linux-kernel - Re: [PATCH] usb: chipidea: Fix missing resume call after suspend

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Date:   Tue, 25 Apr 2017 16:14:03 +0800
From:   Peter Chen <peter.chen@....com>
To:     Bernhard Walle <bernhard@...lle.de>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH] usb: chipidea: Fix missing resume call after suspend

On Mon, Apr 24, 2017 at 01:25:21PM +0000, Bernhard Walle wrote:
> Hi,
> 
> > Peter Chen <peter.chen@....com> hat am 24. April 2017 um 05:51 geschrieben:
> > > 
> > The current code logic is:
> > - When the resume is received from host, the ci->dirver->resume is
> > called, and suspended is cleared.
> > - When the reset is received from host, the isr_reset_handler is called,
> > and suspended is cleared by _gadget_stop_activity. Since reset is
> > called, so ci->driver->resume doesn't need to be called.
> 
> My problem is that dump_stack() doesn't show the complete stackframe. What I see from debug messages is that when I plug a cable (after the host has been suspended) then _gadget_stop_activity is executed before udc_irq. 
> 
> My first attempt was to save ci->suspended at the beginning of udc_irq (i.e. before isr_reset_handler is called), but that doesn't work. Even in the beginning of udc_irq ci->suspended is 0. So isr_reset_handler is called before.
> 
> The result is that when I unplug a cable and attach it again, driver->suspended has been called but driver->resume doesn't get called.
> 
> > There is a patch to fix clear suspended even the ci->driver->resume is
> > NULL at v4.12-rc1.
> > 
> >       usb: chipidea: udc: update gadget state after bus resume
> 
> Thanks for the hint. That makes the second part of my patch irrelevant, but the first part (removing the ci->suspended = 0) is needed in order to make my setup working.
> 
> Any idea to find the cause why reset is called before resume? According to your explanation, that shouldn't be the case?
> 

Since you unplug the cable first, and plug in again. The driver will
treat it as connection but not resume event. You may use 
/sys/class/udc/ci_hdrc.0/state to get udc's connection, eg "not attached"
or other states to indicate connection.

-- 

Best Regards,
Peter Chen