[U-Boot] arm: Activating dcache breaks 'usb start' and 'tftpboot' on jadecpu

["Matthias Weißer" <weisserm@arcor.de>]

Hello Wolfgang

Am 03.12.2010 15:47, schrieb Wolfgang Denk:
>> Has anyone an explanation for this behavior? Is anyone out there having
>> dcache running on an ARM926 and working usb/tftpboot?
>
> Many drivers have not been written to work with enabled caches.

What is the reason that special handling is needed when dcache is 
enabled? If a driver doesn't use any DMA there should be no need as the 
dcache is only enabled for the RAM and not for any memory mapped IO if I 
understand the code in arch/arm/lib/cache-cp15.c right.

> As far as USB is concerned, you might be lucky that your system usies
> a EHCI controller, so setting CONFIG_EHCI_DCACHE should help.

No, only OHCI.

> As for the network driver, you will probably have to figure out
> yourself how to fix that.

As the memory mapped network controller (SMSC9221) is not cached it 
shouldn't be a problem or do I miss something here?

> Patches welcome.

If someone can give me a little push into the right direction I will try 
but currently I have no idea what to do besides activating the cache 
right before the default "bootm" booting.

Thanks a lot
Matthias