[U-Boot] i.MX51: FEC: Cache coherency problem?

[David Jander]

Hi Stefano,

On Mon, 18 Jul 2011 18:55:05 +0200
Stefano Babic <sbabic at denx.de> wrote:

> On 07/18/2011 05:18 PM, David Jander wrote:
> > 
> > Hi all,
> 
> Hi David,
> 
> > What is going on here? Why did this work with caches enabled before??
> 
> I think cache was always disabled..

I had even L2-caches enabled in u-boot (copied/adapted some code from OMAP
cache.S), and called i/dcache_enable() from board code like this:

int board_late_init(void)
{
        power_init();
        probe_board_type();
        icache_enable();
        dcache_enable();

        return 0;
}

Is there a reason this wouldn't have worked before?

Suppose it didn't. Does that mean we need to use the MMU to properly mark
regions of register space and specially FEC BD's as not-cached? Or do we need
to flash caches manually each time such a memory region is accessed?
I am kind of a CPU-speed-junkie, so I am not sure I want to live without
caches enabled in u-boot ;-)

Best regards,

-- 
David Jander
Protonic Holland.