usb: dwc3: core: Skip setting event buffers for host only controllers

On some SoC's like SA8295P where the tertiary controller is host-only
capable, GEVTADDRHI/LO, GEVTSIZ, GEVTCOUNT registers are not accessible.
Trying to access them leads to a crash.

For DRD/Peripheral supported controllers, event buffer setup is done
again in gadget_pullup. Skip setup or cleanup of event buffers if
controller is host-only capable.
Suggested-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Krishna Kurapati <quic_kriskura@quicinc.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Bjorn Andersson <andersson@kernel.org>
Tested-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20240420044901.884098-4-quic_kriskura@quicinc.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/core.c

@@ -486,6 +486,13 @@ static void dwc3_free_event_buffers(struct dwc3 *dwc)
 static int dwc3_alloc_event_buffers(struct dwc3 *dwc, unsigned int length)
 {
 	struct dwc3_event_buffer *evt;
+	unsigned int hw_mode;
+
+	hw_mode = DWC3_GHWPARAMS0_MODE(dwc->hwparams.hwparams0);
+	if (hw_mode == DWC3_GHWPARAMS0_MODE_HOST) {
+		dwc->ev_buf = NULL;
+		return 0;
+	}
 
 	evt = dwc3_alloc_one_event_buffer(dwc, length);
 	if (IS_ERR(evt)) {
@@ -507,6 +514,9 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
 {
 	struct dwc3_event_buffer	*evt;
 
+	if (!dwc->ev_buf)
+		return 0;
+
 	evt = dwc->ev_buf;
 	evt->lpos = 0;
 	dwc3_writel(dwc->regs, DWC3_GEVNTADRLO(0),
@@ -524,6 +534,9 @@ void dwc3_event_buffers_cleanup(struct dwc3 *dwc)
 {
 	struct dwc3_event_buffer	*evt;
 
+	if (!dwc->ev_buf)
+		return;
+
 	evt = dwc->ev_buf;
 
 	evt->lpos = 0;