linux-kernel - Re: [PATCH v2 1/2] of/pci: add of_pci_dma

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Date:	Fri, 02 Jan 2015 21:57:11 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Murali Karicheri <m-karicheri2@...com>
Cc:	Rob Herring <robherring2@...il.com>,
	Will Deacon <will.deacon@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] of/pci: add of_pci_dma_configure() update dma configuration

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?

> 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.

> 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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