[U-Boot] [PATCH v4 2/4] USB: host: Add the USB3 host driver
Sherry Sun
sherry.sun at nxp.com
Sat Aug 31 04:03:32 UTC 2019
Hi Vignesh,
>
>
>
> On 30/08/19 3:36 PM, Sherry Sun wrote:
> > 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? .
> >
>
> AFAIK, U-Boot does not support runtime switching of USB port to host from
> device and vice versa. This is the case for existing driver like DWC3/MUSB etc.
>
> Ideally we would need a role switch driver that unbinds and rebinds host vs
> device driver as when required based on U-Boot cmd or via an API (if
> required to be done during SPL stage etc).
I wonder if we can add two subnodes under the wrapper node as below, one bind to usb gadget driver and another bind to usb host driver.
So if we want to use usb device, just call the gadget driver, and if want to use usb host, just call the host driver. The driver will probe correspond node.
I'm not sure if it is feasible, what do you think about it?
usbss0: cdns_usb at 4104000 {
compatible = "ti,j721e-usb";
[....]
usb0: usb at 6010000 { /* xhci reg address*/
compatible = "cdns,usb3-1.0.1";
dr_mode = "host";
[....]
}
usb1: usb at 6020000 { /* dev reg address*/
compatible = "cdns,usb3-1.0.1";
dr_mode = "peripheral";
[....]
}
}
Best regards
Sherry sun
>
> Regards
> Vignesh
>
> > 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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> --
> Regards
> Vignesh
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