linux-kernel - Re: [PATCH v2 3/9] usb: dwc3: qcom: fix gadget-only builds

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Date:   Thu, 18 Aug 2022 19:44:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Felipe Balbi <balbi@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Krishna Kurapati <quic_kriskura@...cinc.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Pavankumar Kondeti <quic_pkondeti@...cinc.com>,
        quic_ppratap@...cinc.com, quic_vpulyala@...cinc.com,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v2 3/9] usb: dwc3: qcom: fix gadget-only builds

On Mon, Aug 08, 2022 at 03:34:10PM +0200, Johan Hovold wrote:
> On Mon, Aug 08, 2022 at 03:05:36PM +0200, Greg Kroah-Hartman wrote:
> > On Thu, Aug 04, 2022 at 05:09:55PM +0200, Johan Hovold wrote:
> > > A recent change added a dependency to the USB host stack and broke
> > > gadget-only builds of the driver.
> > > 
> > > Fixes: 6895ea55c385 ("usb: dwc3: qcom: Configure wakeup interrupts during suspend")
> > > Reported-by: Randy Dunlap <rdunlap@...radead.org>
> > > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> > > ---
> > > 
> > > Changes in v2
> > >  - new patch
> > > 
> > >  drivers/usb/dwc3/dwc3-qcom.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> > > index be2e3dd36440..e9364141661b 100644
> > > --- a/drivers/usb/dwc3/dwc3-qcom.c
> > > +++ b/drivers/usb/dwc3/dwc3-qcom.c
> > > @@ -310,8 +310,11 @@ static enum usb_device_speed dwc3_qcom_read_usb2_speed(struct dwc3_qcom *qcom)
> > >  	 * currently supports only 1 port per controller. So
> > >  	 * this is sufficient.
> > >  	 */
> > > +#ifdef CONFIG_USB
> > >  	udev = usb_hub_find_child(hcd->self.root_hub, 1);
> > 
> > If a gadget driver needs this for some reason, then the #ifdef should be
> > put in a .h file, not in a .c file.
> 
> Yeah, if we're keeping this long-term then yes, and possibly also
> otherwise.
> 
> > But step back a minute and ask why a host-config-only function is being
> > called when a device is in gadget-only mode?  This feels like a
> > design/logic issue in this file, NOT something to paper over with a
> > #ifdef in a .c file
> 
> We're not as I'm fixing that bug in later in the series. I should
> probably have put this one after that fix, but figured fixing the build
> was more important than a harder-to-hit NULL-deref due to non-host mode
> not being considered when the offending series was merged.
> 
> > This implies that if this device is NOT in a host configuration, then
> > the suspend path of it is not configured properly at all, as why would
> > it be checking or caring about this at all if this is in gadget-only
> > mode?
> 
> Right, so see path 6/9 which addresses this by only calling this hack
> when in host mode:
> 
> 	https://lore.kernel.org/all/20220804151001.23612-7-johan+linaro@kernel.org/
> 
> > Something else is wrong here, let's fix the root problem please.  Maybe
> > this driver should just never be built in gadget-only mode, as it is
> > never intended to support that option?
> 
> The problem is commit 6895ea55c385 ("usb: dwc3: qcom: Configure wakeup
> interrupts during suspend"), which I considered simply reverting but as
> that breaks suspend completely on some boards I decided to try and fix
> it up while we work on a proper long-term solution (i.e. for how the
> dwc/xhci layers should be communicating to implement this).
> 
> Remember that it took two years and 21 revisions to get to the state
> we're at now after you merged the wakeup series in June.

Very good point.  This is a mess, thanks for cleaning it up.  I've
applied this series now and will get it into 6.0-final, hopefully all
should be good now.

thanks for doing this work.

greg k-h