linux-kernel - Re: [PATCH] usb: dwc3: gadget: call gadget driver's ->suspend/->resume

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Message-ID: <20150427145558.GA11345@psi-dev26.jf.intel.com>
Date:	Mon, 27 Apr 2015 07:55:58 -0700
From:	David Cohen <david.a.cohen@...ux.intel.com>
To:	Felipe Balbi <balbi@...com>
Cc:	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] usb: dwc3: gadget: call gadget driver's
 ->suspend/->resume

On Sat, Apr 25, 2015 at 10:47:42AM -0500, Felipe Balbi wrote:
> Hi,

Hi Felipe,

> 
> On Fri, Apr 24, 2015 at 01:56:25PM -0700, David Cohen wrote:
> > > > > > When going into bus suspend/resume we _must_
> > > > > > call gadget driver's ->suspend/->resume callbacks
> > > > > > accordingly. This patch implements that very feature
> > > > > > which has been missing forever.
> > > > > > 
> > > > > > Cc: <stable@...r.kernel.org> # 3.14
> > > > > > Signed-off-by: Felipe Balbi <balbi@...com>
> > > > > > Signed-off-by: David Cohen <david.a.cohen@...ux.intel.com>
> > > > > > ---
> > > > > > 
> > > > > > Hi,
> > > > > > 
> > > > > > This patch was introduced on v3.15.
> > > > > > But the issue it fixes already existed on v3.14 and v3.14 is a long term
> > > > > > support version.
> > > > > 
> > > > > Can you show me a log of this breaking anywhere ? Why do you consider
> > > > > this a bug fix ? What sort of drawbacks did you notice ?
> > > > 
> > > > We're seeing BC1.2 compliance test failure. I borrowed this info from
> > > > the bug report :)
> > > > 
> > > > 1. BC1.2 compliance testing - SDP2.0
> > > > -----------------------------------------------
> > > > 1. On Connect to active Host (Expected result: 100mA to 500mA):
> > > >    Actual result 100mA to 500mA
> > > > 
> > > > 2. On Host Suspend (ER: Fall back to 0mA):
> > > >    not falling back to 0mA, remains at 500mA
> > > > 
> > > > 3. On Connect to Suspended Host (ER: 100mA to 0mA):
> > > >    cable-props shown as 100mA, which means drawing a current of 100mA from
> > > >    Suspended Host
> > > > 
> > > > 4. On making Host active (ER: 500mA):
> > > >    500mA
> > > 
> > > But we don't support Battery Charging with dwc3 as of now :-) In fact,
> > > just note that none of the BC registers are even defined in the current
> > > driver anywhere. Seems like you should cherry-pick these to your vendor
> > > tree, but v3.14 vanilla, because it doesn't support BC1.2, can't be
> > > claimed to be at fault, right ?
> > 
> > We could call it a missing feature that could lead to a potential bug :)
> > By your own comment, he "must" was stressed out:
> 
> sure it was because they really must be called :-) However, the only
> actual problem that arises from not calling them is with something
> that's not supported :-)
> 
> > When going into bus suspend/resume we _must_
> > call gadget driver's ->suspend/->resume callbacks
> > accordingly. This patch implements that very feature
> > which has been missing forever.
> > '''
> > 
> > Since v3.14 is a LTS kernel and the changes are safe, it's worth to
> > consider.
> 
> definitely worth to consider, but not as something that fixes BC1.2
> because that's, as said, not supported in any public tree :-)

Thanks for the reply.
The gadget having this issue is really out-of-tree (android gadget).
I could do 2 next steps:
1) I could drop android gadget and try to reproduce this issue using
legacy g_ffs, which supports adbd as well.
2) I could propose this change directly on google's android 3.14 tree
instead.

Would you prefer one of those?

Thanks,

David

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