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u-boot TFTP cannot download kernel

What I try to run the 'netboot' command in u-boot, it cannot load the kernel image via tftp

Problem Description

u-boot is unable to load the kernel image via tftp. For example:

TFTP from server 192.168.1.23; our IP address is 192.168.1.91
Filename 'image.ub'
Load address: 0x50002000
Loading: 100BASE-T/FD
T T T T T T T ...
Retry count exceeded; starting again

Background

u-boot uses the TFTP (trivial FTP) protocol to load software images via the network. If u-boot cannot successfully connect to your PC as a TFTP server, it will behave in this way.

Workaround

There are a number of possible causes and solutions for this fix.

1. Confirm that your PetaLinux development workstation has a correctly installed and configured TFTP server running. This step is described in the PetaLinux SDK Installation Guide.

2. Confirm that the TFTP port is not blocked by any local firewall installation or settings. Please contact your system administrator to confirm this - PetaLogix cannot advise you on network setup or security topics.

3. If your MicroBlaze or PPC440 system uses the Xilinx ethernetlite IP core (AXI or PLB), ensure that the board is connected to a 100Mbit network link. The ethernetlite IP is unable to negotiate a gigabit link, even if the board level PHY can do so.