Re: [PATCH 1/1] arm/dts: Tegra30: Add device tree support for SMMU

[Thierry Reding <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>]

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* Hiroshi Doyu wrote:
> On Mon, 16 Apr 2012 17:34:19 +0200
> Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
> 
> > On Monday 16 April 2012, Hiroshi Doyu wrote:
> > > What about using "dma-window" property to specify IOVA range in dtsi as below?
> > > 
> > > arch/powerpc/platforms/cell/iommu.c:
> > > 
> > > 698 static int __init cell_iommu_get_window(struct device_node *np,
> > > 699                                          unsigned long *base,
> > > 700                                          unsigned long *size)
> > > 701 {
> > > 702         const void *dma_window;
> > > 703         unsigned long index;
> > > 704
> > > 705         /* Use ibm,dma-window if available, else, hard code ! */
> > > 706         dma_window = of_get_property(np, "ibm,dma-window", NULL);
> > > 707         if (dma_window == NULL) {          ^^^^^^^^^^^^^^
> > > 708                 *base = 0;
> > > 709                 *size = 0x80000000u;
> > > 710                 return -ENODEV;
> > > 711         }
> > > 712
> > > 713         of_parse_dma_window(np, dma_window, &index, base, size);
> > > 714         return 0;
> > > 715 }
> > > 
> > 
> > Yes, that's the right way to do it, but I would use the more generic
> > "dma-window" name rather than "ibm,dma-window", which was originally
> > introduced for pseries and for some reason copied into the cell qs2x
> > firmware.
> 
> Which name is better, "dma-window" or "iova-window"?
> Considering DMA IOMMU mapping API, "dma-window" may sound appropriate to me.

But the window isn't necessarily used for DMA transfers. I was going to
propose "aperture", but that doesn't seem quite right since it is a very
GART-specific term. "iova-window" sounds like the best fit for what it
really is.

Thierry

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