Re: [PATCH v3 2/2] usb:dwc3: pass arch data to xhci-hcd child

[santosh shilimkar]

On 4/3/2016 11:28 PM, Felipe Balbi wrote:
> santosh shilimkar <santosh.shilimkar@xxxxxxxxxx> writes:
> > +Arnd, RMK,
> >
> > On 4/1/2016 4:57 AM, Felipe Balbi wrote:
> > > Hi,
> > >
> > > Grygorii Strashko <grygorii.strashko@xxxxxx> writes:
> > > > On 04/01/2016 01:20 PM, Felipe Balbi wrote:
> >
> > [...]
> >
> > > > commit 7ace8fc8219e4cbbfd5b4790390d9a01a2541cdf
> > > > Author: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> > > > Date:   Mon Jul 13 18:10:05 2015 +0900
> > > >
> > > >       usb: gadget: udc: core: Fix argument of dma_map_single for IOMMU
> > > >
> > > >       The dma_map_single and dma_unmap_single should set "gadget->dev.parent"
> > > >       instead of "&gadget->dev" in the first argument because the parent has
> > > >       a udc controller's device pointer.
> > > >       Otherwise, iommu functions are not called in ARM environment.
> > > >
> > > >       Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> > > >       Signed-off-by: Felipe Balbi <balbi@xxxxxx>
> > > >
> > > > Above actually means that DMA configuration code can be dropped from
> > > > usb_add_gadget_udc_release() completely. Right?:
> > >
> > > true, but now I'm not sure what's better: copy all necessary bits from
> > > parent or just pass the parent device to all DMA API.
> > >
> > > Anybody to shed a light here ?
> > The expectation is drivers should pass the proper dev pointers and let
> > core DMA code deal with it since it knows the per device dma properties.
>
> okay, so how do you get proper DMA pointers with something like this:
>
> 	kdwc3_dma_mask = dma_get_mask(dev);
> 	dev->dma_mask = &kdwc3_dma_mask;
>
> This doesn't anything.
Drivers actually needs to touch dma_mask(s) only if the core DMA
code hasn't populated it it. I see Grygorii pointed out couple
of things already.

Reagrds,
Santosh