usb: dwc2: WA for Full speed ISOC IN in DDMA mode.

By clearing NAK status of EP, core will send ZLP
to IN token and assert NAK interrupt relying
on TxFIFO status only.

The WA applies only to core versions from 2.72a
to 4.00a (including both). Also for FS_IOT_1.00a
and HS_IOT_1.00a.
Signed-off-by: Artur Petrosyan <arturp@synopsys.com>
Signed-off-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/core.h

@@ -985,6 +985,7 @@ struct dwc2_hsotg {
 
 	/* DWC OTG HW Release versions */
 #define DWC2_CORE_REV_2_71a	0x4f54271a
+#define DWC2_CORE_REV_2_72a     0x4f54272a
 #define DWC2_CORE_REV_2_80a	0x4f54280a
 #define DWC2_CORE_REV_2_90a	0x4f54290a
 #define DWC2_CORE_REV_2_91a	0x4f54291a
@@ -992,6 +993,7 @@ struct dwc2_hsotg {
 #define DWC2_CORE_REV_2_94a	0x4f54294a
 #define DWC2_CORE_REV_3_00a	0x4f54300a
 #define DWC2_CORE_REV_3_10a	0x4f54310a
+#define DWC2_CORE_REV_4_00a	0x4f54400a
 #define DWC2_FS_IOT_REV_1_00a	0x5531100a
 #define DWC2_HS_IOT_REV_1_00a	0x5532100a
 

drivers/usb/dwc2/gadget.c

@@ -3928,6 +3928,27 @@ static int dwc2_hsotg_ep_enable(struct usb_ep *ep,
 	if (index && !hs_ep->isochronous)
 		epctrl |= DXEPCTL_SETD0PID;
 
+	/* WA for Full speed ISOC IN in DDMA mode.
+	 * By Clear NAK status of EP, core will send ZLP
+	 * to IN token and assert NAK interrupt relying
+	 * on TxFIFO status only
+	 */
+
+	if (hsotg->gadget.speed == USB_SPEED_FULL &&
+	    hs_ep->isochronous && dir_in) {
+		/* The WA applies only to core versions from 2.72a
+		 * to 4.00a (including both). Also for FS_IOT_1.00a
+		 * and HS_IOT_1.00a.
+		 */
+		u32 gsnpsid = dwc2_readl(hsotg->regs + GSNPSID);
+
+		if ((gsnpsid >= DWC2_CORE_REV_2_72a &&
+		     gsnpsid <= DWC2_CORE_REV_4_00a) ||
+		     gsnpsid == DWC2_FS_IOT_REV_1_00a ||
+		     gsnpsid == DWC2_HS_IOT_REV_1_00a)
+			epctrl |= DXEPCTL_CNAK;
+	}
+
 	dev_dbg(hsotg->dev, "%s: write DxEPCTL=0x%08x\n",
 		__func__, epctrl);