From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: akepner@sgi.com
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>,
Andrew Morton <akpm@linux-foundation.org>,
grundler@parisc-linux.org, jbarnes@virtuousgeek.org, jes@sgi.com,
randy.dunlap@oracle.com, rdreier@cisco.com,
James.Bottomley@steeleye.com, davem@davemloft.net,
linux-kernel@vger.kernel.org
Subject: Re: [RFC] dma: passing "attributes" to dma_map_* routines
Date: Sat, 22 Dec 2007 08:31:30 +1100 [thread overview]
Message-ID: <1198272690.6737.21.camel@pasglop> (raw)
In-Reply-To: <20071221180022.GW412@sgi.com>
On Fri, 2007-12-21 at 10:00 -0800, akepner@sgi.com wrote:
> On Fri, Dec 21, 2007 at 07:56:25AM +1100, Benjamin Herrenschmidt wrote:
> > ...
> > Can't you just have a primitive to sync things up that you call
> > explicitely from your driver after fetching a new status entry ?
> >
>
> Well, the only mechanisms I know to get things synced are the ones
> I mentioned before: 1) generate an interrupt, 2) write to memory
> which has the "barrier" attribute. Obviously 1 is out - giving
> the memory used for status indications the barrier attribute is
> the most primitive means I'm aware of.
Well, I'm not totally against turning "direction" into a flag mask, as I
do have requests to do something similar on some PowerPC's in fact in
order to control the ordering guarantees of a given DMA mapping (ie.
relaxed vs. fully ordered).
I'm just worried that we'll end up with as many semantics for those
flags as we have host bridges & archs around, which would be bad.
Ben.
prev parent reply other threads:[~2007-12-21 21:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-18 0:17 [RFC] dma: passing "attributes" to dma_map_* routines akepner
2007-12-18 16:50 ` Stefan Richter
2007-12-18 19:04 ` Roland Dreier
2007-12-18 20:07 ` akepner
2007-12-18 20:59 ` Stefan Richter
2007-12-18 21:09 ` Roland Dreier
2007-12-20 18:51 ` akepner
2007-12-20 19:06 ` akepner
2007-12-20 20:56 ` Benjamin Herrenschmidt
2007-12-21 18:00 ` akepner
2007-12-21 20:24 ` Stefan Richter
2007-12-21 21:31 ` Benjamin Herrenschmidt [this message]
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