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Date:   Fri, 15 Apr 2022 17:30:26 -0700
From:   Matthias Kaehlcke <mka@chromium.org>
To:     "Sandeep Maheswaram (Temp)" <quic_c_sanm@quicinc.com>
Cc:     Pavan Kondeti <quic_pkondeti@quicinc.com>,
        Rob Herring <robh+dt@kernel.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Felipe Balbi <balbi@kernel.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Doug Anderson <dianders@chromium.org>,
        Mathias Nyman <mathias.nyman@intel.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        quic_ppratap@quicinc.com, quic_kriskura@quicinc.com,
        quic_vpulyala@quicinc.com
Subject: Re: [PATCH v13 2/6] usb: dwc3: core: Host wake up support from
 system suspend
Message-ID: <YloOIqqys3SgVAcW@google.com>
References: <1649704614-31518-1-git-send-email-quic_c_sanm@quicinc.com>
 <1649704614-31518-3-git-send-email-quic_c_sanm@quicinc.com>
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 <36d22ad7-7f11-2f63-cd68-5d564476161e@quicinc.com>
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 <259c9e87-a52e-c063-7901-2c6decd42675@quicinc.com>
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 <ee38105f-e2f4-4e40-3c89-224301f1eb12@quicinc.com>
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On Thu, Apr 14, 2022 at 11:27:31AM +0530, Sandeep Maheswaram (Temp) wrote:
> Hi Matthias,
> 
> On 4/13/2022 9:26 PM, Matthias Kaehlcke wrote:
> > On Wed, Apr 13, 2022 at 02:38:33PM +0530, Sandeep Maheswaram (Temp) wrote:
> > > Hi Matthias,
> > > 
> > > On 4/13/2022 12:35 AM, Matthias Kaehlcke wrote:
> > > > On Tue, Apr 12, 2022 at 12:08:02PM +0530, Sandeep Maheswaram (Temp) wrote:
> > > > > Hi Pavan,
> > > > > 
> > > > > On 4/12/2022 10:30 AM, Pavan Kondeti wrote:
> > > > > > Hi Sandeep,
> > > > > > 
> > > > > > On Tue, Apr 12, 2022 at 10:16:39AM +0530, Sandeep Maheswaram (Temp) wrote:
> > > > > > > Hi Matthias,
> > > > > > > 
> > > > > > > On 4/12/2022 2:24 AM, Matthias Kaehlcke wrote:
> > > > > > > > On Tue, Apr 12, 2022 at 12:46:50AM +0530, Sandeep Maheswaram wrote:
> > > > > > > > > During suspend read the status of all port and set hs phy mode
> > > > > > > > > based on current speed. Use this hs phy mode to configure wakeup
> > > > > > > > > interrupts in qcom glue driver.
> > > > > > > > > 
> > > > > > > > > Check wakep-source property for dwc3 core node to set the
> > > > > > > > s/wakep/wakeup/
> > > > > > > Okay. Will update in next version.
> > > > > > > > > wakeup capability. Drop the device_init_wakeup call from
> > > > > > > > > runtime suspend and resume.
> > > > > > > > > 
> > > > > > > > > Also check during suspend if any wakeup capable devices are
> > > > > > > > > connected to the controller (directly or through hubs), if there
> > > > > > > > > are none set a flag to indicate that the PHY is powered
> > > > > > > > > down during suspend.
> > > > > > > > > 
> > > > > > > > > Signed-off-by: Sandeep Maheswaram <quic_c_sanm@quicinc.com>
> > > > > > > > > ---
> > > > > > > > A per-patch change log would be really helpful for reviewers, even
> > > > > > > > if it doesn't include older versions.
> > > > > > > Okay. Will update in next version.
> > > > > > > > >     drivers/usb/dwc3/core.c | 33 ++++++++++++++++++++-------------
> > > > > > > > >     drivers/usb/dwc3/core.h |  4 ++++
> > > > > > > > >     drivers/usb/dwc3/host.c | 25 +++++++++++++++++++++++++
> > > > > > > > >     3 files changed, 49 insertions(+), 13 deletions(-)
> > > > > > > > > 
> > > > > > > > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > > > > > > > > index 1170b80..effaa43 100644
> > > > > > > > > --- a/drivers/usb/dwc3/core.c
> > > > > > > > > +++ b/drivers/usb/dwc3/core.c
> > > > > > > > > @@ -32,6 +32,7 @@
> > > > > > > > >     #include <linux/usb/gadget.h>
> > > > > > > > >     #include <linux/usb/of.h>
> > > > > > > > >     #include <linux/usb/otg.h>
> > > > > > > > > +#include <linux/usb/hcd.h>
> > > > > > > > >     #include "core.h"
> > > > > > > > >     #include "gadget.h"
> > > > > > > > > @@ -1723,6 +1724,7 @@ static int dwc3_probe(struct platform_device *pdev)
> > > > > > > > >     	platform_set_drvdata(pdev, dwc);
> > > > > > > > >     	dwc3_cache_hwparams(dwc);
> > > > > > > > > +	device_init_wakeup(&pdev->dev, of_property_read_bool(dev->of_node, "wakeup-source"));
> > > > > > > > >     	spin_lock_init(&dwc->lock);
> > > > > > > > >     	mutex_init(&dwc->mutex);
> > > > > > > > > @@ -1865,6 +1867,7 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
> > > > > > > > >     {
> > > > > > > > >     	unsigned long	flags;
> > > > > > > > >     	u32 reg;
> > > > > > > > > +	struct usb_hcd  *hcd = platform_get_drvdata(dwc->xhci);
> > > > > > > > >     	switch (dwc->current_dr_role) {
> > > > > > > > >     	case DWC3_GCTL_PRTCAP_DEVICE:
> > > > > > > > > @@ -1877,10 +1880,7 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
> > > > > > > > >     		dwc3_core_exit(dwc);
> > > > > > > > >     		break;
> > > > > > > > >     	case DWC3_GCTL_PRTCAP_HOST:
> > > > > > > > > -		if (!PMSG_IS_AUTO(msg)) {
> > > > > > > > > -			dwc3_core_exit(dwc);
> > > > > > > > > -			break;
> > > > > > > > > -		}
> > > > > > > > > +		dwc3_check_phy_speed_mode(dwc);
> > > > > > > > >     		/* Let controller to suspend HSPHY before PHY driver suspends */
> > > > > > > > >     		if (dwc->dis_u2_susphy_quirk ||
> > > > > > > > > @@ -1896,6 +1896,16 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
> > > > > > > > >     		phy_pm_runtime_put_sync(dwc->usb2_generic_phy);
> > > > > > > > >     		phy_pm_runtime_put_sync(dwc->usb3_generic_phy);
> > > > > > > > > +
> > > > > > > > > +		if (!PMSG_IS_AUTO(msg)) {
> > > > > > > > > +			if (device_may_wakeup(dwc->dev) &&
> > > > > > > > > +			    usb_wakeup_enabled_descendants(hcd->self.root_hub)) {
> > > > > > > > You did not answer my question on v12, reposting it:
> > > > > > > > 
> > > > > > > >      Did you ever try whether you could use device_children_wakeup_capable() from
> > > > > > > >      [1] instead of usb_wakeup_enabled_descendants()?
> > > > > > > > 
> > > > > > > >      [1] https://patchwork.kernel.org/project/linux-usb/patch/1635753224-23975-2-git-send-email-quic_c_sanm@quicinc.com/#24566065
> > > > > > > Sorry ..I have replied in mail yesterday but it is not showing up in
> > > > > > > patchwork link.
> > > > > > > 
> > > > > > > Tried with  device_children_wakeup_capable(dwc->dev) instead of
> > > > > > > usb_wakeup_enabled_descendants and it always returns true even
> > > > > > > 
> > > > > > > when no devices are connected.
> > > > > > > 
> > > > > > What do you mean by when no devices are connected? There is always
> > > > > > root hub connected and we should not power down the DWC3 here even
> > > > > > when remote wakeup for root hub is enabled. Essentially
> > > > > > usb_wakeup_enabled_descendants() returns true even without any
> > > > > > physical devices connected.
> > > > > > 
> > > > > > What does device_children_wakeup_capable() do? Sorry, I could not
> > > > > > find this function definition.
> > > > > > 
> > > > > > Thanks,
> > > > > > Pavan
> > > > > usb_wakeup_enabled_descendants() doesn't consider hubs. It only returns true if any devices
> > > > > are connected with wakeup capability apart from hubs.
> > > > Actually it considers hubs:
> > > > 
> > > > unsigned usb_wakeup_enabled_descendants(struct usb_device *udev)
> > > > {
> > > > 	struct usb_hub *hub = usb_hub_to_struct_hub(udev);
> > > > 
> > > > 	return udev->do_remote_wakeup +
> > > > 		(hub ? hub->wakeup_enabled_descendants : 0);
> > > > }
> > > > 
> > > > 'udev' may or may not be a hub, if 'do_remote_wakeup' is set then the
> > > > device is considered a wakeup enabled descendant.
> > > > 
> > > > And for system suspebd 'do_remote_wakeup' is set based on the wakeup
> > > > config of the device:
> > > > 
> > > > static void choose_wakeup(struct usb_device *udev, pm_message_t msg)
> > > > {
> > > > 	...
> > > > 	w = device_may_wakeup(&udev->dev);
> > > > 	...
> > > > 	udev->do_remote_wakeup = w;
> > > > }
> > > > 
> > > > I checked on three systems with different Linux distributions, on all of
> > > > the wakeup flag of a connected hub is 'disabled'. Wakeup still works, so
> > > > apparently that flag doesn't really have an impact for child ports.
> > > > 
> > > > > If we consider hubs also dwc3 core exit and phy exit will never be called.
> > > > > 
> > > > > device_children_wakeup_capable() implementation was shared by Matthias in below thread
> > > > > https://patchwork.kernel.org/project/linux-usb/patch/1635753224-23975-2-git-send-email-quic_c_sanm@quicinc.com/#24566065
> > > > > 
> > > > > Probably device_children_wakeup_capable() is returning true because it considers hubs also.
> > > > I thought I did a basic test when I sent the patch, I did another (?) one
> > > > with v13 of your patch set. In this tests with a hub connected the
> > > > function returns true when an HID device is connected, and false when
> > > > nothing is connected. The wakeup flag of the hub is disabled (default).
> > > > 
> > > > Sandeep, are the wakeup flags of the child hub(s) set to 'enabled' on
> > > > the system you tested on?
> > > The wakeup flags of hub is 'disabled' on system I tested.
> > > 
> > > What is the input param you are giving to device_children_wakeup_capable() function ?
> > I passed '&hcd->self.root_hub->dev'
> 
> Thanks. It is working with this change device_children_wakeup_capable
> (&hcd->self.root_hub->dev).
> 
> But I am not sure if it is better than usb_wakeup_enabled_descendants. Still
> we are accessing xhci layer
> 
> from dwc which Felipe suggested to avoid.

True, it still needs access to the data structure(s), even though it doesn't
use a USB specific API.

Would be good to get feedback from Felipe on the current approach in general,
we haven't heard from him in some time.