linux-kernel - Re: Nokia N900: musb is in wrong state after boot

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Message-ID: <87oab9nn0i.fsf@ti.com>
Date:	Mon, 22 Feb 2016 10:54:21 +0200
From:	Felipe Balbi <balbi@...nel.org>
To:	Pali Rohár <pali.rohar@...il.com>, b-liu@...com
Cc:	Tony Lindgren <tony@...mide.com>,
	joerg Reisenweber <joerg@...nmoko.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	Sebastian Reichel <sre@...nel.org>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Pavel Machek <pavel@....cz>, Nishanth Menon <nm@...com>
Subject: Re: Nokia N900: musb is in wrong state after boot


Hi,

Pali Rohár <pali.rohar@...il.com> writes:
> On Monday 22 February 2016 09:31:50 Felipe Balbi wrote:
>> Pali Rohár <pali.rohar@...il.com> writes:
>> 
>> > On Tuesday 26 January 2016 18:26:32 Tony Lindgren wrote:
>> >> * Pali Rohár <pali.rohar@...il.com> [160126 06:35]:
>> >> > On Thursday 21 January 2016 12:30:13 Tony Lindgren wrote:
>> >> > > * joerg Reisenweber <joerg@...nmoko.org> [160121 11:35]:
>> >> > > > On Thu 21 January 2016 11:21:13 Tony Lindgren wrote:
>> >> > > > > Do you have some pointer
>> >> > > > > to the "certain resistor value on ID to GND" spec? Is it
>> >> > > > > maybe part of the carkit related parts of the USB spec?
>> >> > > > 
>> >> > > > ""Three additional ID pin states are defined[4] at the nominal
>> >> > > > resistance values of 124 kΩ, 68 kΩ, and 36.5 kΩ, with respect
>> >> > > > to the ground pin. These permit the device to work with USB
>> >> > > > Accessory Charger Adapters that allows the OTG device to be
>> >> > > > attached to both a charger and another device simultaneously.
>> >> > > > [6]""
>> >> > > > https://en.wikipedia.org/wiki/USB_On-The-Go#OTG_micro_plugs
>> >> > > 
>> >> > > OK thanks. So it's the "accessory charger" part of the
>> >> > > battery charging specification 1.1.
>> >> > 
>> >> > So, Tony, do you have some idea what needs to be changed and how to
>> >> > fix peripheral mode after boot on Nokia N900?
>> >> 
>> >> No, I'm waiting to hear an educated guess from Felipe on this one.
>> 
>> about why peripheral mode doesn't work on n900 ? No idea. that's always
>> the default role of MUSB and last I checked, before stopping working on
>> this, BBB was working just fine.
>> 
>> N900 is odd in that it has two PHYs (1701 handles data lines while
>> twl4030 handles power lines, IIRC), but peripheral should be working.
>> 
>> The only reason for MUSB to not start would be that it's not detecting
>> VBUS being above session valid threshold, however twl4030 should have an
>> IRQ for that.
>> 
>> What happens when cable is attached ? Any IRQs anywhere firing ?
>> 
>
> Just to note, when I call echo peripheral > mode then detecting usb
> cable starts working and usb peripheral mode also works fine (also
> after disconnecting and connecting usb cable again). Read my first
> post in this thread, there are also some logs:
> https://lkml.org/lkml/2016/1/9/69

interesting... that softconnect interface looks odd. We _know_ the value
of softconnect from musb->softconnect. /me reads commit which added
it... Oh okay, that's only valid for host mode. Argh!

Okay, the session bit is _NOT_ set when it should be. Note that DevCtl
reads as 0x98. Bit 0 is Session bit and that's not set. MUSB _is_ in the
device mode (bit 7 set).

For some reason DevCtl didn't get set. Care to add a print to
musb_gadget_pullup() to see when/if it's called ?

BTW, Bin will be maintaining MUSB going forward.

-- 
balbi

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