usb: dwc3: gadget: Ignore Packet Pending bit

Currently the controller handles single stream only. So, Ignore Packet
Pending bit for stream selection and don't search for another stream if
the host sends Data Packet with PP=0 (for OUT direction) or ACK with
NumP=0 and PP=0 (for IN direction). This slightly improves the stream
performance.
Acked-by: NFelipe Balbi <balbi@kernel.org>
Signed-off-by: NThinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/097ba9e104c143f7ba0195ebff29390ec3043692.1618282705.git.Thinh.Nguyen@synopsys.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/core.h

@@ -403,6 +403,7 @@
 #define DWC3_DCFG_NUMP(n)	(((n) >> DWC3_DCFG_NUMP_SHIFT) & 0x1f)
 #define DWC3_DCFG_NUMP_MASK	(0x1f << DWC3_DCFG_NUMP_SHIFT)
 #define DWC3_DCFG_LPM_CAP	BIT(22)
+#define DWC3_DCFG_IGNSTRMPP	BIT(23)
 
 /* Device Control Register */
 #define DWC3_DCTL_RUN_STOP	BIT(31)

drivers/usb/dwc3/gadget.c

@@ -2399,6 +2399,17 @@ static int __dwc3_gadget_start(struct dwc3 *dwc)
 
 	dwc3_gadget_setup_nump(dwc);
 
+	/*
+	 * Currently the controller handles single stream only. So, Ignore
+	 * Packet Pending bit for stream selection and don't search for another
+	 * stream if the host sends Data Packet with PP=0 (for OUT direction) or
+	 * ACK with NumP=0 and PP=0 (for IN direction). This slightly improves
+	 * the stream performance.
+	 */
+	reg = dwc3_readl(dwc->regs, DWC3_DCFG);
+	reg |= DWC3_DCFG_IGNSTRMPP;
+	dwc3_writel(dwc->regs, DWC3_DCFG, reg);
+
 	/* Start with SuperSpeed Default */
 	dwc3_gadget_ep0_desc.wMaxPacketSize = cpu_to_le16(512);