usb: dwc3: Enable usb2 LPM only when connected as usb2.0

Synopsys says:
The HIRD Threshold field must be set to ‘0’ when the device core is
operating in super speed mode.

This patch implements above statement.

Cc: <stable@vger.kernel.org> # v3.6 v3.7 v3.8
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -2154,6 +2154,23 @@ static void dwc3_gadget_conndone_interrupt(struct dwc3 *dwc)
 		break;
 	}
 
+	/* Enable USB2 LPM Capability */
+
+	if ((dwc->revision > DWC3_REVISION_194A)
+			&& (speed != DWC3_DCFG_SUPERSPEED)) {
+		reg = dwc3_readl(dwc->regs, DWC3_DCFG);
+		reg |= DWC3_DCFG_LPM_CAP;
+		dwc3_writel(dwc->regs, DWC3_DCFG, reg);
+
+		reg = dwc3_readl(dwc->regs, DWC3_DCTL);
+		reg &= ~(DWC3_DCTL_HIRD_THRES_MASK | DWC3_DCTL_L1_HIBER_EN);
+
+		/* TODO: This should be configurable */
+		reg |= DWC3_DCTL_HIRD_THRES(28);
+
+		dwc3_writel(dwc->regs, DWC3_DCTL, reg);
+	}
+
 	/* Recent versions support automatic phy suspend and don't need this */
 	if (dwc->revision < DWC3_REVISION_194A) {
 		/* Suspend unneeded PHY */
@@ -2460,20 +2477,8 @@ int dwc3_gadget_init(struct dwc3 *dwc)
 			DWC3_DEVTEN_DISCONNEVTEN);
 	dwc3_writel(dwc->regs, DWC3_DEVTEN, reg);
 
-	/* Enable USB2 LPM and automatic phy suspend only on recent versions */
+	/* automatic phy suspend only on recent versions */
 	if (dwc->revision >= DWC3_REVISION_194A) {
-		reg = dwc3_readl(dwc->regs, DWC3_DCFG);
-		reg |= DWC3_DCFG_LPM_CAP;
-		dwc3_writel(dwc->regs, DWC3_DCFG, reg);
-
-		reg = dwc3_readl(dwc->regs, DWC3_DCTL);
-		reg &= ~(DWC3_DCTL_HIRD_THRES_MASK | DWC3_DCTL_L1_HIBER_EN);
-
-		/* TODO: This should be configurable */
-		reg |= DWC3_DCTL_HIRD_THRES(28);
-
-		dwc3_writel(dwc->regs, DWC3_DCTL, reg);
-
 		dwc3_gadget_usb2_phy_suspend(dwc, false);
 		dwc3_gadget_usb3_phy_suspend(dwc, false);
 	}