From: Clemens Ladisch <clemens@ladisch.de>
To: Peter Hurley <peter@hurleysoftware.com>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>,
linux1394-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] firewire: Enable physical DMA above 4GB
Date: Tue, 26 Mar 2013 17:12:58 +0100 [thread overview]
Message-ID: <5151C90A.5010108@ladisch.de> (raw)
In-Reply-To: <1364307734-27709-1-git-send-email-peter@hurleysoftware.com>
Peter Hurley wrote:
> Quadlet reads to memory above 4GB is painfully slow when serviced
> by the AR DMA context. In addition, the CPU(s) may be locked-up,
> preventing any transfer at all.
Using physical DMA prevents the use of that address space for software
address handlers, so you have adjust the low_memory_region start in
core-transaction.c.
> Write the PhyUpperBound register with the end-of-memory value. If
> end-of-memory is beyond the OHCI limit of 0x0000ffff00000000,
> clamp to that value.
You will have to lower this limit; there are protcols that assume that
addresses like 0xecc000000000 are available for software.
Regards,
Clemens
next prev parent reply other threads:[~2013-03-26 16:13 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-26 14:22 [PATCH] firewire: Enable physical DMA above 4GB Peter Hurley
2013-03-26 16:12 ` Clemens Ladisch [this message]
2013-03-26 17:04 ` Peter Hurley
2013-03-26 18:22 ` Clemens Ladisch
2013-03-26 18:56 ` Stefan Richter
2013-03-26 19:08 ` Peter Hurley
2013-03-26 20:35 ` Stefan Richter
2013-03-29 10:44 ` Stefan Richter
2013-03-29 10:50 ` Peter Hurley
2013-03-29 11:19 ` Clemens Ladisch
2013-03-29 11:31 ` Peter Hurley
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