linux-kernel - Re: [PATCH v7 5/5] usb: dwc3: qcom: Keep power domain on to support wakeup

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Date:   Thu, 13 May 2021 07:34:33 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Sandeep Maheswaram <sanm@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Manu Gautam <mgautam@...eaurora.org>
Subject: Re: [PATCH v7 5/5] usb: dwc3: qcom: Keep power domain on to support
 wakeup

On Thu, May 13, 2021 at 04:49:19PM +0300, Felipe Balbi wrote:
> 
> Hi,
> 
> Matthias Kaehlcke <mka@...omium.org> writes:
> >> Sandeep Maheswaram <sanm@...eaurora.org> writes:
> >> > If wakeup capable devices are connected to the controller (directly
> >> > or through hubs) at suspend time keep the power domain on in order
> >> > to support wakeup from these devices.
> >> >
> >> > Signed-off-by: Sandeep Maheswaram <sanm@...eaurora.org>
> >> > ---
> >> >  drivers/usb/dwc3/dwc3-qcom.c | 17 +++++++++++++++++
> >> >  1 file changed, 17 insertions(+)
> >> >
> >> > diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> >> > index 82125bc..1e220af 100644
> >> > --- a/drivers/usb/dwc3/dwc3-qcom.c
> >> > +++ b/drivers/usb/dwc3/dwc3-qcom.c
> >> > @@ -17,9 +17,11 @@
> >> >  #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>
> >> > +#include <linux/usb/hcd.h>
> >> >  
> >> >  #include "core.h"
> >> >  
> >> > @@ -354,10 +356,19 @@ static int dwc3_qcom_suspend(struct dwc3_qcom *qcom)
> >> >  {
> >> >  	u32 val;
> >> >  	int i, ret;
> >> > +	struct dwc3 *dwc = platform_get_drvdata(qcom->dwc3);
> >> > +	struct usb_hcd  *hcd;
> >> > +	struct generic_pm_domain *genpd = pd_to_genpd(qcom->dev->pm_domain);
> >> >  
> >> >  	if (qcom->is_suspended)
> >> >  		return 0;
> >> >  
> >> > +	if (dwc->xhci) {
> >> > +		hcd = platform_get_drvdata(dwc->xhci);
> >> > +		if (usb_wakeup_enabled_descendants(hcd->self.root_hub))
> >> > +			genpd->flags |= GENPD_FLAG_ACTIVE_WAKEUP;
> >> > +	}
> >> 
> >> wow, you really need to find a way to do these things generically
> >> instead of bypassing a bunch of layers and access stuff $this doesn't
> >> directly own.
> >>
> >> I'm gonna say 'no' to this, sorry. It looks like xhci should, directly,
> >> learn about much of this instead of hiding it 3-layers deep into the
> >> dwc3 glue layer for your specific SoC.
> >
> > Maybe this could be addressed with a pair of wakeup quirks, one for suspend,
> > another for resume. An optional genpd field could be added to struct
> > xhci_plat_priv. The wakeup quirks would set/clear GENPD_FLAG_ACTIVE_WAKEUP
> > of the genpd.
> >
> > Does the above sound more palatable?
> 
> I don't get why you need quirk flags. All you're doing here is:
> 
> 	if (usb_wakeup_enabled_descendants(hcd->self.root_hub))
>         	genpd->flags |= GENPD_FLAG_ACTIVE_WAKEUP;
> 
> If you move this test to xhci_suspend(), you shouldn't need all the
> magic, right?

Right, the quirks shouldn't be necessary if setting/clearing the genpd
flag is the right thing to do for any controller that sets the genpd
field in _priv, which probably is the case.