linux-kernel - Re: usb: musb: "(null)" in sysfs mode file after disabling a gadget (and at other times, system hangs)

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Message-ID: <20180305192844.GE14921@uda0271908>
Date:   Mon, 5 Mar 2018 13:28:44 -0600
From:   Bin Liu <b-liu@...com>
To:     Pali Rohár <pali.rohar@...il.com>
CC:     Merlijn Wajer <merlijn@...zup.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        <linux-omap@...r.kernel.org>
Subject: Re: usb: musb: "(null)" in sysfs mode file after disabling a gadget
 (and at other times, system hangs)

Merlijn,

On Fri, Mar 02, 2018 at 05:54:39PM +0100, Pali Rohár wrote:
> On Friday 02 March 2018 17:47:52 Merlijn Wajer wrote:
> > >> I would expect it to state "b_idle" instead of "(null)".
> > > 
> > > Actually, I'd like to see (null) whenever a gadget driver is not loaded,
> > > which indicates a gadget is not bound to the udc.
> > 
> > Hm... Sounds fine to me. I'm using this mode in combination with the usb
> > phy (vbus property) to detect if the phone is detect to a 'dumb' charger
> > of a PC, but I can just always have a gadget loaded -- same as before,
> > really.
> 
> For detection if wallcharger or pc usb charger is connected, there is
> isp1704_charger driver. It uses some standard ULPI interface. It reports
> current_max and type (DCP - dedicated, CDP or just usb).

The musb udc driver sets the state to b_idle without checking a
gadget driver, this should be cleaned up. I have add this in my backlog.
But if this issue doesn't bother you much right now, I will make the
action low priority and address it later whenever I got time. (likely
not very soon, I have a hand full of musb driver bugs to fix...)

Regards,
-Bin.