Re: __get_free_pages() problem on ia64

[Adhiraj <adhiraj@linsyssoft.com>]

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.
> 
>