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

Arnd Bergmann
2016-04-27T18:09:06Z

On Wednesday 27 April 2016 13:59:13 Alan Stern wrote:
> On Wed, 27 Apr 2016, Arnd Bergmann wrote:
>
> > I've looked at the usb HCD code now and see this:
> >
> > struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver,
> > struct device *dev, const char *bus_name,
> > struct usb_hcd *primary_hcd)
> > {
> > ...
> > hcd->self.controller = dev;
> > hcd->self.uses_dma = (dev->dma_mask != NULL);
> > ...
> > }
> >
> > What I think we need to do here is ensure that the device that gets
> > passed here and assigned to hcd->self.controller is the actual DMA
> > master device, i.e. the pci_device or platform_device that was created
> > from outside of the xhci stack. This is after all the pointer that
> > gets passed into all the dma_map_*/dma_sync_*/dma_alloc_*/...
> > functions.
>
> It would be better to add a new field, since self.controller is also
> used for lots of other purposes. Something like hcd->self.dma_dev.
>

Ok, fair enough. I only took a brief look and all uses I found were
either for the DMA mapping API or some printk logging.

Arnd