Atmel Studio / Enabling DCache with LWIP_RAW_BASIC_HTTP_EXAMPLE for SAME70Q21 doesn't work

Hello,

I'm using Atmel Studio together with the SAME70 X PLAINED development 
board.

I'm trying to run example project LWIP_RAW_BASIC_HTTP_EXAMPLE for 
SAME70Q21 with cache enabled:

#define CONF_BOARD_ENABLE_CACHE (in conf_board.h)

As soon as I enable the cache, the HTTP web server included in the 
example project doesn't work anymore, I don't get access.

I put the GMAC Tx/Rx descriptors into nocache memory section

_attribute_ ((section (".ram_nocache"), aligned (32))) static struct 
gmac_device gs_gmac_dev;

but with no success.

Do you have any suggestions how to get the project running with cache 
enabled? I need the cache for my application to speed up data 
processing.