if_dwc: enable RX checksum offload feature

We claim support in ifcaps, but don't actually enable it.

PR:		263886
Reviewed by:	manu
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D35498

sys/dev/dwc/if_dwc.c

@@ -518,6 +518,20 @@ dwc_enable_mac(struct dwc_softc *sc, bool enable)
 	WRITE4(sc, MAC_CONFIGURATION, reg);
 }
 
+static void
+dwc_enable_csum_offload(struct dwc_softc *sc)
+{
+	uint32_t reg;
+
+	DWC_ASSERT_LOCKED(sc);
+	reg = READ4(sc, MAC_CONFIGURATION);
+	if ((if_getcapenable(sc->ifp) & IFCAP_RXCSUM) != 0)
+		reg |= CONF_IPC;
+	else
+		reg &= ~CONF_IPC;
+	WRITE4(sc, MAC_CONFIGURATION, reg);
+}
+
 static void
 dwc_get_hwaddr(struct dwc_softc *sc, uint8_t *hwaddr)
 {
@@ -1163,6 +1177,7 @@ dwc_init_locked(struct dwc_softc *sc)
 	dwc_setup_rxfilter(sc);
 	dwc_setup_core(sc);
 	dwc_enable_mac(sc, true);
+	dwc_enable_csum_offload(sc);
 	dwc_init_dma(sc);
 
 	if_setdrvflagbits(ifp, IFF_DRV_RUNNING, IFF_DRV_OACTIVE);
@@ -1261,6 +1276,12 @@ dwc_ioctl(if_t ifp, u_long cmd, caddr_t data)
 			if_sethwassistbits(ifp, CSUM_IP | CSUM_UDP | CSUM_TCP, 0);
 		else
 			if_sethwassistbits(ifp, 0, CSUM_IP | CSUM_UDP | CSUM_TCP);
+
+		if (if_getdrvflags(ifp) & IFF_DRV_RUNNING) {
+			DWC_LOCK(sc);
+			dwc_enable_csum_offload(sc);
+			DWC_UNLOCK(sc);
+		}
 		break;
 
 	default:

sys/dev/dwc/if_dwc.h

@@ -48,6 +48,7 @@
 #define	 CONF_PS		(1 << 15)	/* GMII/MII */
 #define	 CONF_FES		(1 << 14)	/* MII speed select */
 #define	 CONF_DM		(1 << 11)	/* Full Duplex Enable */
+#define	 CONF_IPC		(1 << 10)	/* IPC checksum offload */
 #define	 CONF_ACS		(1 << 7)
 #define	 CONF_TE		(1 << 3)
 #define	 CONF_RE		(1 << 2)