[Letux-kernel] musb otg/y-cable regressions, OTG support removal

[Andreas Kemnade]

On Mon, 18 Feb 2019 08:53:20 +0100
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi,
> 
> > Am 18.02.2019 um 07:58 schrieb Andreas Kemnade <andreas at kemnade.info>:
> > 
> > Hi,
> > 
> > after quite some searching why b_host mode only works very randomly, I found
> > out that
> > - musb: disable b_host wait timeout for y-cable usage
> >  is missing in >= letux-4.18. Seems to be forgotten in a conflict resolution.  
> 
> Ok. Do you have a reference to the original patch?
> 
> > - and them we have this one
> > commit 0a9134bd733bbb99bd18f5520a488960170271f2
> > Author: Bin Liu <b-liu at ti.com>
> > Date:   Mon May 21 08:42:19 2018 -0500
> > 
> >    usb: musb: disable otg protocol support
> > 
> >    As decided in the discussion [1] we are deleting the otg protocol
> >    support from the musb drivers.
> > 
> >    First this patch disables the flags for enabling the otg protocols. We
> >    will later gradually delete the otg protocol code from the musb drivers.
> > 
> >    [1] https://www.spinics.net/lists/linux-usb/msg167003.html
> > 
> >    Signed-off-by: Bin Liu <b-liu at ti.com>
> >    Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> > 
> > that seems also to influence things.  
> 
> Hm. What are the effects of this? Does it influcence OTG operation on GTA04?
> 
well, it influences operation if something tries to do hnp.
So it about letting the device say:"hey, I would rather be a usb host".
So then you might have a_peripherals and b_hosts.

Well, there are rare devices which actually use that feature. 
But my b_host hacks actually depend on that logic in the kernel.


> Well, we never had a really OTG compatible socket, just the OTG mode.
> 
Well, the socket on gta04 is a usb-miniab socket, isn't it? So it is
a usb-otg socket.  

Regards,
Andreas
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