On Tue, Aug 12, 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 | 78 +++++++++++++++++++++++++++++++-----
1 file changed, 68 insertions(+), 10 deletions(-)
diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index a7eaefaeec4d..d89fbb1d8994 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 +558,55 @@ 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)
Minor nit: There's no notifier here, can we rename to
dwc3_qcom_pre_set_role() for clarity?
+{
+ struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
+
+ if (qcom->current_role == next_role)
+ return;
+
+ if (pm_runtime_resume_and_get(qcom->dev)) {
+ dev_dbg(qcom->dev, "Failed to resume device\n");
Minor nit: should this be dev_err?
+ return;
+ }
+
+ if (qcom->current_role == USB_ROLE_DEVICE)
+ dwc3_qcom_vbus_override_enable(qcom, false);
+ else if (qcom->current_role != USB_ROLE_DEVICE)
+ 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)
Minor nit: can we rename to dwc3_qcom_pre_run_stop()
+{
+ 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, true);
+ 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 +683,23 @@ 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);
Shouldn't you determine if there's connection before setting vbus valid?
There are a couple things that seems at odd to me:
1) Typically we use "vbus override" to describe the vbus control on host
to turn on/off vbus. Where as here, the vbus override is used for
vbus valid in device mode for vbus detection.
