linux-kernel - Re: [PATCH v12 4/6] usb: dwc3: qcom: Keep power domain on to retain controller status

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Message-ID: <20220408020016.GA26536@hu-pkondeti-hyd.qualcomm.com>
Date:   Fri, 8 Apr 2022 07:30:16 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Matthias Kaehlcke <mka@...omium.org>
CC:     Sandeep Maheswaram <quic_c_sanm@...cinc.com>,
        Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        <devicetree@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_pkondeti@...cinc.com>, <quic_ppratap@...cinc.com>,
        <quic_kriskura@...cinc.com>, <quic_vpulyala@...cinc.com>
Subject: Re: [PATCH v12 4/6] usb: dwc3: qcom: Keep power domain on to retain
 controller status

On Thu, Apr 07, 2022 at 11:01:57AM -0700, Matthias Kaehlcke wrote:
> On Thu, Apr 07, 2022 at 02:15:02PM +0530, Sandeep Maheswaram wrote:
> > Keep the power domain on in order to retain controller status and
> > to support wakeup from devices.
> > 
> > Signed-off-by: Sandeep Maheswaram <quic_c_sanm@...cinc.com>
> > ---
> >  drivers/usb/dwc3/dwc3-qcom.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> > index 9804a19..35087cf 100644
> > --- a/drivers/usb/dwc3/dwc3-qcom.c
> > +++ b/drivers/usb/dwc3/dwc3-qcom.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/of_platform.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/phy/phy.h>
> > +#include <linux/pm_domain.h>
> >  #include <linux/usb/of.h>
> >  #include <linux/reset.h>
> >  #include <linux/iopoll.h>
> > @@ -724,6 +725,7 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
> >  	struct resource		*res, *parent_res = NULL;
> >  	int			ret, i;
> >  	bool			ignore_pipe_clk;
> > +	struct generic_pm_domain *genpd;
> >  
> >  	qcom = devm_kzalloc(&pdev->dev, sizeof(*qcom), GFP_KERNEL);
> >  	if (!qcom)
> > @@ -732,6 +734,8 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
> >  	platform_set_drvdata(pdev, qcom);
> >  	qcom->dev = &pdev->dev;
> >  
> > +	genpd = pd_to_genpd(qcom->dev->pm_domain);
> > +
> >  	if (has_acpi_companion(dev)) {
> >  		qcom->acpi_pdata = acpi_device_get_match_data(dev);
> >  		if (!qcom->acpi_pdata) {
> > @@ -839,6 +843,8 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
> >  	if (ret)
> >  		goto interconnect_exit;
> >  
> > +	genpd->flags |= GENPD_FLAG_ALWAYS_ON;
> 
> Not sure it really matters, but could this be done conditionally based
> on device_can_wakeup() of the dwc3 core device?

+1. Makes sense to me.

> 
> > +
> >  	device_init_wakeup(&pdev->dev, 1);
> 
> Now that the dwc3 core looks at the wakeup-source property it seems
> this driver should enable wakeup only when it is enabled for the
> core.
> 
> Actually I wonder if it would make sense to leave wakeup for dwc3-qcom
> 'officially' disabled, and just make all wakeup related decisions
> based on the wakeup configuration of the dwc3 core (as
> dwc3_qcom_en/disable_interrupts() already do). The separate wakeup
> policies for dwc3 core and dwc3-qcom are confusing and don't seem to
> add any value.

This suggestion makes sense. Do we foresee any issues by not marking
this parent device not wakeup capable? I don't see any.

Thanks,
Pavan