Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev

Felipe Balbi
2016-09-07T10:48:00Z

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Hi,

Robin Murphy <robin.murphy@arm.com> writes:
> On 07/09/16 10:55, Peter Chen wrote:
> [...]
>>> Regarding the DMA configuration that you mention in ci_hdrc_add_device(),
>>> I think we should replace
>>>
>>> pdev->dev.dma_mask = dev->dma_mask;
>>> pdev->dev.dma_parms = dev->dma_parms;
>>> dma_set_coherent_mask(&pdev->dev, dev->coherent_dma_mask);
>>>
>>> with of_dma_configure(), which has the chance to configure more than
>>> just those three, as the dma API might look into different aspects:
>>>
>>> - iommu specific configuration
>>> - cache coherency information
>>> - bus type
>>> - dma offset
>>> - dma_map_ops pointer
>>>
>>> We try to handle everything in of_dma_configure() at configuration
>>> time, and that would be the place to add anything else that we might
>>> need in the future.
>>>
>>
>> Yes, I agree with you, but just like Felipe mentioned, we also need to
>> consider PCI device, can we do something like gpiod_get_index does? Are
>> there any similar APIs like of_dma_configure for ACPI?
>
> Not yet, but Lorenzo has one in progress[1], primarily for the sake of
> abstracting away the IOMMU configuration.
>
> Robin.
>
> [1]:http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1209911.html

not exported for drivers to use. If Lorenzo is trying to making a
matching API for ACPI systems, then it needs to follow what
of_dma_configure() is doing, and add an EXPORT_SYMBOL_GPL()

--
balbi

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