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Message-ID: <83c54b3e-8e31-4ca1-9ca6-31703211d507@oss.qualcomm.com>
Date: Wed, 6 Aug 2025 12:32:09 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krishna Kurapati <krishna.kurapati@....qualcomm.com>,
Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Mathias Nyman <mathias.nyman@...el.com>,
Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] usb: dwc3: qcom: Implement glue callbacks to
facilitate runtime suspend
On 8/6/25 11:58 AM, 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 | 80 +++++++++++++++++++++++++++++++-----
> 1 file changed, 70 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index a7eaefaeec4d..5195267cd34d 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
> @@ -83,6 +83,8 @@ struct dwc3_qcom {
> bool pm_suspended;
> struct icc_path *icc_path_ddr;
> struct icc_path *icc_path_apps;
> +
> + enum usb_role current_role;
> };
>
> #define to_dwc3_qcom(d) container_of((d), struct dwc3_qcom, dwc)
> @@ -111,10 +113,6 @@ static inline void dwc3_qcom_clrbits(void __iomem *base, u32 offset, u32 val)
> readl(base + offset);
> }
>
> -/*
> - * TODO: Make the in-core role switching code invoke dwc3_qcom_vbus_override_enable(),
> - * validate that the in-core extcon support is functional
> - */
> static void dwc3_qcom_vbus_override_enable(struct dwc3_qcom *qcom, bool enable)
> {
> if (enable) {
> @@ -560,6 +558,57 @@ 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) {
no need for the "< 0":
"""
Return 0 if the runtime PM usage counter of @dev has been
incremented or a negative error code otherwise.
"""
> + dev_dbg(qcom->dev, "Failed to resume device\n");
This probably belongs in the suspend/resume calls themselves
> + return;
> + }
> +
> + if (qcom->current_role == USB_ROLE_DEVICE &&
> + next_role != USB_ROLE_DEVICE)
The second part is unnecessary because the first if-condition in this
function ensures it
> + dwc3_qcom_vbus_override_enable(qcom, false);
> + else if ((qcom->current_role != USB_ROLE_DEVICE) &&
> + (next_role == USB_ROLE_DEVICE))
similarly here
meaning this can become
dwc3_qcom_vbus_override_enable(qcom, next_role == USB_ROLE_DEVICE)
(I'm not sure if it's easier to read, up to you)
> + dwc3_qcom_vbus_override_enable(qcom, true);
> +
> + pm_runtime_mark_last_busy(qcom->dev);
> + pm_runtime_put_sync(qcom->dev);
> +
> + /*
> + * Current role changes via usb_role_switch_set_role callback protected
> + * internally by mutex lock.
> + */
> + qcom->current_role = next_role;
> +}
> +
> +static void dwc3_qcom_run_stop_notifier(struct dwc3 *dwc, bool is_on)
> +{
> + struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
> +
> + /*
> + * When autosuspend is enabled and controller goes to suspend
> + * after removing UDC from userspace, the next UDC write needs
> + * setting of QSCRATCH VBUS_VALID to "1" to generate a connect
> + * done event.
> + */
> + if (!is_on)
> + return;
> +
> + dwc3_qcom_vbus_override_enable(qcom, is_on);
this argument logically becomes true, always
> + pm_runtime_mark_last_busy(qcom->dev);
> +}
> +
> +struct dwc3_glue_ops dwc3_qcom_glue_ops = {
> + .pre_set_role = dwc3_qcom_set_role_notifier,
> + .pre_run_stop = dwc3_qcom_run_stop_notifier,
> +};
> +
> static int dwc3_qcom_probe(struct platform_device *pdev)
> {
> struct dwc3_probe_data probe_data = {};
> @@ -636,6 +685,23 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
> if (ignore_pipe_clk)
> dwc3_qcom_select_utmi_clk(qcom);
>
> + qcom->mode = usb_get_dr_mode(dev);
> +
> + if (qcom->mode == USB_DR_MODE_HOST) {
> + qcom->current_role = USB_ROLE_HOST;
> + } else if (qcom->mode == USB_DR_MODE_PERIPHERAL) {
> + qcom->current_role = USB_ROLE_DEVICE;
> + dwc3_qcom_vbus_override_enable(qcom, true);
> + } else {
> + if ((device_property_read_bool(dev, "usb-role-switch")) &&
> + (usb_get_role_switch_default_mode(dev) == USB_DR_MODE_HOST))
currently this will never be true on any qcom dt ("role-switch-default-mode" is
not present anywhere)
> + qcom->current_role = USB_ROLE_HOST;
> + else
> + qcom->current_role = USB_ROLE_DEVICE;
> + }
> +
> + qcom->dwc.glue_ops = &dwc3_qcom_glue_ops;
> +
Konrad
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