From: "Luck, Tony" <tony.luck@intel.com>
To: John Keller <jpk@sgi.com>, Bernhard Walle <bwalle@suse.de>
CC: "linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Date: Tue, 18 Nov 2008 07:35:15 -0800
Subject: RE: [PATCH] ia64: SN specific version of dma_get_required_mask()
Thread-Topic: [PATCH] ia64: SN specific version of dma_get_required_mask()
Thread-Index: AclJhz3mfhqW0t1hR5S8NvpIdhemOQACyGIA
Message-ID: <57C9024A16AD2D4C97DC78E552063EA35C454266@orsmsx505.amr.corp.intel.com>
References: <20081117173930.35342b31@hale.suse.de> from "Bernhard Walle" at
 Nov 17, 2008 05:39:30 PM
 <200811181408.mAIE8BHH057134@fcbayern.americas.sgi.com>
In-Reply-To: <200811181408.mAIE8BHH057134@fcbayern.americas.sgi.com>
Accept-Language: en-US
Content-Language: en-US
acceptlanguage: en-US
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 8BIT
MIME-Version: 1.0
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 837
Lines: 18

> This patch addresses a problem on SN Altix systems with < 4GB, where
> device drivers using the dma_get_required_mask() API would be told
> to use 32 bit DMA, when 64 bit is more efficient.

Even if someone did configure an Altix with < 4GB (which seems a very
unlikely occurance) all of that 4G would be located above 4GB (lowest
physical address on Altix is something like 384 TB, isn't it?)

Did we really make some dma mask decisions based on the amount
of memory rather than its location?  If we do, then perhaps we
should fix this in a generic place, not in sn2 specific code.

-Tony
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/