Re: [PATCH v2 1/2] of/pci: add of_pci_dma_configure() update dma configuration

[Murali Karicheri]

On 01/02/2015 03:57 PM, Arnd Bergmann wrote:
> On Friday 02 January 2015 12:20:53 Murali Karicheri wrote:
> > Initially I had the same idea to re-use the existing function
> > of_dma_configure() for this. I wanted to defer this until we have an
> > agreement on the changes required for the subject functionality. My
> > quick review of the code suggestio this would require additional API
> > changes as below. I did a quick test of the changes and it works for
> > Keystone, but need to be reviewed by everyone as I touch the IOMMU
> > functionality here and I don't have a platform with IOMMU. Need test by
> > someone to make sure I don't break anything.
> >
> > Here are the changes required to implement this suggestion.
> >
> > 1. Move the of_dma_configure() to drivers/of/device.c (include the API
> > in of_device.h) and make it global (using proper EXPORT macro).
> > Otherwise, we will have to include of_platform.h in drivers/of/of_pci.c
> > assuming the prototype is defined in of_platform.h which doesn't look
> > appropriate to me. Would require following additional include files in
> > drivers/of/device.c as well.
> >
> > +#include<linux/of_address.h>
> > +#include<linux/of_iommu.h>
> > +#include<linux/dma-mapping.h>
>
> Yes, sounds good.
>
> > 2. drivers/iommu/of_iommu.c. This is needed so that of_iommu_configure()
> > can take confuguration from the root bus DT as you have suggested.
> >
> > -struct iommu_ops *of_iommu_configure(struct device *dev)
> > +struct iommu_ops *of_iommu_configure(struct device *dev, struct
> > device_node *node)
> >    {
> >           struct of_phandle_args iommu_spec;
> >           struct device_node *np;
> > @@ -145,7 +145,7 @@ struct iommu_ops *of_iommu_configure(struct device *dev)
> >            * See the `Notes:' section of
> >            * Documentation/devicetree/bindings/iommu/iommu.txt
> >            */
> > -       while (!of_parse_phandle_with_args(dev->of_node, "iommus",
> > +       while (!of_parse_phandle_with_args(node, "iommus",
> >                                              "#iommu-cells", idx,
> >                                              &iommu_spec)) {
>
> Right.
>
> > 3. drivers/of/of_pci.c. The existing function (added in this patch) will
> > make call to of_dma_configure() as
> >
> > parent_np = of_get_pci_root_bridge_parent(pci_dev);
> > of_dma_configure(dev, parent_np);
>
> With dev =&pci_dev->dev, I assume?

Yes

> > 4. drivers/of/platform.c. Add a wrapper function
> > of_platform_dma_configure() that calls of_dma_configure() as
> > of_dma_configure(dev, dev->of_node). All existing calls converted to
> > this wrapper.
>
> There are only two callers, I don't think we need a wrapper for it,
> just change the calling conventions along with step 2.

Ok. That is what Rob's comment as well.

> > If the above looks good, I can post v3 of the patch with these changes.
>
> With that one minor change, sounds perfect to me. The same can also
> be used by other bus types if we ever need it.
>
> 	Arnd
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--
Murali Karicheri
Linux Kernel, Texas Instruments
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