Re: Nokia N900: musb is in wrong state after boot

From: joerg Reisenweber
Date: Thu Jan 21 2016 - 05:57:31 EST

On Thu 21 January 2016 09:40:07 Pali Rohár wrote:
> On Tuesday 19 January 2016 12:33:15 Tony Lindgren wrote:
> > Hi,
> >
> > * Pali Rohár <pali.rohar@xxxxxxxxx> [160109 07:16]:
> > > Hello,
> > >
> > > when I boot 4.4.0-rc7+ kernel compiled with g_nokia into zImage on Nokia
> > > N900 into userspace then usb gadget (g_nokia) does not work. Notebook,
> > > connected on other side does not see any usb device... Connecting and
> > > disconnecting cable does not change anything, still not work.
> > >
> > > But if I run this command
> > > $ echo peripheral > /sys/bus/platform/devices/
> > >
> > >
> > > then gadget starts working. Other side see usb device and can use it.
> > > Also connecting and disconnecting usb cable working fine. After
> > > connecting it again, usb device OK.
> >
> > N900 had the PHY interrupt wired to the bq chip instead of twl4030, right?

which interrupt? I'll try to answer based on assumptions: 1707 PHY connects to
bq24150 charger via CHRG_DET signal.
I guess you're talking about the VBUS detection which is done in twl4030 VBUS-
pin R8.

> I do not know now. I tried to find it in N900 schemantics, but do not
> see it.
> CCing Joerg, do you know?
> > You can fix this issue similar to phy-twl4030-usb.c. In function
> > twl4030_phy_power_on() we call schedule_delayed_work() that checks
> > the state of the ID pin on boot up.
> I looked at that code, but do not see what and how can be fixed :-(
> > I think that's only needed for the i2c based PHY's with MUSB, with
> > the others the USB driver has a better idea of the current state.
> >
> > Regards,
> >
> > Tony

N900 PHY (1707) is connected to musb core via ULPI
(, it has no
I2C interface and no other IRQ than what's implemented in (normally powered-
down?) ULPI already.
I guess the problem in this case is along the USB VBUS and ID pin A/B OTG
detection: the USB jack's ID pin is _not_ connected to the PHY in N900 but
rather is connected to TWL4030 aka GAIA ID pin R11 which afaik is part of the
otherwise unused (except VBUS detection?) PHY in TWL4030.
It seems to me the actually used PHY 1707 does not support ID, neither does it
support a dedicated IRQ line for VBUS.

Generally musb-core and buses should be suspended/off by default, for energy
conservation reasons (seemingly ~40mA on Vbatt!), and only get enabled when
twl4030 detects +5V on VBUS (also before my hostmode botch tries to talk to
the musb core debug registers which needs to happen before VBUS gets applied)

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