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Message-ID: <994d5d7187a96fa48ade9244bcc9bd57465bf487.camel@uvos.xyz>
Subject: Re: droid4 -- weird behaviour when attempting to use usb host
From:   Unknown <devnull@uvos.xyz>
To:     Pavel Machek <pavel@ucw.cz>, Tony Lindgren <tony@atomide.com>
Cc:     kernel list <linux-kernel@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-omap@vger.kernel.org, sre@kernel.org, nekit1000@gmail.com,
        mpartap@gmx.net, merlijn@wizzup.org, martin_rysavy@centrum.cz,
        phone-devel@vger.kernel.org, maemo-leste@lists.dyne.org
Date:   Wed, 27 Sep 2023 18:50:26 +0200
In-Reply-To: <ZRRPsWQiTP21hozK@duo.ucw.cz>
References: <ZRGa+0OFNluV4T5t@localhost> <20230926071415.GW5285@atomide.com>
         <ZRRPsWQiTP21hozK@duo.ucw.cz>
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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