Re: [PATCH v2 2/4] usb: dwc3: qcom: Implement glue callbacks to facilitate runtime suspend

[Krishna Kurapati]

On 6/24/2025 5:02 AM, Thinh Nguyen wrote:
> On Tue, Jun 10, 2025, 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@xxxxxxxxxxxxxxxx>
> > ---
> >   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;
>
> Can we just track the current role through dwc3 core instead of an
> addition field in the glue?

Core caches only mode. We need ROLE NONE to identify cable connect. So 
adding that in glue to keep track.

Regards,
Krishna,