[U-Boot] [PATCH v4 2/4] USB: host: Add the USB3 host driver

[Sherry Sun]

Hi Jean,

> 
> 
> On 28/08/2019 13:50, Sherry Sun wrote:
> > Hi Jean,
> >
> >> Hi Jean,
> >>
> >>> Hi Marek, Sherry,
> >>>
> >>>
> >>>>>>> we keep the cdns3 node for usb gadget driver, then add a usb
> >>>>>>> host node for
> >>>>>>> xhci-imx8 driver in *-uboot.dtsi. so here is no need to change
> >>>>>>> the host driver
> >>>>>> compatible.
> >>>>>>> But the compatible in gadget driver should be changed later.
> >>>>>> We should try avoiding ABI breaks in DT.
> >>>>> But the cdns3 usb gaget driver and host driver in different uclass
> >>>>> need two
> >>> dt nodes to bind with.
> >>>>> And the compatible of the two node cannot be same.
> >>>>> So for gadget driver, the compatible may use "cdns,usb3-1.0.0",
> >>>>> for host
> >>> driver, the compatible will use "cdns,usb3-1.0.0-host".
> >>>>> What do you think about it?
> >>>> CCing Jean, since I think he did solve similar topic for his platform.
> >>> I've been OOO for a few weeks and didn't look at the whole series.
> >>>
> >>> For this particular issue, the solution I used is to let the wrapper
> >>> do the binding job. The name of the driver to use is hard-coded in
> >>> the
> >> wrapper diver.
> >>> This is done in dwc3_glue_bind().
> >> Thanks for your suggestions.
> >>
> >> So if I want to use the cdns3 usb node as both usb gadget device and
> >> usb host device, do you mean that I should make the cdns3 usb node as
> >> a usb wrapper device, and create two subnodes in it.
> 
> I think we should not change the binding to adapt to out driver but keep the
> bindings that exist in linux and adapt the u-boot driver
> 
> In the version used by our platform, there is a wrapper around the USB:
> 
>      usbss0: cdns_usb at 4104000 {
>          compatible = "ti,j721e-usb";
>          [....]
>          usb0: usb at 6000000 {
>              compatible = "cdns,usb3-1.0.1";
> 
> The driver selection (host or device) could be done by the wrapper when it
> binds its children (same as the dwc3).
> 
> OR
> 
> The "cdns,usb3-1.0.1" could be a dumb driver the role of which would be
> only to bind a new driver (host or device) based on "dr_mode". The binding
> could be done using the same node, it doesn't have to be a subnode.
> 
> 
> Maybe the second solution will be better, as it would work for platforms that
> do not use a wrapper.
> 

I just communicated with Vignesh Raghavendra <vigneshr at ti.com>, and he suggest that I should keep this cdns3 driver under Linux kernel and U-Boot in sync. And show me your downstream code with v10  of Cadence USB3 kernel driver ported to U-Boot. So I decide to follow your way to deal with this issue.

But I want to ask another question: 
The two solutions you gave before both make the usb node with compatible "cdns,usb3-1.0.1" as a definite device (host or gadget) by its dr_mode property. If I want use this usb device works as both host and gadget driver, which means I want to change its status runtime, such as I want to use this usb device to run both fastboot or usb start command, how can we deal with this?  .

Best regards
Sherry sun

> 
> JJ
> 
> >> Then when binding the wrapper node, it will hard-coded the two
> subnodes
> >> to different driver(gadge/host driver) according to the dr_mode property
> in
> >> nodes.
> >>
> > Do you think I understand it right?
> 
> >
> > Best regards
> > Sherry sun
> >
> >> Best regards
> >> Sherry sun
> >>
> >>> JJ
> >>>
> >>>
> >>>
> >>>>>>>>> +	{ }
> >>>>>>>>> +};
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