[U-Boot] [PATCH 1/2] integratorap: disable dcache

[Laurence Withers <lwithers@guralp.com>]

On Fri, Jul 15, 2011 at 09:42:53AM +0200, Heiko Schocher wrote:
> Hmm.. trying bootm with actual u-boot on a davinci (arm926ejs) based
> board, there I couldn;t use the Davinci-EMAC (if I disable the dcache
> it works ...)

I can confirm there are some cache coherency problems with the DaVinci EMAC
driver. I've done a port to a new board based on the DA850 and had problems
with corrupt Ethernet packets until I disabled the dcache altogether. The
clue was the packets started working when I added a hex dump just before
eth_send()!

While I haven't come across any explicit documentation I presume the EMAC
controller's independent DMA engine is simply not aware of the ARM's cache.

I haven't yet identified whether there's some mechanism already in U-Boot for
marking particular bits of memory as uncacheable, which would seem to be the
correct approach, but turning of dcache doesn't really have any side effects
that cause problems for me.

Bye for now,
-- 
Laurence Withers, <lwithers@guralp.com>                http://www.guralp.com/
Direct tel:+447753988197 or tel:+443333408643               Software Engineer
General support queries: <support@guralp.com>         CMG-DCM CMG-EAM CMG-NAM