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Message-ID: <shpn2wf64trpnulc7dsyyc76mafeila3amxl53wh4ksmtv2jte@3lccqv6wz72q>
Date: Tue, 10 Jun 2025 20:23:17 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
Cc: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] usb: dwc3: qcom: Implement glue callbacks to
facilitate runtime suspend
On Tue, Jun 10, 2025 at 10:06:24PM +0530, Krishna Kurapati wrote:
>
>
> On 6/10/2025 4:28 PM, Dmitry Baryshkov wrote:
> > On Tue, Jun 10, 2025 at 02:43:55PM +0530, Krishna Kurapati wrote:
> > > On Qualcomm DWC3 dual-role controllers, the conndone/disconnect events in
> > > device mode are generated by controller when software writes to QSCRATCH
> > > registers in Qualcomm Glue layer rather than the vbus line being routed to
> > > dwc3 core IP for it to recognize and generate these events.
> > >
> > > UTMI_OTG_VBUS_VALID bit of QSCRATCH_HS_PHY_CTRL register needs to be set
> > > to generate a connection done event and to be cleared for the controller to
> > > generate a disconnect event during cable removal. When the disconnect is
> > > not generated upon cable removal, the "connected" flag of dwc3 is left
> > > marked as "true" and it blocks suspend routines and for that to happen upon
> > > cable removal, the cable disconnect notification coming in via set_role
> > > call need to be provided to the Qualcomm glue layer as well.
> > >
> > > Currently, the way DWC3 core and Qualcomm legacy glue driver are designed,
> > > there is no mechanism through which the DWC3 core can notify the Qualcomm
> > > glue layer of any role changes which it receives via role switch. To
> > > register these glue callbacks at probe time, for enabling core to notify
> > > glue layer, the legacy Qualcomm driver has no way to find out when the
> > > child driver probe was successful since it does not check for the same
> > > during of_platform_populate.
> > >
> > > Hence implement the following glue callbacks for flattened Qualcomm glue
> > > driver:
> > >
> > > 1. set_role: To pass role switching information from drd layer to glue.
> > > This information is needed to identify NONE/DEVICE mode switch and modify
> > > QSCRATCH to generate connect-done event on device mode entry and disconnect
> > > event on cable removal in device mode.
> > >
> > > 2. run_stop: When booting up in device mode, if autouspend is enabled and
> > > userspace doesn't write UDC on boot, controller enters autosuspend. After
> > > this, if the userspace writes to UDC in the future, run_stop notifier is
> > > required to enable UTMI_OTG_VBUS_VALID of QSCRATCH so that connect done
> > > event is generated after run_stop(1) is done to finish enumeration.
> > >
> > > Signed-off-by: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
> > > ---
> > > drivers/usb/dwc3/dwc3-qcom.c | 82 ++++++++++++++++++++++++++++++++----
> > > 1 file changed, 73 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> > > index ca7e1c02773a..d40b52e2ba01 100644
> > > --- a/drivers/usb/dwc3/dwc3-qcom.c
> > > +++ b/drivers/usb/dwc3/dwc3-qcom.c
> > > @@ -89,6 +89,12 @@ struct dwc3_qcom {
> > > bool pm_suspended;
> > > struct icc_path *icc_path_ddr;
> > > struct icc_path *icc_path_apps;
> > > +
> > > + /*
> > > + * Current role changes via usb_role_switch_set_role callback protected
> > > + * internally by mutex lock.
> > > + */
> > > + enum usb_role current_role;
> > > };
> > > #define to_dwc3_qcom(d) container_of((d), struct dwc3_qcom, dwc)
> > > @@ -118,9 +124,9 @@ static inline void dwc3_qcom_clrbits(void __iomem *base, u32 offset, u32 val)
> > > }
> > > /*
> > > - * TODO: Make the in-core role switching code invoke dwc3_qcom_vbus_override_enable(),
> > > - * validate that the in-core extcon support is functional, and drop extcon
> > > - * handling from the glue
> > > + * TODO: Validate that the in-core extcon support is functional, and drop
> > > + * extcon handling from the glue. Make in-core extcon invoke
> > > + * dwc3_qcom_vbus_override_enable()
> > > */
> > > static void dwc3_qcom_vbus_override_enable(struct dwc3_qcom *qcom, bool enable)
> > > {
> > > @@ -641,6 +647,53 @@ static int dwc3_qcom_setup_irq(struct dwc3_qcom *qcom, struct platform_device *p
> > > return 0;
> > > }
> > > +static void dwc3_qcom_set_role_notifier(struct dwc3 *dwc, enum usb_role next_role)
> > > +{
> > > + struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
> > > +
> > > + if (qcom->current_role == next_role)
> > > + return;
> > > +
> > > + if (pm_runtime_resume_and_get(qcom->dev) < 0) {
> > > + dev_dbg(qcom->dev, "Failed to resume device\n");
> > > + return;
> > > + }
> > > +
> > > + if (qcom->current_role == USB_ROLE_DEVICE &&
> > > + next_role != USB_ROLE_DEVICE)
> > > + dwc3_qcom_vbus_override_enable(qcom, false);
> > > + else if ((qcom->current_role != USB_ROLE_DEVICE) &&
> > > + (next_role == USB_ROLE_DEVICE))
> > > + dwc3_qcom_vbus_override_enable(qcom, true);
> > > +
> > > + pm_runtime_mark_last_busy(qcom->dev);
> > > + pm_runtime_put_sync(qcom->dev);
> > > +
> > > + qcom->current_role = next_role;
> >
> > How is it protected by the mutex? Which mutex?
> >
>
> I see a mutex lock in usb_role_switch_set_role() that invokes set role. I
> think that should be sufficient here.
Please add a comment to the source code.
--
With best wishes
Dmitry
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