From: "David S. Miller" <davem@redhat.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: olh@suse.de, linux-kernel@vger.kernel.org
Subject: Re: consistent_sync_for_cpu() and friends on ppc32
Date: Tue, 16 Mar 2004 10:46:27 -0800 [thread overview]
Message-ID: <20040316104627.47fc1f25.davem@redhat.com> (raw)
In-Reply-To: <1079400967.2302.213.camel@gaston>
On Tue, 16 Mar 2004 12:36:07 +1100
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> Hrm... I'm still not sure how I'm supposed to implement those
> for non-consistent PPCs (embedded). We don't carry state information
> around, so I suppose I'll have to rely on the direction beeing the
> same for the whole duration of the operation... In which case, it's
> just a matter of having for_cpu nop'ing when direction is TO_DEVICE
> and for_device nop'ing when direction is FROM_DEVICE ? Not clear
> imho...
See, the direction really doesn't matter for the sync ops.
If you flush the cpu caches at MAP time, and your PCI controller doesn't
have DMA caching or something like that, then sync for CPU can always be
a nop. You will have always previously flushed the cpu caches before
giving the buffer back to the device, either via MAP or sync for device
calls.
So basically, make MAP and sync for device writeback flush the cpu caches.
next prev parent reply other threads:[~2004-03-16 18:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-15 20:16 consistent_sync_for_cpu() and friends on ppc32 Olaf Hering
2004-03-15 20:36 ` David S. Miller
2004-03-15 21:59 ` Benjamin Herrenschmidt
2004-03-16 0:23 ` Benjamin Herrenschmidt
2004-03-16 0:49 ` David S. Miller
2004-03-16 1:36 ` Benjamin Herrenschmidt
2004-03-16 18:46 ` David S. Miller [this message]
2004-03-16 21:54 ` Benjamin Herrenschmidt
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