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

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Message-ID: <54A709A5.1000801@ti.com>
Date:	Fri, 2 Jan 2015 16:12:05 -0500
From:	Murali Karicheri <m-karicheri2@...com>
To:	Arnd Bergmann <arnd@...db.de>
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 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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