[PATCH v3] usb: dwc3: qcom: check for hcd in dwc3_qcom_read_usb2_speed

[Prashanth K <prashanth.k@oss.qualcomm.com>]

Currently dwc->xhci is not cleared if xhci_plat_probe() fails. During
system suspend, dwc3_qcom_read_usb2_speed() checks dwc->xhci and assumes
xhci is initialised. Since the probe failed, hcd will be null, and the
subsequent access results in a NULL pointer dereference

Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000058

Call trace:
  dwc3_qcom_pm_suspend
  dpm_run_callback
  device_suspend
  dpm_suspend
  dpm_suspend_start
  suspend_devices_and_enter
  pm_suspend

Explicitly check the hcd pointer in dwc3_qcom_read_usb2_speed
before accessing it.

Fixes: 6895ea55c385 ("usb: dwc3: qcom: Configure wakeup interrupts during suspend")
Signed-off-by: Prashanth K <prashanth.k@oss.qualcomm.com>
---
Changes in v3: 
 - Initialised udev to null, as suggested by sashiko bot.
 - Link to v2: https://lore.kernel.org/all/20261022044748.2303528-1-prashanth.k@oss.qualcomm.com/ 

Changes in v2:
 - Added null pointer check in dwc3-qcom.c instead of marking xhci as null in host.c
 - Link to v1: https://lore.kernel.org/all/20261014105711.1708244-1-prashanth.k@oss.qualcomm.com

 drivers/usb/dwc3/dwc3-qcom.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index ac68b4218b56..e4bf0d5fc9f1 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -231,7 +231,7 @@ static bool dwc3_qcom_is_host(struct dwc3_qcom *qcom)
 
 static enum usb_device_speed dwc3_qcom_read_usb2_speed(struct dwc3_qcom *qcom, int port_index)
 {
-	struct usb_device *udev;
+	struct usb_device *udev = NULL;
 	struct usb_hcd __maybe_unused *hcd;
 	struct dwc3 *dwc = &qcom->dwc;
 
@@ -241,9 +241,8 @@ static enum usb_device_speed dwc3_qcom_read_usb2_speed(struct dwc3_qcom *qcom, i
 	hcd = platform_get_drvdata(dwc->xhci);
 
 #ifdef CONFIG_USB
-	udev = usb_hub_find_child(hcd->self.root_hub, port_index + 1);
-#else
-	udev = NULL;
+	if (hcd)
+		udev = usb_hub_find_child(hcd->self.root_hub, port_index + 1);
 #endif
 	if (!udev)
 		return USB_SPEED_UNKNOWN;
-- 
2.34.1