Re: [PATCH v2 0/3] USB: add generic onboard USB HUB driver

Peter Chen
2015-12-17T06:57:58Z

On Wed, Dec 16, 2015 at 09:05:35PM +0100, Maciej S. Szmigiero wrote:
> Hi Fabio,
> Hi Peter,
>
> On 16.12.2015 11:11, Fabio Estevam wrote:
> > Hi Peter,
> >
> > On Wed, Dec 16, 2015 at 2:11 AM, Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org> wrote:
> >
> >> Thanks, Fabio, but I am curious how things like that? The USBOH3 clock
> >> is not opened, the usb driver will hang when it tries to access
> >> registers. If this clock is always on, then, why the system will
> >> hang later?
> >
> > I found the issue with your patch. You missed to add the pinctrl node.
> >
> > With the change below USB is functional in Udoo:
> >
> > --- a/arch/arm/boot/dts/imx6qdl-udoo.dtsi
> > +++ b/arch/arm/boot/dts/imx6qdl-udoo.dtsi
> > @@ -22,6 +22,8 @@
> >
> > usb_hub1 {
> > compatible = "generic-onboard-hub";
> > + pinctrl-names = "default";
> > + pinctrl-0 = <&pinctrl_usbh>;
> > clocks = <&clks IMX6QDL_CLK_CKO>;
> > reset-gpios = <&gpio7 12 GPIO_ACTIVE_LOW>;
> > reset-duration-us = <2>;
> >
>
> Thanks for your work, I didn't notice it previously (sorry).
>
> I can confirm, too that with Peter's patches and the above change
> the USB support works again on my UDOO DualLite board.
>
> However, I noticed that when you have host USB support configured to be
> build as modules then (due to its location under "if USB") it is only
> possible to compile generic onboard USB HUB as module, too.
>
> Then this module would need to be loaded before loading USB support
> (or quickly after it), otherwise USB enumeration would time out after
> few secs and loading it later wouldn't help.

Thanks for testing it, it maybe this hardware limitation.
The USB device should be back to work whenever do hardware reset,
otherwise, this reset is not clean.

>
> Currently, this driver doesn't really need any USB host support and
> is able to be compiled-in successfully regardless of USB host support
> configuration with just small change to Makefile and Kconfig.
>
> However I don't know if it is a design goal to not use USB host support
> or just a current development status, but if it doesn't really need it
> then it would be great if it could be selected to be build-in into kernel
> regardless of host USB support setting.
>

Yes, you are right, this driver is totally unrelated with ANY usb, but
it intends to handle general USB device which needs to have platform
control, and USB device is on the USB bus. Currently, if you are
USB stuff, you must depends of host or gadget support.

For this special hardware, you may have to define module load sequence
for your loadable support, it the current develop stage, maybe it can
be changed in future, I don't know when.

--

Best Regards,
Peter Chen