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

Robin Murphy
2016-09-07T10:33:13Z

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