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Date: Fri, 26 Mar 2021 13:05:26 +0100
From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH] usb: gadget: aspeed: set port_dev dma mask
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Cc: Sasha Levin <sashal@kernel.org>, Felipe Balbi <balbi@kernel.org>,
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On Fri, Mar 26, 2021 at 12:03:03PM +0000, Robin Murphy wrote:
> This might happen to work out, but is far from correct. Just wait until you 
> try it on a platform where the USB controller is behind an IOMMU...
>
> It looks like something is more fundamentally wrong here - the device 
> passed to DMA API calls must be the actual hardware device performing the 
> DMA, which in USB-land I believe means the controller's sysdev.

The shiny new usb_intf_get_dma_device API provides the device to use.