linux-kernel - Re: [PATCH v7 2/4] usb: dwc3: qcom: Add interconnect support in dwc3 driver

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Date:   Mon, 18 May 2020 11:35:12 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Georgi Djakov <georgi.djakov@...aro.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Sandeep Maheswaram <sanm@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Manu Gautam <mgautam@...eaurora.org>,
        Chandana Kishori Chiluveru <cchiluve@...eaurora.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH v7 2/4] usb: dwc3: qcom: Add interconnect support in dwc3
 driver

On Thu 14 May 23:29 PDT 2020, Felipe Balbi wrote:

> 
> Hi,
> 
> Georgi Djakov <georgi.djakov@...aro.org> writes:
> >>>>>> Sandeep Maheswaram <sanm@...eaurora.org> writes:
> >>>>>>> +static int dwc3_qcom_interconnect_init(struct dwc3_qcom *qcom)
> >>>>>>> +{
> >>>>>>> +	struct device *dev = qcom->dev;
> >>>>>>> +	int ret;
> >>>>>>> +
> >>>>>>> +	if (!device_is_bound(&qcom->dwc3->dev))
> >>>>>>> +		return -EPROBE_DEFER;
> >>>>>>
> >>>>>> this breaks allmodconfig. I'm dropping this series from my queue for
> >>>>>> this merge window.
> >>>>>
> >>>>> Sorry, I meant this patch ;-)
> >>>>
> >>>> I guess that's due to INTERCONNECT being a module. There is currently a
> >>>
> >>> I believe it's because of this:
> >>> ERROR: modpost: "device_is_bound" [drivers/usb/dwc3/dwc3-qcom.ko] undefined!
> >>>
> >>>> discussion about this  with Viresh and Georgi in response to another
> >>>> automated build failure. Viresh suggests changing CONFIG_INTERCONNECT
> >>>> from tristate to bool, which seems sensible to me given that interconnect
> >>>> is a core subsystem.
> >>>
> >>> The problem you are talking about would arise when INTERCONNECT=m and
> >>> USB_DWC3_QCOM=y and it definitely exists here and could be triggered with
> >>> randconfig build. So i suggest to squash also the diff below.
> >>>
> >>> Thanks,
> >>> Georgi
> >>>
> >>> ---8<---
> >>> diff --git a/drivers/usb/dwc3/Kconfig b/drivers/usb/dwc3/Kconfig
> >>> index 206caa0ea1c6..6661788b1a76 100644
> >>> --- a/drivers/usb/dwc3/Kconfig
> >>> +++ b/drivers/usb/dwc3/Kconfig
> >>> @@ -129,6 +129,7 @@ config USB_DWC3_QCOM
> >>>  	tristate "Qualcomm Platform"
> >>>  	depends on ARCH_QCOM || COMPILE_TEST
> >>>  	depends on EXTCON || !EXTCON
> >>> +	depends on INTERCONNECT || !INTERCONNECT
> >> 
> >> I would prefer to see a patch adding EXPORT_SYMBOL_GPL() to device_is_bound()
> >
> > Agree, but just to clarify, that these are two separate issues that need to
> > be fixed. The device_is_bound() is the first one and USB_DWC3_QCOM=y combined
> > with INTERCONNECT=m is the second one.
> 
> If INTERCONNECT=m, QCOM3 shouldn't be y. I think the following is
> enough:
> 
> 	depends on INTERCONNECT=y || INTERCONNECT=USB_DWC3_QCOM
> 

This misses the case where INTERCONNECT=n and USB_DWC3_QCOM=[ym] which
I don't see a reason for breaking.

But if only INTERCONNECT where a bool, then we don't need to specify a
depends on, because it will either be there, or the stubs will.
We've come to this conclusion in a lot of different frameworks and I
don't see why we should do this differently with INTERCONNECT.

Regards,
Bjorn