On Fri, 2015-02-27 at 17:16 +0100, Geert Uytterhoeven wrote:

Commit 740c7f31c094703c ("sh_eth: Ensure DMA engines are stopped before
freeing buffers") added a call to sh_eth_reset() to the
sh_eth_set_ringparam() and sh_eth_close() paths.

However, setting the software reset bit(s) in the EDMR register resets
the MAC Address Registers to zero. Hence after kexec, the new kernel
doesn't detect a valid MAC address and assigns a random MAC address,
breaking DHCP.

[...]

Sorry about that.  This would also affect removing and reloading the
driver as a module, but currently I always have it built in and don't
use kexec.

Ben.