Re: droid4 -- weird behaviour when attempting to use usb host

Unknown
2023-09-27T17:06:22Z

On Wed, 2023-09-27 at 17:52 +0200, Pavel Machek wrote:
> Hi!
>
> > > I'm having some fun with usb host. Good news is it works with
> > > externally powered hub... after a while. I get some error
> > > messages
> > > about inability to go host mode, but with enough patience it
> > > eventually does enter host mode and I see my keyboard/mouse.
> > >
> > > And usually in that process, one of my cpu cores disappear. top
> > > no
> > > longer shows 2 cores, and I was wondering for a while if d4 is
> > > single-core system. It is not, my two cores are back after
> > > reboot.
> > >
> > > That's with 6.1.9 kernel from leste. Ideas how to debug this
> > > would be
> > > welcome. (Do you use usb host?)
> >
> > You are using a "proper" non-standard usb micro-b cable that
> > grounds
> > the id pin, right?
>
> Yes.
>
> > If not, try with one of those as it allows the hardware to do what
> > it's
> > supposed to do.
> >
> > And presumably you don't have a hacked usb hub that feeds back the
> > vbus to your phone, right?
>
> Do have hacked hub. Or more precisely, have device that needs
> external
> power (spinning rust), and hub passes it back to the device.
>
> I'll retry with a keyboard... but I recall it behaved funny with
> that, too.
>
> > If you have, that should not be used as the pmic can feed vbus.
>
> Well, my plan was to use it as a desktop, and external power is
> useful
> that as Droid battery is not that big.
>
> Best regards,
>                                                                 Pavel

I use usb host quite a bit with xt875, mostly to have a keyboard.
I have noted that several hubs i have don't work reliably, im not sure
why. Its possible that they use or request too mutch power from the
port as cpcap has a pretty small vbus out limit.

All my regular otg adapters work fine however.

I also have a powered hub that works quite well, its item 373697032160
on ebay