Subject: Re: [PATCH] ucc_geth: Rework the TX logic.

From: Scott Wood <[email-masked]>
Date: Mon, 30 Mar 2009 12:45:17 -0500

Joakim Tjernlund wrote:
> Scott Wood <[email-masked]> wrote on 30/03/2009 19:22:03:
>> Joakim Tjernlund wrote:
>>> gianfar does not seem to use in_/out_ functions for the BDs. Works 
> just
>>> fine that too it seems.
>> It does now that it has explicit barriers in a few places.  Before they
> 
> In 2.6.29 or later?

No, it was earlier.

>> were added, it would sometimes fail under load.  That was due to a 
>> compiler reordering, but CPU reordering was possible as well.
> 
> Does not the CPU skip reordering if the guarded bit is set?

The guarded bit is typically not set for DMA buffers.  ucc_geth is a bit 
different since descriptors are in MURAM which is ioremap()ed -- though 
switching to a cacheable mapping with barriers should be a performance 
improvement.

-Scott