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]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1198272690.6737.21.camel@pasglop \
--to=benh@kernel.crashing.org \
--cc=James.Bottomley@steeleye.com \
--cc=akepner@sgi.com \
--cc=akpm@linux-foundation.org \
--cc=davem@davemloft.net \
--cc=grundler@parisc-linux.org \
--cc=jbarnes@virtuousgeek.org \
--cc=jes@sgi.com \
--cc=linux-kernel@vger.kernel.org \
--cc=randy.dunlap@oracle.com \
--cc=rdreier@cisco.com \
--cc=stefanr@s5r6.in-berlin.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.