Re: [PATCH] usb: dwc3: be more verbose on ERRATIC_ERROR interrupt

[Felipe Balbi]

On Wed, Oct 15, 2014 at 11:36:33AM -0700, David Cohen wrote:
> On Wed, Oct 15, 2014 at 12:06:10PM -0500, Felipe Balbi wrote:
> > On Wed, Oct 15, 2014 at 10:01:45AM -0700, David Cohen wrote:
> > > On Wed, Oct 15, 2014 at 09:57:18AM -0700, David Cohen wrote:
> > > > On Wed, Oct 15, 2014 at 12:00:22AM -0500, Felipe Balbi wrote:
> > > > > Hi,
> > > > > 
> > > > > On Tue, Oct 14, 2014 at 01:15:05PM -0700, David Cohen wrote:
> > > > > > ERRATIC_ERROR interrupt is an event that needs more attention from
> > > > > > developers than currently implemented, since this indicates a serious
> > > > > > stability issue. The only way to get warned about it is by selecting the
> > > > > > maximum driver's verbosity.
> > > > > > 
> > > > > > This patch increases a bit the error's verbosity.
> > > > > > 
> > > > > > Signed-off-by: David Cohen <david.a.cohen@xxxxxxxxxxxxxxx>
> > > > > > ---
> > > > > >  drivers/usb/dwc3/gadget.c | 3 ++-
> > > > > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > > > > > index 3818b26bfc05..132e761d62e4 100644
> > > > > > --- a/drivers/usb/dwc3/gadget.c
> > > > > > +++ b/drivers/usb/dwc3/gadget.c
> > > > > > @@ -2484,7 +2484,8 @@ static void dwc3_gadget_interrupt(struct dwc3 *dwc,
> > > > > >  		dev_vdbg(dwc->dev, "Start of Periodic Frame\n");
> > > > > >  		break;
> > > > > >  	case DWC3_DEVICE_EVENT_ERRATIC_ERROR:
> > > > > > -		dev_vdbg(dwc->dev, "Erratic Error\n");
> > > > > > +		WARN_ON_ONCE(1);
> > > > > > +		dev_dbg(dwc->dev, "Erratic Error\n");
> > > > > 
> > > > > how about:
> > > > > 		WARN_ONCE(true, "Erratic Error\n");
> > > > > 
> > > > > instead ?
> > > > 
> > > > When erratic error event happens, in my experience it is usually
> > > > followed but many of them in a row. It may end up too verbose.
> > > 
> > > Oops, sorry for my confusion. I read WARN(), not WARN_ONCE() when I read
> > > for the first time :)
> > > 
> > > I let the dev_dbg() because it may be useful to get all the occurrences
> > > in case debug is enabled. But WARN_ONCE() is fine too if you prefer.
> > 
> > We might WARN_ONCE() and forcibly disconnect from host as the platform
> > worn't work anymore after Erratic Error happens. Then just make that
> > clear with "Erratic Error: disconnecting from host\n" or something like
> > that.
> 
> That works.
> I assume calling dwc3_gadget_disconnect_interrupt() from
> DWC3_DEVICE_EVENT_ERRATIC_ERROR should be enough to disconnect the
> gadget and propagate the status to userspace.
> 
> > 
> > The only way to fix erratic error (by fixing code - probably PHY driver)
> > will require rebooting the platform anyway. At a minimum, you'd have to
> > unload and reload dwc3.ko, just make sure (if you can reproduce erratic
> > error easily) modprobe -r dwc3 && modprobe dwc3 still causes dwc3 to
> > reconnect to host.
> 
> It does. Forcing soft reset on whole IP is how databook describes to
> solve it.

alright, then please send a patch and I'll take for v3.19

-- 
balbi

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