 0x97ffffff 1
97ffffff: 04    .
U-Boot > mm.b 0x97ffffff
97ffffff: 04 ? 32
U-Boot > md.b 0x97ffffff 1
97ffffff: 32    .

Now I tried to write the data to the next locations. I expected it to hang 
up. but it writes. Then i read the starting locations. But the data was 
written to there.
Why these behavior? Is this behavior is correct? Is there anything wrong 
with my DDR Initialization?
U-Boot > mm.b 0x97ffffff
97ffffff: 04 ? 32
98000000: 09 ? 32
98000001: 00 ? 21
98000002: 0c ? 12
98000003: 00 ? 12
98000004: 08 ?
U-Boot > md.b 0x90000000 4
90000000: 32 21 12 12    2!..

A reply would be greatly appreciated.

Thanks in advance.

Thanks & Regards,
Navaneethan P