[PATCH 1/2] ARM: dts: sun9i: cubieboard4: Enable USB support

[maxime.ripard@free-electrons.com (Maxime Ripard)]

On Mon, May 11, 2015 at 04:26:58PM +0800, Chen-Yu Tsai wrote:
> >> >> +&usbphy1 {
> >> >> +     phy-supply = <&reg_usb1_vbus>;
> >> >> +     status = "okay";
> >> >> +};
> >> >> +
> >> >> +/*
> >> >> + * Unfortunately reg_usb1_vbus also powers one of the ports from usb3's hub.
> >> >> + * One should always make sure both regulators are enabled and working for
> >> >> + * all USB ports to have power.
> >> >> + */
> >> >
> >> > Can't we just provide the two regulators, and enable both of them so
> >> > that we know that we always have the needed regulators enabled,
> >> > disregarding which USB port is used?
> >>
> >> Would setting "always-on" for both regulators work for you?
> >> Or maybe just the one that's used by both USB hosts?
> >
> > I was more thinking of giving to the phy an additional regulator, so
> > that it would enable both the regulators needed to power up all ports.
> 
> That would require adding back all the regulator-related code I
> removed from the phy driver before it was merged. (sigh) It's not
> like the regulator bindings takes a list.

Yeah, but maybe we can just add an optional device-supply property or
something like that to power up the devices connected on the bus.

> I see this as more of a hardware design flaw, and we should label
> it as such.

This can be seen as one, and we can debate it for some time I guess,
but if the hardware guys were not making crazy stuff like that, we
would run out of work pretty quickly :)

What we really need to do is find a proper and reliable way to handle
this case. Whether we declare it as a flaw or not is a separate
debate.

> And it might still work for self-powered devices even if VBUS is
> off. The USB hub chip is always on.

That still leaves a significant amount of devices out and non
functional, especially very standard devices like USB keys, keyboards
or headsets that you would expect to just work.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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