usb: dwc3: gadget: Handle DEV_TXF_FLUSH_BYPASS capability

DWC_usb32 IP introduces a new behavior when handling NoStream event for
IN endpoints. If the controller is capable of DEV_TXF_FLUSH_BYPASS, then
the driver does not need to force to restart stream for IN endpoints.
The controller will generate ERDY and restart the stream periodically.
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/65c3070c666cd6b8beeee62d7f8e3e704ebf2d32.1619134559.git.Thinh.Nguyen@synopsys.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/core.h

@@ -379,6 +379,9 @@
 #define DWC3_GHWPARAMS7_RAM1_DEPTH(n)	((n) & 0xffff)
 #define DWC3_GHWPARAMS7_RAM2_DEPTH(n)	(((n) >> 16) & 0xffff)
 
+/* Global HWPARAMS9 Register */
+#define DWC3_GHWPARAMS9_DEV_TXF_FLUSH_BYPASS	BIT(0)
+
 /* Global Frame Length Adjustment Register */
 #define DWC3_GFLADJ_30MHZ_SDBND_SEL		BIT(7)
 #define DWC3_GFLADJ_30MHZ_MASK			0x3f

drivers/usb/dwc3/gadget.c

@@ -730,8 +730,16 @@ static int __dwc3_gadget_ep_enable(struct dwc3_ep *dep, unsigned int action)
 			 * All stream eps will reinitiate stream on NoStream
 			 * rejection until we can determine that the host can
 			 * prime after the first transfer.
+			 *
+			 * However, if the controller is capable of
+			 * TXF_FLUSH_BYPASS, then IN direction endpoints will
+			 * automatically restart the stream without the driver
+			 * initiation.
 			 */
-			dep->flags |= DWC3_EP_FORCE_RESTART_STREAM;
+			if (!dep->direction ||
+			    !(dwc->hwparams.hwparams9 &
+			      DWC3_GHWPARAMS9_DEV_TXF_FLUSH_BYPASS))
+				dep->flags |= DWC3_EP_FORCE_RESTART_STREAM;
 		}
 	}