From mboxrd@z Thu Jan  1 00:00:00 1970
From: Adhiraj <adhiraj@linsyssoft.com>
Date: Wed, 27 Sep 2006 05:20:13 +0000
Subject: Re: __get_free_pages() problem on ia64
Message-Id: <1159333693.3422.3.camel@triumph>
List-Id: <linux-ia64.vger.kernel.org>
References: <1159283801.4407.16.camel@triumph>
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To: linux-ia64@vger.kernel.org

On Tue, 2006-09-26 at 10:48 -0600, Matthew Wilcox wrote:
> On Tue, Sep 26, 2006 at 08:46:40PM +0530, Adhiraj wrote:
> > I found a strange thing on ia64 platform. When I allocate pages using
> > __get_free_pages() with GFP_DMA, sometimes the physical addresses of
> > allocated pages fall beyond 4G.
> > 
> > I am working on a device driver where the device does not support
> > addresses above 4G and hence I have to implement bounce buffers. The
> 
> You should be using the services described in
> Documentation/DMA-mapping.txt rather than allocating your own bounce
> buffers.
Ok, thanks, I will look into it. But the question is why do I get
addresses beyond 4G (virt_to_phys() of returned addresses) even when I
use GFP_DMA. Is this a known problem on ia64?

> 
> > The dma mask for the driver is set to 64 bits using pci_set_dma_mask().
> 
> Well, that's one of your problems right there .... if your device can
> only DMA up to 4GB then you should set it to DMA_32BIT_MASK.
> 
>