usb: dwc3: Workaround for irq mask issue

This is a workaround for STAR 9000961433 which affects only version
3.00a of the DWC_usb3 core. This prevents the controller interrupt from
being masked while handling events. Enabling interrupt moderation allows
us to work around this issue because once the GEVNTCOUNT.count is
written the IRQ is immediately deasserted and won't be asserted again
until GEVNTCOUNT.EHB is cleared.
Signed-off-by: NJohn Youn <johnyoun@synopsys.com>
Signed-off-by: NFelipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/core.c

@@ -1004,6 +1004,17 @@ static void dwc3_check_params(struct dwc3 *dwc)
 		dwc->imod_interval = 0;
 	}
 
+	/*
+	 * Workaround for STAR 9000961433 which affects only version
+	 * 3.00a of the DWC_usb3 core. This prevents the controller
+	 * interrupt from being masked while handling events. IMOD
+	 * allows us to work around this issue. Enable it for the
+	 * affected version.
+	 */
+	if (!dwc->imod_interval &&
+	    (dwc->revision == DWC3_REVISION_300A))
+		dwc->imod_interval = 1;
+
 	/* Check the maximum_speed parameter */
 	switch (dwc->maximum_speed) {
 	case USB_SPEED_LOW: